Sunday, January 13, 2008

Power Reactor Safety:Myths and Facts

My father collaborated with George Parker on this 1994 essay on Nuclear Safety. Both men were long retired from ORNL, although Parker continued to work part time as a consultant. Their experience gave them a unique perspective on the safety problems of Light Water Reactors. They were anything but "yes" men to the "nuclear industry." During the early 1970's AEC executive Milton Shaw was bitterly opposed to the nuclear safety research at ORNL. Shaw and Chet Holifeld conspired to fire Alvin Weinberg who insisted that reactor safety could be improved. Shaw also for a time curtail funding for George Parker's research on safety issues caused by reactor core melt down. I doubt that Milton Shaw was a fan of my father either. The concern about the safety and health issues of coal was one of my fathers concerns. During his last few years at ORNL he had become increasingly concerned about human exposure to radiation from natural sources. Together between 1977 and 1995 my father and Gorge Parker wrote a number of essays in defense of the safety of nuclear power. In addition my father wrote essays on his own.

Power Reactor Safety:Myths and Facts

Charles J. Barton and George W. Parker

Fear of radioactivity and myths concerning the safety of nuclear reactors have abounded since the early days of the nuclear power industry. Critics of nuclear power, with the whole—hearted support of news media, have fanned these fears and supported the myths. The extensive literature written by experts that gives a drastically different view of these subjects has been consistently ignored in news reports. Richard Roberts, Assistant Administrator for Nuclear Energy of ERD (The predecessor of the Department of Energy) recognized the problem in 1976. He said that the problem is not so much the technology but the challenge of communicating where we are, where we are going, and what our capability is. He also mentioned that our nation at that time seemed to he swept by a virulent form of “nuclear phobia’ exhibited by disbelief in any encouraging thing that experts in the nuclear energy area might say. it appears to us that there has been little if any improvement in this situation in the last 18 years and this article is a belated response to Roberts challenge to: Do whatever we can to blow away the smokescreen that has enshrouded the energy debate and the nuclear program. We will deal first with a comparison of health effects of generating electricity with nuclear reactors and coal burning plants followed by a discussion of accidents in operating nuclear reactors and the safety of nuclear power plants. Finally, the belief that technology for developing facilities for long—term disposal of high—level nuclear wastes does not exist will be discussed.


The myth that seems to be commonly accepted in this country is that it more dangerous to the health of people living in the vicinity of electric power plants to generate electricity by using nuclear reactors than by burning coal. 1980 survey showed that 80 percent of the American public shared this belief. In recent years publicity on the greenhouse effect (warming of the atmosphere from increasing concentration of carbon dioxide) and acid rain has caused a few critics of the nuclear power industry to modify their opposition to nuclear power. Approximately 50 percent of the electricity in this country comes from coal—burning plants and we will continue to be heavily dependent on this readily available fossil fuel. We need to give careful thought to our choice of technology to meet our increasing need for electricity.

Most people tend to think about health effects of electricity generating plants solely in terms of effluents from the plants. Comar and Sagan at the Electric Power Research lnstitute pointed out that it is necessary to consider the complete fuel cycle. For coal—burning plants the cycle includes mining, transportation, burning the coal and disposal of the ash. For nuclear plants the cycle includes mining, enrichment of uranium and conversion to uranium dioxide fuel, consuming the uranium in a nuclear power plant and disposal of the used fuel.

Comar and Sagan considered both disease and accidents in calculating health effects from each step in the two cycles which they expressed in terms of premature deaths per year among the population living in the vicinity of 1000 megawatt power plants. The mining and transportation of coal and the mining of uranium made major contributions to the total health effects of the two cycles. For coal plants the estimate ranged from 2 to 116 while for nuclear plants it ranged from 0.11 to 1.0. This comparison shows that, so far as routine operation of the different types of power plants is concerned, the health effects of nuclear plants is no worse than that of coal—burning plants and may be better. The wider range of estimates for the latter plants is due to the fact that the health effects of radioactive materials is much better known than the effects of the effluents from coal combustion.


The second myth that we will discuss is that, because operating reactors contain large quantities of radioactivity, they are inherently unsafe. One nuclear power critic stated in the wake of the Chernobyl reactor accident : ‘There is tremendous uncertainty. mi reactors have a severe accident potential. I’ This potential was recognized in the early days of the the development of nuclear reactors and a tremendous effort has been made to minimize the likelihood that reactor accidents will result in loss of life or extensive property damage. We will discuss the three accidents in operating reactors that resulted in release of significant quantities of radioactivity: Windscale Pile No. 1, Three Mile Island and Chernobyl. Of these, only the latter resulted in deaths and large—scale property damage. We will compare these accidents and give reasons for our belief that loss of life from accidents in modern light—water nuclear power producing plants is unlikely.

Windacale Pile No. 1. The Windscale reactor was used to produce plutonium. In October 1957, during use of a procedure to release energy stored in the graphite moderator, the temperature in part of tne reactor became high enough that some of the metallic uranium slugs and the nearby graphite moderator began to burn, releasing fission products through the stack that discharged air used to cool the reactor. effort to quell the fire with carbon dioxide was unsucessful and it was finally quenched by the introduction of a large quantity of water. The accident made this reactor unusable.

Three Mile Island (TNI-2). This reactor located near Harrisburg, Pennsylvania is the site of the most serious US. reactor accident to date and the only major accident in a large light—water reactor to date. Early on Aprii 28, 1979, a series of events at this reactor began that resulted in a loss—of--coolant accident. (LQCi4). fln early report characterized the accident as a unique combination of failures, design deficiences and operator errors. The critical error was the action of an operator who shut down the high—pressure injection of water that started automatically two minutes after the reactor shut down. If this water injection had been allowed to continue, the reactor core would have remained under water and serious core damage would have been avoided. Steps have been taken to eliminate the design deficiences and operator errors revealed by this accident.

Chernobyl—4. This accident occurred about 80 miles north Kiev, Ukraine, in April and May, 1986. Russian report that was published several months later stated that the accident took place because of a variety of poorly conceived actions and procedures related to an experiment that was being conducted during an otherwise routine shut down of the reactor. Human errors compounded by a lack of proper procedures resulted in overriding of safety protection systems and to react.or failure evidenced by two explosions, one after the other, apparently caused by a prompt critical reactivity excursion (a sudden increase in the rate of fissioning in the reactor resulting in production of a large amount of heat in the reactor core) and steam or hydrogen explosion. The explosions blew the top off the reactor core container and the top off the the building in which the reactor was housed. The very hot reactor core released fission products directly to the atmosphere as the hot graphite moderator continued to burn until large quantites of boron carbide, lead, dolomite, sand and clay (5000 tons total) were dumped on the core by helicopters hovering over the reactor.

A report published in 1987 listed the known human casualtites of this accident as 203 persons hospitalized and 31 deaths. It seems unlikely that we will ever know all the human consequences of this accident which include an unknown number of deaths from over—exposure to radiation and disruption in the lives of thousands of people who were relocated on very short notice.


There are significant differences in the three accidents described above. The Windscale reactor, used only for production of plutonium, was fueled with metallic uranium slugs which were surrounded by a large quantity of graphite moderator and cooled by air. Thus plenty of oxugen was available to burn both the fuel and the graphite when the temperature got out of control. There were almost no containment provided for fission products released from the burning fuel. Filters were installed in the (reactor ventelation) stack through which the, hot air was discharged which [trapped] at least a part of the radioactive particles released by the fire but noble gases (mainly krypton and xenon) and iodine were retained.

Chernobyl—-type reactors (RBI’IK-l00) use uranium dioxide pellets encased in a zirconium alloy as do all water—cooled reactors including TMI—2. The fuel rods are surrounded by a larger zirconium alloy tube through which cooling water flows. The quantity of water present in the reactor core is much smaller than t.hat in pressurized and boiling water reactors.
amount of zirconium alloy, which is converted to brittle zirconium oxide when exposed to high—temperature steam, is greater than in light water reactors. The reaction between zirconium and steam produces hydrogen which, when mixed with or oxygen, makes an explosive mixture. In addition to the chemical hazards, the design of the Chernobyl reactors makes them more difficult to control and, in fact, the operators of Chernobyl—4 allowed a situation to develop where the reactor out of control. This set of circumstances cannot be duplicated in light—water—moderated reactors.

The point of this comparison of the three reactor accidents is to make it clear that the potential for accidents is much greater for the Windscale and the Chernobyi reactors than in light water reactors. More important, however is the design and construction of these reactors which includes a very thick steel core container and a thick steel—reinforced building around the reactor. Multipie safeguards are provided, some of which have been greatly improved as the result of the lessons learned from the TM1-2 accident.

A comparison of fission products relesed in the three accidents reveals some important differences. Radioactive iodine (1—131) is a particular hazard in reactor accidents because it concenrates in the human thyroid through drinking contaminated milk or eating contaminated vegetables. The amount of this fission product released in the three accidents is (in curies):
Windocale, 20,000; T1il—2, iS to 30 Chernobyl—4, 7.3 million. The low level of iodine release from TMI—2 is believed to be due to the solubilty of the iodine in water, possibly because it combines with cesium, another fission product, to make cesium iodine. The noble gases have a very low solubiity in water and the release of these gases from TI’lI—2 is estimated to be in the rarnge 2.4 to 17 million curies as compared to 340,000 from Windscale and about 46 million from Chernobyl—4. These gases are not retained by the human body and their principal hazard is skin exposure. in the TNI—2 accident, no one received a greater dose from exposure than the average U.S. citizen receives annualy from natural radioactivity. Significant quantities of other fission products were released only in the Chernobyl accident (estimated total 22 million curies). t. TNI—2, the solubility of these fission products in water probably helped to minimize trieir release and filters in the hot air discharge tower apparently caught most of the solid materials produced by the partial burning of the Windscale reactor core.

Information Handling it TMI—2. Mental stress among the people living in the vicinity of TI1I—2 was judged to be the principal health effect of this accident. This has been ascribed in large measure to poor information handling. Initially, the plant operators were slow to recognize the seriousness of the accident and when higher authorities became involved, including the Nuclear Regulatory Commission, their lack of preparation for handling both the accident and relations with the news media became evident. The latter proceeded to fan the public’s already strong fear of radiation. The unneeded action of the governor of Pennsylvania in ordering the evacuation of children and pregnant women living within five miles of the plant accentuated these fears. It appears that. regarding the mishandling of news from TNI—2, there was more than enough blame to to around.

Operating Record of Light Water Reactors. The world list of nuclear power plants published in Maich 1994 showed a total of 418 such plants then in operation with a total electricity generating capacity of 406,000 megawatts. large fraction of this number is comprised of pressurized water reactors (239) and boiling water reactors (81). The total number of these light water reactors operating in the U.S. where they were developed is 108. Many of these have been operating for years. cDIn impressive total number of reactor—years of operating experience, with only one serious accident, which did not result in life—threatening radiation exposure to anyone in or around the plant, is a strong argument against the myth that reactors are inherently unsafe.


The final myth that we will consider is the claim that technology to develop facilities for safe long—term disposal of high—level nuclear wastes is not available. The success of the anti—nuclear people in perpetuating this belief is demonstrated by a 1980 poll which showed that only 2% of Americans were confident that the U.S. had that expertise.

In the U.S., disposal of hign—level wastes has been complicated by the decision made during the Carter administration to forbid the reprocessing of used nuclear fuel. That decision was based on the perceived need to minimize the world—wide availability of plutonium to make nuclear bombs. Other nations with operating reactors did not follow the U.S. example which had little if any effect on proliferation of nuclear bomb capability. The British and French have successfully operated fuel reprocessing plants which make unused enriched uranium and plutonium available for reuse in their reactors and greatly reduces the volume and the radioactive life of their nuclear wastes. The Japanese are also developing this capability. The best way of disposing of plutonium is to burn it in nuclear power plants.

cm extensive effort has been expended in the U.S. to develop facilities for long—term, storage of high—level nuclear waste. In the 1360s, scientists in the Health Physics Division of the Oak Ridge National Laboratory were well on their way to demonstrating the feasibility of storing such wastes in unused underground salt mines in Kansas when politicians became involved and killed the project, setting the example for opposition to subsequent efforts in other states. The NINBY factor (not in my back yard) has inhibited disposal of all types of wastes throughout this country but the fear of radioactivity among the general public, combined with the dedicated efforts of opponents of the nuclear power industry, makes opposition to nuclear waste disposal sites particularly vulnerable even in sparsely populated areas. There is no doubt in our minds that technical expertise to construct safe and reliable disposal facilities for high level wastes does exist in this country and has already been demonstrated in several other counties. Use of abandoned underground salt mines, such as those near Carlsbad, New Mexico, and the Yucca facility under development in Nevada appear to be quite suitable for this purpose.


Plans for second generation nuclear power plants designed to be even safer to operate than those now in use are presently available. If the U.S. public could be convinced that the myths discussed in this article are untrue, it would expedite progress toward demonstrating the feasibility of expanding use of nuclear power generating plants. The desirability of reducing the amount of sulfur dioxide and carbon dioxide into the atmosphere from coal burning plants is well recognized and nuclear power is at present the most environmentally acceptable alternative for meeting our expanding need for electricity. There is a need for U.S. citizens to look beyond the media hype on the danger of reactor accidents such as that which surrounded the TNI—2 accident and for experts in the nuclear industry to make greater efforts to communicate facts to the public to replace the information being supplied by anti—nuclear groups and uninformed or poorly informed media writers and TV personnel.

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