Monday, August 23, 2010

Weinberg on Nuclear Safety

By the middle of 1972 the handwriting was on the wall. Alvin Weinberg had some very powerful enemies, including Congressman Chet Holifield, and AEC administrator Milton Shaw. At the heart of their enmity was a distaste for Weinberg's view on nuclear safety. The official line of the Atomic Energy Establishment was that Light Water Reactor technology was mature and safe. Nuclear scientists who were worried about reactor safety were not sure. 7 years later the Three Mile Island-2 accident was to demonstrate that reactors, although not highly dangerous, were not as safe as they could be. Weinberg championed the cause of nuclear scientists who knew that more nuclear safety research was needed. The establishment, including Holifield and Shaw, found that Weinberg's stance was an unforgivable affront to their power and determined to fire him.

Weinberg's firing followed another incident, the forced censorship of a K.Z. Morgan paper, with a threat that if Morgan presented a notion that certain parties in Washington, Chicago and Arco, Idaho did not like, namely that the the Molten Salt Breeder Reactor (MSBR) was a safer and more acceptable than the Liquid Metal Fast Breeder Reactor (LMFBR), Laboratory funding, effecting the livelihood of hundreds of Laboratory employees would be cut. Alvin Weinberg came close to confirming Morgan's story that ORNL had been threatened with a funding loss had Morgan's uncensored paper been presented. This threat could have only been a serious threat if it came from Holifield and Shaw. As it was the staff of ORNL diminished from 5300 to 3600 during the late 1960's and early 1970's as the result of funding decreases including the termination of the Molten Salt Reactor development program.

As it turned out, censoring Morgan did not protect Weinberg, because Chet Holifield disliked Weinberg's stance on nuclear safety. Weinberg was later to be proven right on nuclear safety problems at a place called Three Mile Island.

From the late in the 1960's until the end of December 1972, Weinberg had worked to shift the direction of the laboratory focus away from reactor development and toward environmental issues. He succeeded in creating a major center for the study of carbon in the environment, at a time when so-called environmentalists favored burning CO2 to nuclear energy. Indeed because of Weinberg's intuitive, ORNL moved a generation ahead of Snowmass and almost everywhere else in its thinking about carbon and the environment. In November, 1972 the recently-fired Alvin Weinberg, six weeks away from a year long terminal leave from ORNL, journeyed to Boulder, Colorado to speak to Council for the Advancement of Science Writing about nuclear safety. Weinberg, whose integrity on nuclear safety was unquestionable, took environmentalists to task for their preference for fossil fuels over nuclear power. Weinberg stated,
Nuclear power plants and their subsystems have caused less damage to human health and to the environment, per kilowatt-hour, than have fossil-fueled central power stations. Thus Professor Lester B. Lave of Carnegie-Mellon University points out that from mining alone the damage imposed by coal is twelve-fold greater, per kilowatt-hour, than is that imposed by nuclear energy. (Professor Lave's argument is based on the fact that some 120,000 coal miners today receive about $300 per month compensation as the result of black lung disease.) C. Starr, M. A. Greenfield, and D. F. Hausknecht writing in Nuclear News, Oct. 1972, have compared the radioactivity hazard from nuclear plants with that from oil- or coal-fired plants. Their results show that to reach air quality standards for oxides of sulfur and nitrogen and radioactivity in Los Angeles County one could tolerate 160,000 nuclear plants of 1,000,000-kilowatt capacity, but only 10 oil-fired or 23 natural-gas plants of this size.

Granted that properly operating nuclear power plants and their sub-systems - including mining, transport and chemical reprocessing of used reactor fuel elements, and disposal of radioactive wastes - are benign and have been so demonstrated, are there concerns regarding the possibility that these systems may malfunction and cause hazard to people and to the environment? This is a perfectly legitimate question that deserves serious and thoughtful consideration; and it is this aspect of the matter that I shall address.

A properly operating nuclear power plant and its subsystems is and can remain as innocuous a thermal power plant as man has ever devised. The whole safety issue then centers around the possibility that a nuclear plant or its subsystems may malfunction so grossly as to cause damage to the environment or to people.
Weinberg has laid out the issues. The issue in November 1972 is the same which confronts us, 38 years later. The so-called "Greens" have made a secret alliance with fossil fuel interest that is to the detriment of all life forms on the planet Earth, including its human inhabitants. And no matter how much environmentalists profess to be concerned about the carbon problem, until they give up their anti-nuclear alliance with coal and natural gas interests, the safety of the planet is in jeopardy.

Environmentalists, who seemingly regard lies as a primary tool to further their anti-nuclear arguments, have long insisted that the scientific-technical community had ignored the issue of nuclear safety. Weinberg answered this slur,
At the outset, we must remember that the technical community has always recognized that a nuclear system is potentially a dangerous device.
This statement can be verified by anyone who would care to review the history of nuclear safety discussions and research, by pioneering nuclear scientists, as Weinberg pointed out,
I can assert that nuclear systems per kilowatt-hour have caused much less damage to the biosphere than have other sources of thermal energy, is a tribute to the ingenuity and foresight of the reactor engineer. From the earliest days of nuclear energy we nuclear people have been constantly reminded of this potential danger. (In 1942 one of the first jobs I did for the Manhattan Project was to estimate the hazard caused by minute amounts of radioactive carbon that would be emitted from the early air-cooled graphite reactors; and General Leslie R. Groves insisted that Enrico Fermi move his West Stands critical reactor from the center of Southside Chicago because of the potential hazard.) Being so sensitively attuned to this potential, we have developed techniques and methods for handling these materials safely. The question is, successful as we have been in the past, what can we say about the likelihood of our continuing success in the future when large nuclear energy reactors will dot the landscape everywhere?
Weinberg in 1972 addressed what continue to be nuclear safety concerns of the public:
The whole nuclear power system involves four subsystems:
(1) mining and refining uranium to fuel the reactor;
(2) the reactor itself;
(3) transport and chemical processing of radioactive materials from the reactor; and
(4) waste disposal.
After discussing research on cancer rates of uranium miners, Weinberg concluded,
the number of deaths caused by mining of uranium, per kilowatt-hour, is much less than those from mining of coal, simply because there are so many fewer miners involved per kilowatt-hour.
It should be noted that changes in mining technology during the last 40 years have improved the health and safety of all miners, but this is particularly true of American uranium miners, because uranium mining technology now does not require miners to go underground. Coal miners still die in deep underground mines, and workers at oil and gas extraction facilities still die from natural gas explosions. So if anything there is an even greater safety advantage in uranium mining today than when Weinberg spoke 38 years ago.

Weinberg noted two safety concerns in connection with reactors,
There are two quite different potential hazards from a nuclear reactor.
* First there are the routine effluents - including tritium which is a radioactive form of hydrogen, radioactive fission gases from possible leaking fuel elements, radioactive cobalt from corrosion products, etc.
* Second there is the question of a major, catastrophic accident to a nuclear reactor that might result in an appreciable fraction of the radioactive inventory being released to the environment.
Weinberg noted that the first hazard was itself controversial, but noted that even disregarding the controversy,
the current standards are now so low - 5% of the amount we receive from natural sources - at the reactor site boundary as to make the whole issue a non-issue. [By comparison, the added radiation one gets by sleeping adjacent to one's wife whose body (as does everyone's) contains radioactive potassium, is around 7% of the standard for the reactor site boundary. This is a classic case of balancing benefits versus risks!] And indeed, nuclear power plants are now designed to meet these very stringent requirements, and in fact are doing so; here a technological
fix has completely resolved a controversy.
Weinberg thus points out a reductio ad absurdum of the safety concerns of nuclear critics. It is, Weinberg argues, more dangerous from a radiation safety viewpoint to sleep next to your spouse than to sleep just outside the fence at a reactor site.

We now have reached a point where we should look for Alvin Weinberg's covert comments about his firing, which was a closely-guarded secret at the time. First it should be noted that ORNL had been between 1955 and 1965 a major international center for reactor safety research. A team of reactor chemists under the direction of George W. Parker had examined the circumstances of a potential reactor accident. My father from 1960 to 1965 had been a member of the team, and played a major role in writing a 1967 paper which described the team's work. I have noted elsewhere Milton Shaw's role in shutting down ORNL safety research. However, in their swan song, the ORNL safety researchers noted,
In conclusion, we wish to emphasize that there are many factors affecting the fission product source term and the amount of fission products which actually can escape the containment system of power reactors in reactor accidents. While the amount of fission products evolved from overheated fuel is highly useful information, it is now recognized that the hazard of reactor accidents can be fully evaluated only through sophisticated accident simulation experiments in facilities such as the Containment Research Installation (ORNL), the Containment Systems Experiment (Battelle Northwest), and the Loss-of-Fluid Test (Phillips-Idaho).
This recommendation was important in Weinberg's thinking. And it was a thorn in Milton Shaw's side. The loss of coolant test was the critical issue for Weinberg, because speculation had held that once core meltdown had occurred, nothing could stop the molten mass of core materials from eating its way through the massive steel pressure vessel, the cement floor of the underneath the reactor, and into the earth, all of the way to China. This was the infamous "China Syndrome." The loss of coolant test proposed to sacrifice a built-to-purpose reactor under construction at INL. A loss-of-coolant accident was to be simulated, and the reactor was then allowed to experience core meltdown. The goal of the experiment was to discover if the "China Syndrome" could in fact happen. Weinberg argued that the loss of coolant experiment was rational.
As long as reactors were relatively small we could prove by calculation that even if the coolant system and its back-up failed, the molten fuel could not generate enough heat to melt itself through the containment However, when reactors exceeded a certain size, then it was no longer possible to prove by calculation that an uncooled reactor fuel charge would not melt through its containment vessel. This hypothetical melt-through is referred to as the China Syndrome for obvious reasons. Since we could not prove that a molten fuel puddle wouldn't reach the basement of a power reactor, we also couldn't prove whether it would continue to bore itself deeper into the ground.
Weinberg pointed to the consequences,
Whether or not the China Syndrome is a real possibility is moot. The point is, however, that it is not possible to disprove its existence. Thus, for these very large reactors, it is no longer possible to claim that the containment shell, which for smaller reactors could be relied upon to prevent radioactivity from reaching the public, was sufficient by itself. In consequence, the secondary back-up cooling systems, which originally were designed simply to prevent property loss and awkward clean-up, must now be viewed as the ultimate emergency protection against the China Syndrome and as an integral part of the reactor safety system.
I have already pointed out that it was not Weinberg alone, but the community of Nuclear Scientists which did not accept Milton Shaw's judgment on nuclear safety. As Weinberg pointed out,
Very arduous and sometimes acrimonious [Congressional] hearings related to these criteria were held last year [1971]. During this time every aspect of the operation of the emergency core cooling systems both in pressurized-water reactors and in boiling-water reactors has been thoroughly re-examined. Although they are obviously cumbersome, the hearings have obliged all parties, intervenors, manufacturers, the AEC, safety engineers, to examine in excruciating detail the possible course of events following a loss-of-coolant accident. The criteria that have emerged represent additional conservatism in the design both of light-water reactors and of their emergency core cooling systems.
There is little reason to doubt that Weinberg saw the "China Syndrome" controversy as the backdrop to his firing.

Weinberg then took up the issue of the transportation and chemical reprocessing of nuclear fuel. Weinberg argued that these problems should be addressed together because,
if reactors and chemical plants needed for reprocessing their fuel were built very close to each other (in nuclear parks) the transport problem as a separate safety hazard would largely disappear.
Weinberg knew of one such system, the Molten Salt Breeder Reactor that was being developed at Oak Ridge. Weinberg noted,
As for the chemical fuel reprocessing plants themselves, we at Oak Ridge National Laboratory are studying measures that might be taken to reduce radioactive emissions from such plants as low as those from light-water reactors - around 5% of radiation levels from natural sources at the plant boundaries. We believe that plants with practically zero release are actually quite feasible and would probably add around 0.5 mill per kwh to the cost of nuclear power.
Weinberg also reported that he had testified
before the Senate Interior and Insular Affairs Committee in October 1971, . . .
And his views had, no doubt given pain to Milton Shaw and Chet Holifield,
our present technology and philosophy of siting separates the chemical plants from the reactors, and so we are confronted with the necessity of transporting heavily radioactive materials. To estimate the hazard, let us suppose that by the year 2000, we have 1,000,000 megawatts of nuclear power, of which two-thirds are liquid-metal fast breeders. There will then be 7000 to 12,000 annual shipments of spent fuel from reactors to chemical plants, with an average of 60 to 100 loaded casks in transit at all times. Projected shipments might contain 1.5 tons of core fuel which has decayed for as little as 30 days (in which case each shipment while in transit would generate 300 kilowatts of heat) and 75 million curies of radioactivity. Present casks from light-water reactors might contain material that produces 30 kilowatts of heat and contains seven million curies of radioactivity.
It should be noted that sometime later, reactor researchers at Argonne National Laboratory redesigned the fuel reprocessing system for the LMFBR in order to keep it in the same location as the reactor. Not only did they tastily acknowledge that Weinberg was right, but they also managed to spend a huge amount of money to reinvent the wheel, that is to develop a technology that could do for LMFBR fuel what ORNL was developing technology for with the MSBR, using analogous molten-salt technology.

Finally, Weinberg offered some observations on nuclear waste. Ironically, Weinberg did not realize that ORNL had developed a solution to the nuclear waste problem. My father had in the 1950's investigated the use of plutonium as a Molten Salt Reactor fuel. And the use of Plutonium as a molten salt reactor fuel had been demonstrated during the Molten Salt Reactor Experiment. Weinberg acknowledged the problem created by plutonium in used nuclear fuel,
Plutonium-239 has a half-life of 24,400 years, and wastes containing this nuclide will remain potentially dangerous for 200,000 years.
Ironically, if plutonium and the so-called minor actinides could be burned in a reactor, they would cease to be a part of the nuclear waste problem, the highly-radioactive fission products in nuclear waste would stop being dangerous after 300 years. Thus another solution to the nuclear waste problem was potentially available from Oak Ridge technology, but that had not been worked out yet. That solution could potentially produce a very large amount of new energy. Two decades later, Uri Gat and J.R. Engel of ORNL and H.L. Dodds of the University of Tennessee, were to write,
The MSRs, with their continuous processing and the immediate separation of the residual fuel from the waste, simplify the handling of the waste and contribute to the solution and acceptability of the waste issue.
The on-line processing can significantly reduce the transportation of radioactive shipments. There is no shipping between the reactor and the processing facility. Storage requirements are also reduced as there is no interim storage for either cooldown or preparation for shipment. The waste, having been separated from the fuel, requires no compromise to accommodate the fuel for either criticality or diversion concerns. The waste shipments can be optimized for waste concerns alone. The actinides can be recycled into the fuel for burning and thus eliminated from the waste. While further work is required to fully analyze this possibility, several proposals to burn actinides have been made. The MSRs with on-line processing lend themselves readily to recycling the actinides into the fuel. Eliminating the actinides from shipments and from the waste reduces the very long controlled storage time of the waste to more acceptable and reasonable periods of time
I must first state than nothing Weinberg had to say about alternative solutions to the nuclear waste problem was wrong. It is simply that using plutonium and other actinides from nuclear waste, as nuclear fuel, kills two birds with one stone. Not only does it turn what was considered dangerous waste into energy, but it will allow for hundreds and perhaps even thousands of thorium breeding molten salt reactors (LFTRs) to be started very quickly, since their initial fuel charge could be recovered from used nuclear fuel. Thus the supposedly terrible problem of nuclear waste, actually is part of a workable solution to the problem of post carbon energy.

Alvin Weinberg made important contributions to our understanding of the role of energy in our society, and those contributions have, as of yet not been fully appreciated. He understood both the problems and the potential of nuclear energy. In many respects Alvin Weinberg correctly saw path that society was taking, and gauged its consequences. Although not the first nuclear scientist to recognize the CO2 problem, that honor goes to Edward Teller, once Weinberg understood the carbon problem, he emerged as a leading voice in articulating it during the 1970's.

What Weinberg failed to realize was the extent to which ORNL scientists, under his leadership, had found a way out of "the Faustian bargain" which he frequently referred to as a description of the relationship between the nuclear science community and society. Undoing Weinberg's "Faustian bargain" will thus be a topic for a further post.

1 comment:

NNadir said...

Nice overview of this great man's contribution Charles.

He was a prophet way adhead of his time.


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