Sherrell Greene on his Accomplishments and on Nuclear Safety

Sherrell Greene recently retired from ORNL after 33 years employment. Sherrell was ORNL's Director for Nuclear Technology Programs from 2004 through 2010, and Director of ORNL's Research Reactor Development Programs from 2010 through his retirement in 2011. A "relatively-complete" list of Dr Greene's professional publications can be found in his blog. A few weeks after Sherrell Greene's retirement from ORNL in September I meet with him for a preinterview. Subsequently I sent him a number of interview questions for his written responses. This is the first section of Sherrell Greene's responses to my questions. Greene has made conspicuous contributions to nuclear safety, and my first series of questions dealt with nuclear safety.

1. What do you view as your greatest accomplishment at ORNL?

I don’t think in terms of “greatest accomplishments”. Frankly, I’ve not given any consideration to my “greatest accomplishments” (smile)

Overall, I’m most gratified to have played a leadership role in maintaining and growing ORNL’s nuclear energy R&D programs during the past decade. When I left the Lab, ORNL’s nuclear energy R&D portfolio had grown to roughly $100M / yr for four federal agencies and the commercial nuclear industry.

Technically, several things come to mind: (1) the pioneering work we did in the early 1980’s in BWR severe accident analysis, (2) our work in the 90s on reactor-based weapons plutonium disposition that laid the technical foundation in Russia and in the US for disposition of excess weapons-grade plutonium, (3) the successful execution of the Coupled End-to-End Demonstration at the Radiochemical Engineering Development Center a few years ago in which we demonstrated the first reprocessing of LWR fuel and fabrication of mixed oxide fuel without separating pure plutonium, (4) the development of the Department of Energy’s Office of Nuclear Energy R&D Roadmap in 2008, (5) development of the OR-SAGE national electrical generation siting model, and (6) development of the Small advanced High Temperature Reactor (SmAHTR) fluoride salt cooled reactor concept. I found each of these challenging and rewarding, and feel blessed to have had an opportunity to engage in such a wide variety of endeavors. National laboratories are special places in terms of the breadth of opportunities afforded one with an entrepreneurial spirit.

Ultimately though, my greatest satisfaction came from the fantastic people I worked with, and building multi-disciplinary teams to tackle really tough challenges.
I don’t think in terms of “greatest accomplishments”. Frankly, I’ve not given any consideration to my “greatest accomplishments” (smile)

Ultimately though, my greatest satisfaction came from the fantastic people I worked with, and building multi-disciplinary teams to tackle really tough challenges.

2. What was your biggest disappointment at ORNL?

Probably my inability in recent years to convince Lab management to aggressively re- embrace its high temperature advanced reactor development legacy and aggressively pursue fluoride-salt cooled (FHR) and molten salt reactor (MSR) system concept development.

3. What do you believe is your most important contribution to Nuclear Safety?

Probably the work I did in BWR severe accident simulation and analysis in the 1980’s through the early 1990s. I was part of the team that conducted the first detailed analysis of unmitigated BWR station blackout and loss of decay heat removal sequences. The former work has been widely reference during the past few months since the Fukushima Dai-ichi events.

4. Would your ORNL peers agree with you, or would they point to other accomplishments?
I don’t know.

5. What other contributions have you made to nuclear safety?

I authored a report in 1984 (NUREG/CR-­2940) that had some impact on the direction of LWR severe accident code development (particularly MELCOR). To my knowledge, I was the first one to identify and characterize the potential role of BWR reactor buildings in severe accident mitigation. I also conducted the first port of reactor safety code (CONTAIN) to a supercomputer (ORNL’s CRAY-I at that time). This opened our eyes to the potential for advances in computing technology to revolutionize our understanding of reactor safety.

6. How do you view the performance of the Fukushima reactors from a nuclear safety perspective?

Well, I think the primary containments of Units 1-3 have held together remarkably well given the challenges presented to them. It’s a testament to their fundamental design.

7. What safety lessons can be learned from the Fukushima reactor events?

We will be learning lessons from the Fukushima event for years to come. As you know, the NRC has taken a first cut at identifying lessons learned and creating an action plan. However, there are a few observations that standout to me. I’ve discussed the on my blog, www.SustainableEnergyToday.blogspot.com. First, from a risk based design/analysis perspective – get your top event frequencies/probabilities right. In hindsight, it appears the probabilities of the grand earthquake and coupled tsunami were underestimated. Second, understand the potential for events at one unit (such as explosions) to damage another unit. Third, understand the implications of events that not only damage one or more units on a multi-unit site, but also render the surrounding area incapable of providing assistance to the site. Few, if any, probabilistic risk assessments to date have fully explored the last two issues. Fourth, there’s no substitute for defense- in-depth in plant design. BWRs have a remarkably diverse set of options for injecting water into the reactor and containment. Despite all of the system failures at Fukushima, it was this diversity that has allowed the plant operators to manage as well as they have. Lastly, train and think as if these accidents can happen. They do. I could go on and on, but the point is, there’s much to be learned – and much will be learned from Fukushima.

8. How can the Fukushima lessons be best applied to existing reactors?

We need to take a second look at how we develop and validate the basic event data for our PRA models. We need to take a second look at our fundamental assumptions regarding the independence of events in multi-unit sites. We need to re-evaluate the implicit assumption in almost all PRA’s, that the outside world can gain rapid access to the site to provide assistance. Potential plant backfits, operational procedures changes, and emergency response procedures changes need to be examined and high-value modification should be made. We need to re-evaluate, from the systems perspective, our requirements with regard to station battery lifetime, backup diesel-generator availability, and off-site power feed to the plants. I feel the value of dedicated BWR containment flooding systems that our team identified in the 1980s should be revisited.

9. How can the Fukushima lessons be applied in future reactor designs?

All of the observations I made earlier also apply to the design of future reactors. All reactor technologies (water cooled, or otherwise), have inherent vulnerabilities that must be addressed by a combination of system design features, operational protocols, and emergency planning.

10. Do you believe that current LWR designs, for example the Westinghouse AP- 1000 solve safety problems revealed by the Fukushima accidents?

There’s no doubt in my mind that more recent designs are more robust than older designs. This is the case both for BWRs and PWRs. That’s not a condemnation of older designs. It’s just evolutionary progress. The fact remains, of course, that water and over-heated zirconium-clad fuel do not peacefully coexist. The newer plants do incorporate a variety of design features that reduce the probability this situation will arise.

11. What other safety features would you like to see in future Light Water Reactor designs that are not included in current designs?

As you know, the key issue for reactor safety is extraction and rejection of the core’s decay heat so that the fuel and its containment boundaries are not damaged. A more robust fuel design would be wonderful. But it’s a long path (probably 10-20 years) for introduction of a new fuel in the LWR business. Most of the new LWR designs already provide passive mechanisms for flooding the reactor and containment in the event of a station blackout event. Though we’re learning that many of the fears we originally had about massive damage in the spent fuel pools at Fukushima were not realized, I think it’s a good idea to remove spent fuel from close proximity to the reactor as soon as practical after the fuel is discharged from the reactor.

I’m an advocate of a design philosophy called, “Irreducible Complexity”. It is a line of reasoning that states there is an optimal design point – in terms of system complexity – at which removal of a design feature or artifact will result in an unacceptable reduction in system functionality; while addition of a design artifact will not significantly improve system functionality. Old-fashioned mousetraps and clothespins are good examples of irreducibly complex systems. We’ve been trying without success to improve upon their design from the moment they were created. While Irreducible Complexity may not be achievable in the real world, I’ve found the thought process to be an invaluable Gedanken Experiment countless time during my career. So my hope is that future plants can pursue simplified design architectures. Alvin Weinberg told me one time he felt one of the two major contributors to the demise of the MSR was that it looked too much like a chemical plant to the traditional reactor community. They just couldn’t get comfortable with it. That’s a lesson worth remembering...

Another area I would like to see explored in future plants is the concept I call “Centurion Reactors”. A few years before Alvin Weinberg died, I had the privilege of spending the better part of an afternoon with him at his home in Oak Ridge. We discussed his career, his dreams, and his failures. During the later years of his life, he was passionate about the concept of “Immortal Reactors”. His idea was that commercial power plants are capitally-intensive investments that actually yield inter-generational benefits. Once their capital cost is amortized, today’s LWRs produce electricity at less than 5 cents / kilowatt- hr. That’s a huge benefit that lasts as long as the plant operates and accrues to its customers – the children and grandchildren of its builders. Before Dr. Weinberg died, he sent me his file on Immortal Reactors. After some thought, I concluded a realistic near- term goal would be to design nuclear power systems for an operating lifetime of 100 years. Thus the term “Centurion Reactors”. The entire plant would be designed by integrating design-for-life, design-for-maintenance, design-for-monitoring, and design- for-replacement technologies and architectures, with the goal of enabling the plants to be licensed for and operator for 100 years.

(Sherrell's web site can be found at, www.SherrellGreene.com.)

ORNL Offers a Brief Look at MSR/LFTR Economies

A recent ORNL report, Fast Spectrum Molten Salt Reactor Options, offers some insight into the cost lowering potential of MSR nuclear technology. Since Nuclear Green has always had an interest in the cost lowering potential of MSR technology, I intend to review the cost related information included in this report, while in some cases offering a context for that information.

The "Fast Spectrum" report does not offer and cost evaluation in terms of dollar costs, indeed this would not be possible. The report offers an overview of technical options, and no dollar cost evaluation is possible outside the context of a specific design project. The report acknowledges,

A confident assessment of the economic performance of an FS-MSR is not yet possible. Technology, regulatory requirements, and market conditions have changed significantly over the 40 years since the economic assessments accompanying the MSBR; therefore, the cost inferences drawn from the earlier work have such large error bands that they provide little guidance. Additionally, the neutron spectrum of the present evaluation alters the fuel cycle both in and outside the power plant site sufficiently that direct analogies to other reactor concepts are challenging. The most challenging aspect of reporting a cost for an FS-MSR, however, arises from the concept flexibility. A no-heavy-metal reprocessing design variant has a plant layout much different from that of a full-recycle plant intending to directly accept used LWR fuel as its fuel source. Similarly, a plant intending to produce gasoline as its primary product has an entirely different power cycle compared with an electricity generator.

Overall economic tendencies, however, can be estimated by comparing FS-MSR attributes with those of other nuclear power systems. A summary of FS-MSR attributes and their cost implications is provided in Table 2. A primary cost metric for any power plant is its thermal efficiency. FS-MSRs, as high- temperature power plants, are anticipated to have 45–48% thermal efficiencies, a 12–15% efficiency advantage over LWRs. As refueling for an FS-MSR would be performed on-line, the plant availability would be expected to eventually, once maintenance techniques were developed and matured, surpass that for an LWR.

Thus costs are evaluated in relationship to the cost of Light Water Reactor costs. For example, the absence of a fuel fabrication requirement would lower FMSR costs and indeed all MSR costs relative to LWRs

Other FMSR characteristics that would tend to lower capital costs noted by the Fast Spectrum report would include,

* No fuel handling equipment or pool storage facilities
* No irradiated cladding or matrix material in ultimate waste stream
* Large temperature reactivity coefficient
* No cladding- or matrix-based temperature limits in accident scenarios
* Safe shutdown possible through geometry control in accident scenarios
* Higher primary coolant volumetric heat capacity
* Visually transparent, low-pressure, chemically stable coolant

In addition to these cost lowering characteristics, the capacity of all MSRs to operate at a one atmosphere pressure offers a further and important cost lowering potential.

The ORNL Fast Spectrum report also noted characteristics of FMSRs that would lower electrical costs to customers, or increase utility revenue per unit of electricity generated. These include,

* No cladding-based burn up limits
* Higher operating temperature
* Flexible input fuel chemical form
* Flexible input fuel isotopic content

A number of FMSR characteristics that would raise capital costs include,

* No cladding as fission product barrier with a substitute fission product barrier
* Higher operating temperature
* Highly radioactive, fissile-bearing primary coolant
* Potential for safeguards concerns with separated material
* Material corrosion problems

In the case of materials corrosion, it should be noted that there is a low cost work around, if the designer is willing to accept a somewhat lower but still high by LWR operating temperature.

One MSR characteristics offer a mixed cost picture. This was:

* Continuous separation of fission products (and reduction of source term in accident scenarios)

Not only did continuous separation have potential to lower safety related manufacturing and construction costs, but it offered a potential for dramatically lowering regulatory costs. If gaseous and volatile fission products are removed from a reactor as they are produced by nuclear fission, then the motive for most aspects of nuclear regulation is disappears. Thus the cost of nuclear regulation can be lowered. In addition, if separated from the coolant salts, many fission products become salable, either immediately or after a laps of some time. Thus fission product separation can lead to a new revenue stream. Finally although fission product removal devices add to capital costs, their cost can be lowered if Molten Salt Reactors are mass-produced.

It should be noted that the capital cost raising and lowering picture is similar other forms of MSR, with factors such as coolant salt choice, core design including graphite use, and relative neutron speed (thermal, epithermal, and fast), effecting capital costs.

The Fast MSR offers a tool for managing the actinide content of nuclear waste. . In 1991, Uri Gat, and J. R. Engel of ORNL, and C. H. Dodds, of the University of Tennessee, proposed burning fissile fuel from dismantled nuclear weapons in LFTRs, as a means of nuclear deproliferation. That is the process of destroying the raw materials of nuclear weapons.

V. V. Ignatiev, S. A. Konakov, S. A. Subbotine, and R. Y. Zakirov of the Kurchatov Institute in Moscow, and K. Grebenkine proposed the use of Molten Salt Reactors as a means of disposing of nuclear waste. They noted that LFTRs had advantages over Liquid Metal reactors for nuclear waste disposal. The Russian research has lead to the development of the MOSART reactor design. The MOSART is a liquid salt fuel reactor concept intended to burn nuclear waste.
A similar proposal has come from Charles W. Forsberg of ORNL.

The integral Fast Reactor can perform a similar function. and while I have come to appreciate the IFR design, it still has safety problems that would not trouble a fast MSR design. In addition, fast reactors require very large start up charges, in comparison to MSR thermal thorium breeders. The large size of fast start up charges limits their scalability. Thus ten times as many LFTR can be started with the plutonium from nuclear waste, as IFRs or FMSRs. Fast reactors thus are an option for disposing of plutonium from nuclear waste. LFTRs can be started with Reactor grade plutonium (RGP), U-235 or U-233 if it is available. They can be started with a mixture of reactor fuels, or they can be started with all three. The current American stockpile of RGP is gig enough to start enough LFTRs to supply the entire American electrical demand and then some.

Some IFR advocates argue that high breeding ratio IFRs are rapidly scalable because they can produce a very large amount of nuclear fuel. But IFR design research and development has to date largely focused on IFRs capable of burning RGP with breeding ratios similar to those of thermal LFTR breeders. Higher IFR breeding ratios are undoubtedly possible, but they would require much R&D and would never be as safe as FMSRs. Thus RGP can be disposed of by fast reactors, but Lars Jorgensen has established that a fleet of thermal LFTRs can dispose of our entire stock of RGP in under 300 years. Thus if it is viewed as desirable to use the RGP found in "nuclear waste" to start thermal breeder LFTRs, it can be used to start hundreds of LFTRs. Since actinide disposal is the largest single problem associated with the so called nuclear waste issue, the thermal LFTR-RGP start option may well represent the best option for nuclear waste management.

At any rate ORNL FMSR report, offers further support for the contention that MSRs have the potential for lowering nuclear costs. The cost lowering features of the FMSR are all available in high scalable thermal spectrum LFTRs, as well as uranium fueled MSR designs. In addition small MSRs can be built in large numbers in factories. Factory produced small MSR/LFTR modules can be shipped by truck or by train to final assembly sites, or completely assembled in factories and shipped by barge. Not only can they be used to provide electrical power, but they can produce industrial heat, serve as the basis of combined heat and power systems, and even include bottom cycle desalinization. Thus the small MSR may prove to have not only a lower cost than conventional nuclear power plants, but superior versatility.

It is clear then that if breeder scalability and rapid manufacture is desirable, the thermal MSR/LFTR path holds significant advantages over the FMSR or IFR fast breeder approach.

ORNL's Energy Innovation Hub

Presiden't Obama's BLUEPRINT FOR A SECURE ENERGY FUTURE, released on March 30, includes mention of

As part of a broad effort to spur clean energy breakthroughs, Oak Ridge National Laboratory is leading an Energy Innovation Hub devoted to nuclear energy modeling and simulation. The Hub, which includes partners from universities, industry and other national labs, will use advanced capabilities of the world's most powerful computers to make significant leaps forward in nuclear reactor design and engineering.

The new Nuclear Energy Modeling and Simulation Energy Innovation Hub, is intended to be funded by $122 million over the next 5 years.

The Hub will use the capabilities of the world’s most powerful computers to work on nuclear reactor design and engineering.

A recent report stated

that 8 million processing hours will be directed to designing new and better reactors.

The Nuclear Energy Innovation Hub will allow engineers to create a simulation of a currently operating reactor that will act as a “virtual model” of that reactor. They will then use the “virtual model” to address important questions about reactor operations and safety. This will be used to address issues such as reactor power production increases and reactor life and license extensions.

In addition to ORNL a number of other universities, National Laboratories and other research institutions will collbirate in the project including:

• Electric Power Research Institute, Palo Alto, California
• Idaho National Lab, Idaho Falls, Idaho
• Los Alamos National Lab, Los Alamos, New Mexico
• Massachusetts Institute of Technology, Cambridge Massachusetts
• North Carolina State University, Raleigh, North Carolina
• Sandia National Lab, Albuquerque, New Mexico
• Tennessee Valley Authority, Knoxville, Tennessee
• University of Michigan, Ann Arbor, Michigan
• Westinghouse Electric Company, Pittsburgh, Pennsylvania

Energy Innovation Hub researchers will use the ORNL Super computer cluster The DoE intends to build a total of three Energy Innovation Hubs in order to research:

1. Fuels from Sunlight
2. Efficient Energy Building Systems Design
3. Modeling and Simulation for Nuclear Reactors.

The Hubs are intended to move the nation,

beyond our present overwhelming dependence on fossil fuels-and achieving truly significant reductions in greenhouse gas emissions on an urgent basis-represents a technological challenge of historic scale. Success will require major mobilization of our nation's basic and applied energy research capabilities, along with new investments in engineering and development to accelerate the deployment of revolutionary energy technologies in the marketplace. The developments of the atomic bomb under the Manhattan Project and of radar technology at the MIT Radiation Laboratory during World War II, as well as the invention of the transistor at Bell Laboratories in the 1950s, stand as evidence that exceptionally rapid technological breakthroughs are possible. These transformational breakthroughs came as a result of significant investments in highly motivated and focused scientific collaborations, combining basic and applied research, and aimed at overcoming a specific technological challenge.

The choice of ORNL as the lead Institution in the nuclear hub has very real significance for the national energy future. First, of the three hubs the Nuclear hub is likely to be the most important, because neither fuels from sunlight nor improved building efficiency are likely to do the heavy lifting required to provide the United States with future post carbon energy. ORNL has the largest suite of super computers of situated art any research institution in the world, but further, ORNL has both 60 year old tradition of Molten Salt Reactor research and development, and a growing interest in the research and development of Molten Salt cooled reactors.

Rediscovering Weinberg's Vision

I was in Oak Ridge to visit my father when Alvin Weinberg died. Immediately after Weinberg's death I looked at materials about him that were present on the Internet. I also had my memories of playing with Weinberg's son David when we were school boys. I recalled visiting the Weinberg home, and of David's mother Marge as well as Dr. Weinberg. The Internet stories were about the public side of Weinberg's life. I read an account of Weinberg's 80th birthday celebration at Oak Ridge National Laboratory in 1995, and a subsequent interview in which Weinberg talked about aspects of his career that were previously unknown including his firing.

Stories I looked at about Weinberg tied back to my father's ORNL career and my own year at ORNL. Mention was made in the materials I reviewed of the ORNL-NSF Environmental Studies project, at which I was employed as a sort of glorified intern for a year in 1970-1971. People I knew, who were involved in the Environmental studies project including project Directors David Rose from MIT, and later Presidential Science Advisor Jack Gibbons as well as Bill Fulkerson, later an ORNL associate director,were mentioned. Fulkerson described Weinberg as

Our Spiritual leader."

and said,

"He viewed national laboratories as tools for achieving social progress.

There is a tradition in Western thought, that goes back to Sir Francis Bacon, that views science as the primary tool for social Progress. Fiulkerson placed Weinberg squarely in that tradition. Among Weinberg's projects, was the use of nuclear energy to desalinate seawater and

make the deserts bloom.

The Weinberg story interlaced at significant points with my own life, among the significant projects which accounts of Weinberg mentioned, the Aircraft Nuclear Propulsion program, the Homogeneous Reactor Experiment, and the Molten Salt Reactor Experiment, all played roles in my father's ORNL, and he in particular, as I was to learn, made major contributions to Molten Salt Reactor Technology.

At the time of Weinberg's death I had begun a return to themes I had encountered during my ORNL days. Al Gore's movie An Inconvenient Truth had already opened a door to the past for me. During My ORNL days, Jerry Olsen had discussed briefed people working with the ORNL-NSF Project us on the CO2/Anthropogenic Global Warming problem. This was long before AGW became a political issue, and long before Republicans started reading Climate Audit and committing intellectual suicide. At that time it was perfectly possible to be a Republican and accept the mainstream science views on the greenhouse gas problem. Republican skepticism about AGW is not just wacky, it is tragic and pointless. What Republicans want is the continuation of economic freedom in the future. With a nuclear solution, they can protect the free market, while having an appropriate response to AGW.

When I worked at Oak Ridge National Laboratory (ORNL) in 1970-71, the idea of anthropogenic global warming was beginning to circulate. Alvin Weinberg had taken a long look at the future of humanity, and decided that for that long run to work, we had no choice but to use atomic power. There were two possible forms, Nuclear power from reactors, and thermonuclear power from Hydrogen fusion. T here was enough raw material available in the sea to last human energy needs a long time, but thermonuclear power posed daunting technological challenges.

Building advanced reactors was the option that appealed to Alvin Weinberg. And Weinberg, who was nothing, if not a forward thinker, had access to to the most forward thinking in the world about anthropogenic CO2 and global climate change, and idea that the upper reaches of the Atomic Energy Commission had begun to encounter during the 1950's. No less a figure than Willard Libby was interested in atmospheric CO2 as part of his radioactive carbon-14 research. Roger Revelle and Hans Suess were arguing the case for CO2 monitoring. The rational was simple and compelling. Scientists foresaw a need of "a clearer understanding of the probable climatic effects of the predicted great industrial production of carbon-dioxide over the next 50 years." Revelle tapped Charles Keeling to become the ultimate standard barrier of the project to monitor atmospheric CO2. By the 1960's awareness and concern about the long term implications of anthropogenic CO2 was spreading at the upper levels of the American Scientific community, and was beginning to enter into the voices of scientists who had influence over American policy.

During the late 1960's and early 1970's Weinberg's career and indeed the fate of ORN began to be effected by a high AEC official, The Director of Reactor Research Milton Shaw. Shaw was allied with the powerful Congressman Chet Holifield. It appears that neither Shaw or Holifield liked Weinberg. It is not clear if their animosity was at the root of their objection to Weinberg's ideas, but it is clear that they both felt that Weinberg had to go. There were clashes over the Molten Salt Reactor, and Reactor Safety. These were related issues. The Molton Salt Reactor, had a leg up in reactor safety, as compared to the then dominate light water reactor. Weinberg like many of his ORNL staff was acutely concerned about reactor safety issues. Weinbergs safety concerns directly conflicted with Holifield and Shaw. In 1973 Weinberg was fired as director of ORNL. But Weinberg was too big a voice to silence. In 1974 Weinberg published a major paper on the energy economy is the prestigious journal Science. In " Global Effects of Man's Production of Energy," Weinberg set out his case on the long term consequences of the human commitment to carbon based fuels. In 1975 during testimony to congress, Weinberg laid out his global warming concerns.

During his last years at ORNL Weinberg was very concerned about the Laboratory's future. also concerned about the future of ORNL. ORNL had been a reactor research center during the Weinberg years, and AEC reactor czar Milton Shaw had decided to shut down ORNL's reactor research establishment. Shaw decided that the AEC's biggest reactor research project, the Clinch River Breeder Reactor, was to be built within a couple of miles of ORNL, but without ORNL supervision. The result was a disaster.

Dixie Lee Ray claimed,

One of the notions he (Milton Shaw) had was his stated desire to destroy the Oak Ridge National Laboratory. I never really knew exactly why but I was equally determined that that fine American institution should live forever. At one time he (Milton Shaw) could have accomplished his goal, because he had Congressman Holifield on his side and both of them detested my old friend, Dr. Alvin Weinberg, who ran the Oak Ridge lab. To this day I don't understand the Holifield-Shaw dislike of Oak Ridge, but I had to believe it had no place in the Holifield nuclear empire.

Weinberg denied Ray's claim that Shaw wanted to destroy ORNL, but it is quite clear that Shaw damaged ORNL to a much greater extent than simply firing Weinberg. Weinberg has proposed during the late 1960's to turn ORNL into an Environmental Laboratory, but Holifield and probably Shaw was opposed to that. It is probably the case, even though Weinberg later denied it, that he was aware that the Laboratory needed a new mission if it were to survive as a scientific institution. Weinberg brought David Rose to ORNL to lead the rescue attempt. Rose was a visionary like Weinberg, and was perhaps along with Weinberg and my father one of the most outstanding people i knew while I was at ORNL. What i recall about Rose now was how approachable he was, and that was a rare quality among the many ORNL chiefs. Rose owned two old Aston-Martons and he maintained them as a hobby. His official title at ORNL was Director of Long Range Planning, and he was not entirely comfortable with the day by day supervision of the ORNL-NSF program. It is perhaps a mark of Rose charisma, that when he was replaced by Jack Gibbons, some people in the program including me felt disappointed. Gibbons was of course an outstanding scientist and science communicator, who was later Presidential Science Advisor to President Clinton.

I left Oak Ridge at the end of the summer of 1971, heading out for graduate school, and left the environmental and energy concerns I had found at ORNL behind me for 35 years. Then I heard a wakeup call from Al Gore's movie, "An Inconvenient Truth.' The death of Alvin Weinberg a few months later confronted me with the solution to the Climate problem that ORNL had to offer under Weinberg.

Following Weinberg's death I found that following his departure from the Laboratory, Alvin Weinberg had virtually assumed a prophetic mantel as he reviewed the issues forced on us by greenhouse gasses and the future of energy.

In a 1976 paper "Economic Implications of A US Nuclear Moratorium. 1985 to 2010," which Weinberg co-authored with Charles E. Whittle, Alan D. Poole, Edward L. Allen, William G. Pollard, Herbert G. MacPherson, Ned L. Treat, and Doan L. Phung, reveal to us exactly how accurate Weinbergs vision of the future was. In the paper Weinberg and his associates assessed the the economic and environmental consequences of moratorium on neuclear construction in the United States. He assumed that no new reactors would be ordered after 1980, but that reactor construction would continue till about 1985. He then looked at the consequences to allow continued operation of reactors on line by 1985. Weinberg tried to think out the implications of the cesation of new reactor construction.

Weinberg understood that if reactor construction ceased, power companies would construct more coal fired power plants to meet consumer demand for electricity. Weinberg assumed that consumer demand would be driven by two factors population growth, and economic growth. He also assumed that technological changes would increase the efficiency of electrical use, but that these efficiencies would not offset the increase in demand.

Weinberg saw

"four levels of environmental tradeoffs as a result of shifting the additional fuel requirements from nuclear to coal after 1985."

The first level of effect was what he called global. There were two components:

(1) Proliferation: Countries wishing to rely primarily on the nuclear option can do so whether or not the United States abandons nuclear power. Thus, a domestic moratorium on nuclear energy would have little effect on proliferation unless the rest of the world abandoned nuclear power.

(2) CO,: Should 20 percent of the world’s fossil fuel be burned, the CO(2), concentration might double; this could lead to unacceptable changes in the world’s climate. A U.S. moratorium per se would have little effect on this possibility; however, loss of the nuclear option through much of the world,’which is a conceivable consequence of a U.S. moratorium, might make it more difficult to respond quickly to a perceived danger from higher CO(2), levels in the atmosphere.

Weinberg's observations on CO2 were extrordinary:

The ultimate constraint on the burning of fossil fuel may be the climatic impact from atmospheric CO(2) buildup. This, of course, is a global problem; what the United States does during the next 30-50 years is likely to contribute little to total global atmospheric levels. Nevertheless, increasing reliance on fossil fuel by such a large consumer as the United States poses a prospect of severe climatic shifts that cannot, in principle, be dismissed. The extent to which a nuclear moratorium would aggravate the buildup of CO(2), must therefore be examined.

Carbon dioxide in the atmosphere affects the thermal radiative balance of the planet and through this balance the global climate. On the basis of the best atmospheric models now available, a doubling of the atmospheric CO(2), would result in a global average surface temperature increase of 1.5-2.4"C, with greater increases in the high latitudes. Although models of the type used in these studies predict present global climate surprisingly well, a number of significant variables are not included. Consequently, the results must be regarded as preliminary until additional information and more reliable climatic feedback mechanisms can be properly included.

During the past hundred years, the annual global production of CO(2), by burning fossil fuels has grown nearly fiftyfold. It now stands at 18 x lo9 tons, which is about one-tenth the amount accounted for by the annual net primary fixation of carbon by terrestrial plants. This production appears to have caused an increase in the concentration of CO(2), in the atmmphere. Since 1958 observers at the Mauna Loa Observatory in Hawaii have monitored atmospheric CO, content, and the 1975 measurements show an average CO(2), concentration of 330 ppm (in the latter part of the nineteenth century it was 290-295 ppm). The measurements show annual increases for each year, averaging about 0.7 ppm during the late 1950s and early 1960s and up to 1 .O ppm or more in recent years.

The cumulative production of C02 since the end of 1957 and the observed increase in CO, are plotted in Figure 8. The upper set of points indicates the increase in concentration of CO, in the atmosphere that would have occurred if all CO, produced from fossil fuels and cement since 1957 remained airborne. The lower set of points represents the observed increase in atmospheric CO, concentration at the Mauna Loa Observatory.

Weinberg added:

Almost any reasonable scenario for future global energy demand yields continued increases in atmospheric C02, but the resulting concentrations do not appear to reach levels that will cause severe climate alterations before 2000. However, little complacency should be derived from this, since continued energy demands during the first few decades of the next century will push atmospheric C02 concentrations to levels which warrant serious concern, even for the low
energy growth case. The inertial effect in energy supply systems makes it clear that decisions made now on the nuclear/nonnuclear issue will have an impact reaching many years into the future.

He observed "that the time when atmospheric CO, concentration will become crucial is early in the twenty-first century." He expected "an increase of 62-73 ppm over the 1958 value of 315 ppm by 2000. " Then he added, "atmospheric concentration of 375-390 ppm may well be a threshold range at which climate change from C02 effects will be separable from natural climate
fluctuations. "An increase of 150-225 ppm by 2025 (concentration of 465-540 ppm) should certainly result in recognizable climate change if such changes are ever to occur. The consequences of an increase of this magnitude in atmospheric C02 make it prudent to proceed cautiously in the large-scale use of fossil fuels."

In both nuclear proliferation and CO2/global climate change Weinberg was clearly correct. In 1974 India exploded its first Atomic bomb without possessing American reactors. Other nations followed in developing nuclear weapons programs without relying on American designed and built power reactors. South Africa which actually assembled 6 nuclear weapons during the 1980's. Pakistan built nuclear weapons using its own resources from the 1980's onward. Pakistan is believed to have stolen technology from the West, and also received some technological help from China. North Korea was able to construct nuclear weapons with Pakistani help. Iraq's nuclear weapons programs were blocked by Israeli military action in the 1980's, and by international pressure and military actions since the 1990's. Iran which received Pakistani help in developing a weapons program, but appears to have stopped the program for technical reasons as well as international pressure. Libya also received Pakistani help on developing a nuclear weapons program, but appears to have dismantled that development a few years ago, after an agreement with the United States. Israel acquired nuclear weapon making capacity during the 1960's with some French assistance.

Weinberg was also correct about the implications of an American reactor construction moratorium for CO2 emissions. The world wide demands for energy has increased rapidly, and as of January 2011, much of that demand has been filled by coal burning power plants. Despite the 1976 prophecy of Amory Lovins, that coal use would be in decline by 2011, Coal use for energy and its threat to the climate is still very much with us. In a discussion of Lovins vision or perhaps more accurately lack of vision of the future. Lovins had foreseen a coal burning bridge to a low energy, energy efficient future. Weinberg asked,

Can we really ignore CO2 during the coal burning fission free bridge?

Weinberg commented on the title of Lovins book, The Non-Nuclear Futures,

Despite its title, the book is not concerned with non-nuclear futures. The reader of a book so named is entitled to get from the authors a reasoned description of a feasible non-nuclear future. The authors excuse this omission with the assertion (p159), 'To show that a policy is mistaken does not oblige the analyst to have an alternative policy.' But this is inadequate. This is not dealing with a hypothetical issue, but a real one. It is not enough to point out the deficiencies of nuclear energy; one must deal with the situation that would arise if Lovins and price were successful in their onslaught: should the society indeed turn away from nuclear energy, what then?

What then Weinberg argued, against Lovins, was a loss of freedom. My own assessment is that Weinberg was correct, and that Weinberg not Lovins and the anti-nuclear environmentalists was the true progressive and the true champion of human freedom.

David LeBlanc at ORNL, May 2010

Update: See this recent interview with David Le Blanc.

I Speak for the Dead

One of my favorite television shows has been Di Vinci's Inquest, a Canadian series from a few years ago. Di Vinci, a coroner has a line, "I speak for the Dead." In "Nuclear Green, I, of course, speak for myself, but beyond that, I speak for the dead as well. To explain what I mean, I would like to briefly refer to two bloggers who are very much living, Barry Brook and Kirk Sorenson. In a recent post, Barry spoke of what might be called his Damascus Road revelation about nuclear power. Barry in the not very distant past was a Australian climate scientist who had started to blog, and who had as of yet not thought through the energy issues. Barry wrote that in an early post he had extoold Australia;s renewable resources. Barry recently wrote,

my focus at this point was pointedly directed at carbon emissions reduction (clean energy was just a means to an end), and it was obvious to me that the logical path to achieve this was renewable sources such as solar and wind power. I was coming at this issue from a genuine concern for eliminating carbon-based energy, and was overwhelmed by a sense of frustration, because I couldn’t understand why the ‘clean energy revolution’ wasn’t happening. . . Indeed, I hadn’t given much thought to nuclear power at this point, not because I was ever ideologically ’anti-nuclear’ — I had simply accepted the ‘peak uranium’ argument and not thought much more about it, as this comment I made back in Dec 2008 indicates.

Then, reality bit me, and it hurt. I remember I was sent an early version ofTrainer’s thesis, and against all reason (’what nonsense is this?‘ I recall first thinking), I read the damned thing. Somewhat crestfallen, yet also morbidly fascinated, I followed up, reading ‘The Solar Fraud‘ (the only other book on this topic of renewable limits, according to Trainer’s piece) and then a bookshelf worth of other tomes on this general topic, including ‘Sustainable Energy: Without the Hot Air‘ and ‘Prescription for the Planet‘ (kicking off my nuclear education in earnest), followed by various technical analyses, IPCC WG III, blogs, etc. My first post on this blog on nuclear power was on 28 Nov 2008, 3 months after it has been launched. My transformation of thought had begun in earnest, and was reinforced by the work of people such as Peter Lang.

Kirk Sorensen responded to Barry's post:

I had a similar conversion story…I was once a hard-core wind and solar guy, spending lots of time thinking about how to cover deserts in solar concentrators and build windmills. I couldn’t figure out why everyone didn’t want this, but a couple of summers living in the Mojave and seeing the remnants of past solar projects and the half-broken windmills of the Tehachapi Pass began to dampen my enthusiasm.nNuclear didn’t seem particularly compelling to me. I had a lot of mistaken ideas, but there was still a lot of stuff about LWRs that I had right and left me underwhelmed. My conversion began when I started reading a book called “Fluid Fueled Reactors” and around the same time read an article written by Rod Adams on the subject of thorium…

Barry and Kirk can only testify to the living. They bare witness to themselves, they tell us what they experienced, how they came to certain views. I can speak for the dead, because I was a witness to their lives.

The dead include the Nobel Prize winning scientist/engineer Eugene Wigner who I, along with other ORNL supernumeraries, meet one summer afternoon in 1971. I did not fully appreciate who Wigner was then, but a long time later, as I began to understand the history of nuclear technology, I began to appreciate Wigner's towering genius.

The dead include Alvin Weinberg whose death triggered my recognition that Weinberg's generation of nuclear scientists had a lot to say to the living. Weinberg was far more than a reactor designer and science administrator, he was also a deep thinker who had a great deal to say about the role of energy and science in society. Weinberg offered a clear vision of the future, that has proven far more accurate than Amory Lovins has.

I speak for my father whose numerous contributions to nuclear science were almost unknown before I began to discover them in his papers. My father's vision of the future was clear, and pointed unmistakably to a future in which nuclear energy was to be a safe, clean and reliable source of energy for our future society.

I speak for many ORNL scientist of my father's generation, Ed Bettis, George W. Parker, Bob Moore, Raymond C. Briant, Warren Grimes, and numerous others, who worked to make safe, clean and reliable nuclear energy available the people of earth.

I first realized that the dead needed a voice when Alvin Weinberg died in October 2006. Alvin had been the father of a childhood friend, David Weinberg, and I had had a distant acquaintance with Alvin from my childhood onward. In reviewing past stories about Weinberg in the ORNL Review, I discovered the astonishing fact that Weinberg had been fired as ORNL director in a spat with AEC leadership over Weinberg's insistence that continued nuclear safety research was important. It was clear that Ralph Nader had known both about Weinberg's firing and the circumstances around it, but Nader, who professed to be concerned about nuclear safety chose to say nothing on Weinberg's behalf. Weinberg's vision of the future has proven far more accurate than that of Amory Lovins, who he befriended and sparred with over their contrasting visions of the energy future. Important parts of the Weinberg legacy is accessible on the Internet, much through The Information Bridge.

In 2007, for the first time I thought seriously about carbon mitigation. It did not take me long to find a solution. Part of my solution, scalability energy through reliance on mass produced small reactors, was very much a part of the spirit of our time. But the memory of voices from the past influancec my designation of the Thorium Molten Salt Reactor, the LFTR as the technology of the future, as the energy Black Swan. Fortunately my father was still alive then, and I had the unique opportunity to talk with him as I read his papers. I want to briefly mention Richard "Dick" Smyser, the long time editor and publisher of the Oak Ridger. I mention Smyser because he was the faithful scribe who reported the visions, wishes and aspereations as of Oak Ridge scientists as they emerged.at ORNL. It was through Smyser's reporting that I learned much about the visions of a high energy nuclear future pioneered by Alvin Weinberg and the ORNL staff. during my childhood and early adult years.

In a way, what I say now about nuclear power and particularly Molten Salt Reactor/LFTR technology is said for those who no longer speak for themselves. I speak for the dead. I bear witness to their voices. I learned of Anthropogenic Global Warming at Oak Ridge National Laboratory in the spring of 1971. I had no doubt from the first moment that nuclear power would offer a superior solution to the problem. I watched for decades after 1971, as so called renewables advocates such as Amory Lovins openly advocated the use of carbon emitting coal, oil and natural gas technology in preference to nuclear generated electricity.

Dick Smyser told the Oak Ridge Story, and Environmental concerns were a part of it

I found two unpublished posts related to Thomas Pigford today in a search of my old posts. I thought these were to good to leave under raps

One of the things that happened to me while growing up in Oak Ridge, is that I managed to assimulate the viewpoint of the atomic pioneers. I had no idea at the time of the importance of Eugene Wigner to the shaping of the ORNL/Oak Ridge mentality. In fact Wigner was often in the background and his thinking was communicated to Oak Ridge in ways we little suspected. Dick Smyser had a lot to do with the communications of the ORNL View to the community. Smyser was the editor and later the publisher of the Oak Ridger. Smyser was more than a jurnalist. His Brother-in-Law, Thomas H. Pigford, who was a former ORNL engineer, a Professor of Nuclear Engineering at the University of California, Berkele, and the only nuclear scientist to serve on the Three Mile Island Commission. The Pigford connection gave Smyser an added in with the ORNL staff, On addition Smyser had an "in house" expert he could turn to for insight, when he did not understand something. As a consequence Smyser not only kept Oak Ridgers well informed anout developments at the lab, but he helped to make Oak Ridge a uniquely nuclear literate community, I have little doubt that Weinberg sharred his thoughts with Smyser on more than one occasion, and Smyser had a social relationship with many ORNL scientists, and would have at leasst meet Wigner and been aware of his importance in creating in Oak Ridge a high level of nuclear literacy that extended beyond the scientific community. I am sure that I picked up terms like neutron economy and breeder blanket from the Oak Ridger, although I did not fully understand what they meant until I began to look closely ate the MSR in 2007. The MSR came well before the current energy crisis, but it was understood in Oak Ridge that the thorium fuel cycle MSR had the potential to provide all of the nation's energy in the future. By the 1960's the vision of a high tec future that would benefit not only the United States, but the world's poorest people, had taken hold in Oak Ridge, and the Oak Ridger reported on it.

Pigford was an expert on both the Uranium andthe thorium fuel cycle, and no doubt Dick Smyser learned something about those subjects from his brother-in-law.

So I grew up nuclear literate and exposed to the world view that lay behind the most daring scientific projects of Oak Ridge scientists. In addition Oak Ridge carried with it the Manhatten Project legacy. The story of K-25 particularly informed the Oak Ridge view of the world. K-25 was huge. It had been the world's largest building under one roof when it was completed during World War II. The isotope separation process used at K-25 was not perfected until construction was well underway. That sort of experience engenders a measure of self confidence. Oak Ridgers had considerable confidence in the power of their technology. They knew that a business as unusual sometimes needed to be set aside and that a great deal could be accomplished by people who were hard working and intelligent. The first atomic bomb that was dropped on Japan used uranium that was processed at Oak Ridge. From 8 tons of Uranium K-25 and Y-12 produced 64 kg of U-235. When the Little Boy bomb went critical, a little more than 1% of the U-235 in the bomb fissioned and about 0.6 g of that mass was transformed into energy. That bomb exploded with the energy equivalent of 20,000 tons of TNT. Most energy writers are unaware of the enormous amount of energy that can be extracted from tiny amounts of matter.

Oak Ridge Scientists conceived of the The Light Water Reactor and made major contributions towards its development, but Oak Ridge scientists knew that the LWR is a very inefficient means of turning matter into energy in a nuclear process. The Light Water Reactir core has to be far larger than a Molten Salt Reactor core. Small cores requite less material and labor to build. They are not necessicarily less safe.

The Oak Ridge vision was in no small measure formed by the natural setting of the city. Oak Ridge has a beautiful setting, and few places where the human species has found itself living can rivaled East Tennessee for natural beauty. Between 1942 and the present many people have lived in Oak Ridge for a short time, but those who tendede to stay, were people who enjoyed the natural setting. As a result Oak Ridge was a city of unusual environmental awareness.

ORNL uses the beauty of the Oak Ridge area as a selling point for employee recruitment.

It was inevitable that ORNL was to become a center of environmental research and from the 1970's onward took the scientific lead in pointing to potential environmental problems caused by CO2 emissions. Oak Ridge scientist understood that burning fossil fuels represented a long term threat to humanity and believed that nuclear power could make an important contribution to the successful prevention of that threat.

Phoenix Rising

I attended David LeBlanc's lecture at ORNL yesterday (May 18, 2010).

Jess Gehin, our host, took the opportunity to do a set of show-and-tell presentations about molten-salt-related programs at ORNL. It is safe to say, from what I saw yesterday, that the phoenix is rising at ORNL.

David's talk was exciting. David has been in contact with retired ORNL MSR researcher Dick Engel. Dick participated in the ORNL 1980 fling at getting backing for Molten Salt Reactor development, the DMSR. (For documentation of the DMSR concept, see here, here, here and here.) David notes in his Mechanical Engineering article,

The “D” stands for “denatured”—the uranium in the reactor contains too much U-238 to be useful in weapons. The concept also dispenses with processing the salt to remove fission products; the same salt is used throughout the 30-year life of the reactor with small amounts of low enriched uranium added each year to keep the fissile material constant. The amount of uranium fuel needed—about 35 metric tons per GWe year—is only one-sixth of what is used by a pressurized water reactor. . . .

The amount of fissile material needed to start new reactors is also very important, especially in terms of a rapid fleet expansion. The 1 GWe DMSR was designed for 3.5 metric tons of U-235 (in easy-to-obtain low-enriched uranium) which can be lowered if uranium costs go up. A new PWR, by contrast, needs about 5 metric tons, whereas a sodium-cooled fast breeder such as the PRISM design requires as much as 18 tons of either U-235 or spent fuel plutonium. Any liquid fluoride reactor can be started on plutonium as well, but this turns out to be an expensive option, since removing plutonium from spent fuel costs around $100,000 per kilogram.

Reviewing the DMSR from a 2010 perspective, LeBlanc finds many advantages.

The DMSR features a larger, lower power density graphite core than other MSR breeder concepts. So while the graphite would last a full 30 years, the DMSR would still be only a fraction of the size of gas-cooled graphite reactors and would not require a pressure vessel. In fact, the simple thin-walled DMSR containment vessel would be wider but much shorter than those of PWRs and BWRs. The construction of the reactor containment building offers savings as it does not need the huge volume and ability to deal with steam pressure buildup needed for LWRs or CANDU reactors.

The overall thermal efficiency of the plant would be quite high. With a salt outlet of 700 °C and using the latest ultra-supercritical steam cycles or gas Brayton cycles, efficiencies close to 50 percent would be possible.

While up-to-date cost estimates for a molten salt reactor are not available, it is quite simple to see the potential overall advantages. The DMSR needs no capital and O&M costs for fuel processing, and the superior nature of the salts as coolants results in far smaller heat exchangers and pumps. Building and fabrication costs should be lower than conventional nuclear plants, since the design doesn’t put the same sort of stresses on the system.

Among the advantages LeBlanc points out, the potential to lower nuclear costs is the most conspicuous.

It is not unreasonable, then, to assume that capital costs could be 25 to 50 percent less for a simple DMSR converter design than for modern light water reactors. Compared to fast breeders such as the integral fast reactor, which rarely try to claim low capital costs, the DMSR should be even better.

In his ORNL talk, LeBlanc noted the possibility of simply eliminating a Thorium blanket for the DMSR entirely, and running the DMSR as a pure uranium-fuel cycle reactor. While the Uranium fuel cycle DMSR would offer less sustainable technology than the LFTR, it would be a very strong competitor for the current generation of Light Water Reactors. It would offer a very high level of safety, proliferation resistance and nuclear waste control, at a lower cost that current light-water reactor technology. Actinides, the big problem in nuclear waste, could be separated from reactors salts, either periodically or when the reactor is decommissioned. The recovered actinides can be returned to the core of a DMSR where they will be burned as nuclear fuel. Other fission products will essentially disappear after 300 years, if reactor managers chose to treat them as waste, but this is unlikely. Fission products present in "spent nuclear fuel" represent a potential source of valuable materials and noble gases, and the DMSR concept opens the door for the recovery of these minerals.

LeBlanc concluded his Mechanical Engineering essay by declaring,

Molten salt or liquid fluoride reactors will also take a large effort, but every indication points to a power reactor that will excel in cost, safety, long-term waste reduction, resource utilization, and proliferation resistance. As we move deeper into a century that portends financial instability, political uncertainty, environmental catastrophe, and resource depletion, this technology is too valuable to once again place back on the shelf.

Nuclear Green concurs with this view. The DMSR represents a technology that is doable in the year 2010. The technology required to build it exists now, thus developers would not be saddled with huge R&D costs, and and the technological uncertainties that would confront LFTR development. The DMSR would represent a transition, between the traditional solid fuel reactors, and the sustainable LFTR technology. The Phoenix is beginning to rise from its ashes.

Disastrous Stewardship 2: The Weinberg firing

My historical research has been driven by a desire to understand the past. Not an abstract past, but events which I in some way witnessed. Much of the past is beyond knowing, thus some and perhaps many of the questions that I ask are beyond knowing as well. The central problems of my historical studies concern the scientific careers of two men, my father C.J. Barton, and Alvin Weinberg. My interest in my father's career undoubtedly is linked to some of my personal concerns that streatch back to my childhood. Researching my father's career is a way to maintain a link to someone whom I loved even though he is no longer with us.

My interest in Alvin Weinberg career also is linked to my past. Weinberg's son David was a childhood friend, and I was fond of David and of David's mother Marge Weinberg. My central focus on Weinberg has been on his firing as ORNL Director in 1972. Who is it that this prominent scientist, this brilliant reactor designer who held the original patent on the predominant form of 20th century reactor, this science advisor to presidents, this able science administrator, this serious thinker about the role of science in contemporary society, was fired from his position as director of Oak Ridge National Laboratory?

It is clear that a clique centering around Congressman Chet Holifield, and including AEC Commissioner James T. Ramsey, AEC reactor research director Milton Shaw, and Admiral Hyman Rickover exercised great control over the United States Atomic Energy Commission during the 1960's and early 1970's. Arguably Holifield used his status as a member of the Joint Congressional Committee on Atomic Energy to exercise great and even unconstitutional control over the AEC.

The relationship between members of the Holifield clique and AEC Chairman Glen Seaborg should receive further clarification, but it would seem that Seaborg, although he does not seem to have opposed the Holifield clique, was not a member. Seaborg's goals were apparently consistent with those of the Hoifield clique, and Shaw appears to received his marching orders on fast breeder reactors from Seaborg, without a Holifield veto.

Weinberg discussed his firing:

I found myself increasingly at odds with the reactor division of the AEC.

Weinberg explained the background of the problem, The Nixon administration had made the LMFBR a center piece of the American nuclear program. Shaw was committed to the Nixon Administration goal, andShaw was a ruthless administrator who permitted no opposition to his goals. Shaw did not trust Weinberg or the conclusions of ORNL scientists, Weinberg was on the wrong side of the dispute about reactor safety, and Shaw and his patron Chet Hollifield appeared to have believed that Weinberg was fishing for funding for unneeded research. Holifield personally announced to Weinberg

I think it is time you leave nuclear energy.

Weinberg clearly believes that Shaw and AEC Commissioner James T. Ramsey play roles in the decision.

Weinberg does not mention either Rickover or Glen Seaborg in his accounts of his firing. if Rickover and or Seaborg were involved in the Weinberg firing it would have been from behind the scenes. But it was at the very least the case that neither Rickover nor Seaborg broke ranks to defend Weinberg. At best, both acquiesced by silence to Weinberg's firing. Both should have known better and acted better.

(I should note however that I have revised my view of Rickover's role in the Weinberg firing. Originally, I viewed Rickover as Milton Shaw's primary patron in the AEC. But Shaw appears to have faithfully carried out Holifield's wishes, and Weinberg's firing was clearly in accord with Holifield's wish. In the absence of stronger evidence, my earlier charge against Rickover must be regarded as not proven, although i should not be considered as offering a definitive word on the issue. More research would be required.)

Weinberg's firing must be considered a product of the Holifield - Shaw - Ramsey relationship. That relationship must now be seen as having damaged the prospects of nuclear energy in the United States. It also lead to the premature termination of nuclear research, and the exclusion of a very promising line of reactor development that could potentially solved the problems of nuclear energy that critics found so objectionable.

The Weinberg firing was not an insignificant event as Weinberg himself understood. It marked the end of "the first nuclear era," as Weinberg himself well understood. It marked the end of the promise of nuclear power foreseen by the visionaries of the Manhattan Project's New Piles Committee in 1944-45. ORNL under Weinberg had had been the primary keeper of the New Piles Committee vision. Holifield, Shaw and Ramsey attempted to destroy the vision, and would have destroyed ORNL if necessary to achieve that goal. They did destroy ORNL's capacity to cary out the vision, but they did not destroy the memory of the vision, and the memory of what ORNL under Weinberg was able to accomplish. The memory is still with us. The phoenix arrises from the ashes.

David LeBlanc: ORNL and Too Good to Leave on the Shelf

David LeBlanc of the Physics department of Carleton University, Ottawa, Canada and the Ottawa Valley Research Associates, Ltd., is a highly regarded participant in Energy from Thorium discussions and a reactor scientist of considerable note. David is notable because of a significant accomplishment. He has simplified the reactor core to a point beyond which further simplifications are likely to prove impossible. David's reactor core is nothing more than two metal shells, one inside the other. A fluid fuel carrier/moderator/coolant flow into the inner shell, and then out again. A fluid containing fertile thorium flows in a and out the second, outer shell. That is it. The entire core structure is composed of two sheets of shaped metal, one surrounding the other, with openings through which a very hot salt fluid is designed to flow. In the inner chamber, fissionable material that is chemically bonded to the carrier salt becomes critical.

No control rods are control rods are required to control David's reactor, because the inherent properties of the carrier/coolant salt automatically provide feedback that can control reactivity within the core and even shut the reactor down completely.

David is scheduled to give a talk titled, Molten Salt Reactors: An Exploration of Design Space

on May 18, at ORNL.

The abstract David's talk states:

This talk will first review past and current molten salt reactor design principles covering the main development period at Oak Ridge National Laboratory (ORNL) as well as more recent work such as the Thorium Molten Salt Reactor of France (now called the Molten Salt Fast Reactor) and the FUJI concepts of Japan. Two new proposed design routes will then be presented. First a novel but simple core geometry modification to solve the issues that led to the abandonment of ORNL's Two Fluid efforts of the mid-1960's. Two Fluid designs have separate salts to carry the fertile thorium and fissile 233U and which benefit from greatly simplifying fission product removal but previously called for unworkable core architecture. Secondly, the untapped potential of ORNL's late 1970's work on denatured converter reactors termed DMSRs and proposed improvements will be presented. This more conservative route will be shown to also have attractive resource sustainability and long-lived waste reduction while requiring the minimum of development work and maximizing proliferation resistance.

In addition to his pending ORNL talk, David is the author of a new article in the May 2010 issue of Mechanical Engineering, "Too Good to Leave on the Shelf.". The Article offers a brief history of the ORNL Molten Salt adventure, some fascinating pictures,

Alvin Weinberg and the ORNL MSRE at 6000 hours of operation.

and David's own ingenious solution to a vexing problem that frustrated ORNL researchers in the 1960's. David also discusses the highly proliferation resistant DMSR, which has recently occupied his interest. He states

The amount of fissile material needed to start new reactors is also very important, especially in terms of a rapid fleet expansion. The 1 GWe DMSR was designed for 3.5 metric tons of U-235 (in easy-to-obtain low-enriched uranium) which can be lowered if uranium costs go up. A new PWR, by contrast, needs about 5 metric tons, whereas a sodium-cooled fast breeder such as the PRISM design requires as much as 18 tons of either U-235 or spent fuel plutonium. Any liquid fluoride reactor can be started on plutonium as well, but this turns out to be an expensive option, since removing plutonium from spent fuel costs around $100,000 per kilogram.

The DMSR features a larger, lower power density graphite core than other MSR breeder concepts. So while the graphite would last a full 30 years, the DMSR would still be only a fraction of the size of gas-cooled graphite reactors and would not require a pressure vessel. In fact, the simple thin-walled DMSR containment vessel would be wider but much shorter than those of PWRs and BWRs. The construction of the reactor containment building offers savings as it does not need the huge volume and ability to deal with steam pressure buildup needed for LWRs or CANDU reactors.

A Primer on Nuclear Safety: 2.5 Defense in Depth

A Primer on Nuclear Safety:
2.5 Defense in Depth
The Pebble Bed Reactor Option

During the late 1940's research began in Oak Ridge on safe reactor designs.
Farrington Daniels was a pioneering advocate of the practical use of solar energy. Daniels had been, during World War II, assistant director of the University of Chicago Metallurgical Laboratory chemistry devision. The Metallurgical Laboratory was the great incubator of reactor designs. Daniels had done research on the concept of using a furnace filled with small balls or pebbles to fix nitrogen from air. Daniels developed the idea of building a reactor along somewhat similar lines to the pebble furnace, and in 1945 he applied for a patent for it.

There was enough interest in Daniels pile, that in 1946 design work intended to facilitate its development began in Oak Ridge at the Clinton Laboratory, later Oak Ridge National Laboratory. Oak Ridge was the primary inheritor of the Metallurgical Laboratory's tradition of reactor innovation. That pebble Bed research was set aside when the researchers were reassigned to help develop the light water reactor for the Navy. By early 1950's ORNL research had focused on an even more radically innovative reactor concept, the Molten Salt Reactor, thus the Daniels' pile, as it was called in Oak Ridge, was shelved.

Daniels Idea was embed uranium in small graphite balls or pebbles. The pebbles would be placed inside a chamber, and cooled with helium. The graphite would serve as a moderator, an given the presence of enough uranium inside the balls of moderating graphite, a chain reaction would commence.

After the death of Daniels project in Oak Ridge, the pebble bed idea lay dormant for a few years. then in 1956 a German physicist Rudolf Schulten picked it up and began to develop it. The British were developing gas cooled, graphite moderated reactors the time, and gas cooled reactors offered some attractive advantages over the rapidly emerging American Light Water Reactor. Schulten believed that a pebble bed reactor could be built that would be inexpensive to build and operate, and would be far safer than the American Light Water Reactor. In addition the Pebble Bed Reactor would operate at a far higher temperature, and thus would have greater thermal efficiency than the Light Water Reactor.

The Pebble Bed Reactor looked like a good match to the thorium fuel cycle and there were real concerns in the 1950's and 60's about how long the supply of uranium would last. So the original concept was to make the PBR a thorium breeder. This intention was defeated by the proliferation resistant nature of the PBR's pebbles.

The first German Pebble Bed Reactor, the AVR was conceived to be highly safe. The Pebbles themselves are a major source of PBR defense in depth. Each pebble contains thousands of tiny Uranium dioxide particles. The Uranium dioxide particles are surrounded by multiple layers of material including a carbon inner buffer, followed by an inner layer of pyrolytic carbon, a layer of ceramic silicon carbide, followed by a second outer layer of pyrolytic carbon. Thus each fuel particle contains a five layered defense in depth. In addition the particles were designed to withstand the stress, and high tempreture expected to be encountered in the PBR.

The German Pebble Bed Reactors had one remarkable feature that is repeated in reactor developed from the PBR concept. The pebbles were blown into the reaction chamber by helium gas, and suspended within the reaction chamber by the gas flow. Thus the pebbles had to be designed to withstand the mechanical stress of constantly bumping into each other in the reactor's chamber, as well as the high temperature encountered in the reactor core. The fuel particles were believed to be capable of withstanding the sort possible accident possible with a PBR, hence even without the other PBR fuel safety measures, they offered a high level of inherent safety. The Triso particles were are in turn embedded in graphite pebbles.

The Germens built two pebble bed reactors. The AVR was a successful experimental prototype operated between 11966 and 1988. The THTR-300 was a developmental reactor intended to prepare the way for commercial deployment of PBRs. During its brief operating history between 1983 and 1989 the THTR-300 suffered from the sort of teethings problems common with new technologies. It was by no means a failure, but at the time of the project shutdown there were clearly developmental issues remaining to be addressed. The THTR was originally intended to operate as a thorium fuel cycle reactor, but reprocessing the nuclear fuel proved to be complex and expensive, and the thorium cycle was dropped for a conventional once through Enriched uranium approach. The THTR used no less than 670,000 6cm fuel pebbles. The German Pebble Bed reactor research program was shut down in 1988-89 as a political consequence the Chernobyl accident. At The time of the project shut down, design work was proceeding on the HTR-500, which was intended to be the first commercial PBR.

The PBR was regarded as highly safe. It could be shutdown with cno core cooling without core damage. During AVR testing the reactor was actually brought to shut down with the cooling system turned off. No core damage occurred. This was a remarkable performance. Shutting down a LWR without cooling will lead inevitably to core meltdown due to the heat generated by the radioactive decay of fission products.

The safety features of the PBR include:

- The use of Graphite in the core structure and fuel pebbles.

- The fife layered defense in depth of each fuel particle contained within the fuel pebble

- The SiC coating layer on fuel particles intended to insures the retention of fission products

- Low radiation levels in the environment of the reactor - opperators received only 20% of the radiation experienced by LWR operators

- The use of Helium as a coolant

- Passive removal of decay heat

- Maximum core heating remained below the level that would damage core and fuel structures

- The use of very strong prestressed concrete in the reactor vessel

- The capacity of the outer reactor structure to withstand the impact of an aircraft

The NRC notes:

Because the PBMR is continuously refueled, the excess reactivity can be kept low. Also, the design has a more negative fuel temperature coefficient than LWRs, as the Doppler feedback is greater for the less-thermal neutron spectrum associated with a graphite moderator.* These features reduce the risk of reactivity accidents for most scenarios (but increases the risk for accidents involving core overcooling).

A major component of the PBMR safety basis is a low power density (an order of magnitude below that of an LWR) and large thermal capacity (as a result of the large mass of graphite in the core), together with the high-temperature resistance of the fuel. The maximum power rating of each module (265 MWth) and the high surface-to-volume ratio of the core were chosen so that in the event of a loss of coolant from the primary system, adequate cooling would be provided without the need for forced convection. PBMR designers claim that in the event of a total loss of primary coolant and no operator intervention, the core heatup rate would be slow and the maximum fuel temperature would not exceed 1600 C. Thus the design does not include conventional emergency core cooling systems, which are required for LWRs to provide emergency water sources in the event of a loss-of-coolant accident.

The German PBR project was subsequently regarded as an outstanding success. Not only wree over all project goals meet till the time of shut down but the expectation existed that the technology could be developed into a revolutionary commercial reactor that could be built at a lower cost than conventional light water reactors, yet would operate with at a higher temperature which in turn would lead to greater thermal efficiency. The PBR design has a high level of inherently safe.

Following the shut down the potential of the PBRM was recognized by commercial interests in South Africa, and by the Chinese. Projects to develop PBR technology for electrical generation and process heat have been undertaken in both countries. Both programs expect to build PBRs in factories with serial production beginning by 2020. Between 2020 and 2030 hundreds of PBRs may be built in Chinese and South African factories.

So far I have pointed to the numerous safety advantages of the PBR. However the NRC has questioned the safety adequacy of current PBR designs.

PBMR advocates are so confident in the safety of the reactor (some even call it "meltdown-proof") that they have proposed a drastic weakening of a number of safety requirements that apply to the current generation of U.S. nuclear plants. These proposals include (1) use of a filtered, vented confinement building instead of a robust containment capable of preventing a large release of radioactive materials in the event of severe core damage; (2) a reduction of the size of the emergency planning zone (EPZ) from 16 kilometers to 400 meters; (3) a reduction in the number of staff, including operators and security personnel; and (4) a reduction in the number of systems whose components must meet the most stringent quality assurance standards.

However, there is insufficient technical justification for these measures. The presence of a pressure-resistant, leak-tight containment and the maintenance of comprehensive emergency planning are both prudent "defense-in-depth" measures that could mitigate the impact of a severe accident with core damage. Defense-in-depth is the requirement that nuclear reactors should have multiple, independent barriers in place to prevent injuries to the public and damage to the environment. The presence of multiple barriers is a hedge against uncertainty and an acknowledgement that the understanding of the performance of any one barrier is incomplete.

PBMR promoters claim that a robust containment is unnecessary because the design-basis depressurization accident cannot cause damage to the PBMR fuel severe enough to result in a large radiological release. They argue further that such a containment would actually be detrimental to safety because it would inhibit heat transfer and interfere with the passive mechanism needed to cool the core in the event of a loss-of-coolant accident. However, a containment is needed not only to inhibit the relatively minor releases that would occur during the design-basis accident, but also to mitigate the consequences of a more severe accident. Containments can also help to protect the reactor core from a sabotage attack utilizing truck bombs or hand-held rocket launchers --- an ominous possibility that should not be discounted.

The NRC concerns seem speculative in that it involves the postulation of potential core damage that has not been demonstrated to be possible by simulation. The mention of truck bombs and hand held rocket launchers takes us clearly into the realm of fantasy because the use of such weapons against a PBR can be defeated by relatively low tech security measures already used to harden high risk targets. What sort of major accident did the the NRC have in mind?

Among the largest sources of uncertainty for the PBMR are the potential for and consequences of a graphite fire. The large mass of graphite in the PBMR core must be kept isolated from ingress of air or water. Graphite can oxidize at temperatures above 400 C, and the reaction becomes self-sustaining at 550 C (the maximum operating temperature of the fuel pebbles is 1250 C)[1]. Graphite also reacts when exposed to water vapor. These reactions could lead to generation of carbon monoxide and hydrogen, both highly combustible gases.

If a pipe break were to occur, leading to a depressurization of the primary system, it has been shown that flow stratification through the break can cause air inflow and the potential for graphite ignition[2]. While the PBMR designers claim that the geometry of the primary circuit will inhibit air inflow and hence limit oxidation, this has not yet been conclusively shown.

The consequences of an extensive graphite fire could be severe, undermining the argument that a conventional containment is not needed. Radiological releases from the Chernobyl accident were prolonged as a result of the burning of graphite, which continued long after other fires were extinguished[3]. Even though the temperature of a graphite fire might not be high enough to severely damage the fuel microspheres, the burning graphite itself would be radioactive as a result of neutron activation of impurities and contamination with "tramp" uranium released from defective microspheres. An even worse consequence would be combustion of carbon monoxide, which could damage and disperse the core while at the same time destroying the reactor building, which is not being designed to withstand high pressure. In contrast, the large-volume concrete containments utilized at most pressurized-water reactors can withstand explosive pressures of about 9 atmospheres.

Here we must raise a question since the risk of graphite fire seems greatly exaggerated. General Atomics, which has some experience with the operation of Graphite core and fuel reactors, states,

NUCLEAR-GRADE GRAPHITES ARE NONCOMBUSTIBLE BY CONVENTIONAL STANDARDS"

The General Atomics statement adds:

because graphite is so resistant to oxidation, it has been identified as a fire extinguishing material for highly reactive metals, including zirconium.

The oxidation resistance and heat capacity of graphite serves to mitigate, not exacerbate, the radiological consequences of a hypothetical severe accident that allowed air into the reactor vessel. Similar conclusions were reached after detailed assessments of the Windscale and Chernobyl events; graphite played little or no role in the progression or consequences of the accidents. The "red glow" observed during the Chernobyl accident was the expected color of luminescence for graphite at 700°C and not a large-scale graphite fire, as some have incorrectly assumed.

The NRC has a more realistic concern, howbeeit, one would not lead to a major PBR accident:

First, the fundamental fuel behavior must be sufficiently well understood that a complete set of technical specifications for the fuel can be derived. It appears that this is not yet the case. There are numerous instances in which TRISO microspheres manufactured to identical specifications and irradiated under identical conditions exhibited drastically different fission product release behavior that could not be attributed to observed physical defects like cracking of the SiC layer[6]. This indicates that there are technical factors affecting TRISO performance that have not yet been identified.

Second, when a complete set of technical specifications is finally at hand, the PBMR fuel manufacturing process will have to be reliable enough to ensure that the specifications are met. Because PBMR fuel is credited to a greater degree than LWR fuel for maintaining safety under accident conditions, and is less tolerant than LWR fuel to defects, PBMR fuel will have to be subjected to more stringent quality control. However, even if the requirements were no more stringent for PBMR fuel than for LWR fuel, inspecting the enormous microsphere flow with a high enough sampling rate to ensure an adequately low defect level would be a considerable challenge. The number of TRISO microspheres manufactured annually to support ten PBMR modules (1150 MWe total) would be on the order of ten billion, three orders of magnitude greater than the number of uranium fuel pellets needed to supply an LWR of the same capacity.

Finally, even if the above two criteria are satisfied, there must be assurance that the behavior of the fuel will not be significantly worse than expected if conditions in the core deviate from predictions --- that is, the fuel should "fail gracefully." It is on this count that the current TRISO fuel technology is clearly a loser. While past experiments have shown that the SiC layer of TRISO fuel limits the release of highly hazardous radionuclides like Cs-137 to below 0.01% of inventory up to 1600 C, the retention capability is rapidly lost as the temperature continues to increase. At 1800 C, releases of 10% of the Cs-137 inventory have been observed, which is on the order of the release expected during a LWR core-melt accident[7]. Without a leak-tight containment present, the release into the environment would be comparable to the release from the fuel.

Thus in order to justify the absence of a leak-tight containment, Exelon needs to demonstrate that the PBMR maximum fuel temperature will not exceed 1600 C during the design-basis depressurization accident, and that more severe accidents that could cause higher fuel temperatures are so improbable that they do not need to be considered. However, given the uncertainties discussed in the previous section --- like a discrepancy between calculated and measured maximum temperatures of at least 130 C --- there are serious grounds for skepticism.

There is a strong element of the "not invented here" syndrome in the NRC statement, and the reminder that since the repair of the American nuclear safety establishment was never made good after the havoc that Milton Shaw visited on it.

There are still problems with PBR safety. Rainer Moormann, a German researcher who studied the decontamination of the decommissioned AVR, found an unexpectedly high level or radioisotope contamination in the decommissioned AVR. He attributed the contamination to fuel breakdown at high temperature. While Moormann's findings ought to be taken seriously, radioactive contaminants in a decommissioned experimental reactor built during the 1960's ought not by themselves seen as evidence of a fatal flaw in the reactor design. The AVR used something like 20 separate pebble designs during its over 20 year history. Moormann believes that the problem stemmed from the over heating of fuel pebbles within the reactor. This is most likely a fixable problem, but fixing it requires resources.

Alvin Weinberg who certainly understood the advantage of nuclear safety, viewed the successful design of large scale technological objects like reactors and the product of big science. Nothing can substitute for the large scale deployment of technological resources in seeking technological objectives. Unfortunately the sort of large scale nuclear establishment which the United States possessed in the 1950's and 60's. I would expect the Chinese to deploy the major resources needed to insure Pebble Bed Reactor safety. The Chines need the PBR simply because they need a low cost nuclear technology to replace hundreds of coal burning steam plants. If the politicians do not disrupt it, a safety culture should emerge within the Chinese nuclear community which will provide china and the world with a highly safe PBR. For society, nuclear defense in depth includes a strong nuclear research community that has the curiosity and the resources to investigate nuclear safety concerns ands identify safe materials, designs, and safe production and operation standards without political interference.