In December 2011, the government of Japan announced with great fanfare that the nuclear reactors damaged in March at Fukushima Daiichi were in a state of “cold shutdown” and that the release of radioactive materials from the reactor containment vessels had been brought under control. Read more >
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July 20, 2012 3:27 PM EDT
The National Academy of Sciences (NAS) is working on a study called “Lessons Learned from the Fukushima Nuclear Accident for Improving Safety and Security at US Nuclear Plants.” It is currently in the phase of collecting information through public meetings.
Dave Lochbaum and Ed Lyman were part of a small group of people who addressed the NAS panel yesterday. The slides from their presentation are available here.The others addressing the panel were two representatives from the Nuclear Regulatory Commission—Mike Johnson, deputy executive director for Reactor and Preparedness Programs, and Rob Taylor, deputy director of the Japan Lessons Learned Project Directorate—and Marv Fertel, president and CEO of the Nuclear Energy Institute, the nuclear industry trade association.
The NAS website says the report will address the following issues:
1. Causes of the Fukushima nuclear accident, particularly with respect to the performance of safety systems and operator response following the earthquake and tsunami.
2. Re-evaluation of the conclusions from previous NAS studies on safety and security of spent nuclear fuel and high-level radioactive waste storage, particularly with respect to the safety and security of current storage arrangements and alternative arrangements in which the amount of commercial spent fuel stored in pools is reduced.
3. Lessons that can be learned from the accident to improve commercial nuclear plant safety and security systems and operations.
4. Lessons that can be learned from the accident to improve commercial nuclear plant safety and security regulations, including processes for identifying and applying design basis events for accidents and terrorist attacks to existing nuclear plants.
The two-year study is due out in 2014.
August 31, 2011 6:00 AM EDT
On Friday, August 19, the Nuclear Regulatory Commission (NRC) released its initial response to the recommendations of the Fukushima Near-Term Task Force. The NRC did not address the substance of the Task Force recommendations, but only the process for further evaluating them. The NRC’s response, in the form of a “Staff Requirements Memorandum” (SRM), represents an attempt at reconciling the often differing views of NRC Commissioners.
A core dispute hinged on whether the Commission should vote within 90 days to move forward with any of the 12 recommendations provided by the Task Force, or instead require the staff to analyze the issues further and provide additional opportunities for external input. Chairman Jaczko said there was sufficient analysis at this point to move forward on voting on the recommendations within 90 days, noting that this would be only the first step and that there would be further opportunities for Commission guidance, such as rulemaking proceedings.
A majority of the Commissioners, however, believed that a process should be instituted for NRC staff and external “stakeholders” (e.g., the nuclear industry and non-governmental organizations) to have the opportunity to review, analyze, and comment on the recommendations before the Commission votes on whether to adopt them.
As a result, the majority view prevailed, and in the August 19 SRM the Commission ordered the staff to produce a draft charter to guide the review process, which will involve the creation of a senior-level NRC steering committee. The Commission also required the staff to provide two additional papers after 21 days and 45 days, which would contain further proposals on prioritizing the Task Force recommendations. Each of these papers will have to be voted on by the Commission. In addition, the Commission requested the Advisory Committee on Reactor Safeguards (ACRS) to formally review the Task Force recommendations, as well as the staff’s evaluation and prioritization of the recommendations.
Finally, the Commission segregated the first recommendation of the Task Force from the others and put it on a much slower track, requesting a staff paper in 18 months. This recommendation is an overarching one that would require a change in the Commission’s policy on how “severe” accidents would be regulated. This is a slower track than is warranted. Although this recommendation is not itself an urgent matter, it could facilitate implementation of other recommendations that do address urgent safety matters. Deferring action on this recommendation could therefore be counterproductive in the long run. This is also an issue the NRC has been considering for decades. Six months should be adequate time for the staff to develop a proposal based on this recommendation.
UCS, as a stakeholder in the process, certainly appreciates the interest of the NRC in developing a process to receive input from external groups. For instance, we would like the NRC to give due consideration to our own recommendations for strengthening nuclear safety, which contain some elements not addressed adequately by the Task Force.
However, UCS does not wish to see a repeat of the NRC’s sluggish response to the 9/11 attacks. In that case, even though the NRC issued a series of orders known as “compensatory measures” in February 2002 to quickly address security vulnerabilities that became apparent after 9/11, the NRC and the Nuclear Energy Institute (NEI), which was representing the nuclear industry, did not even come to agreement on what the orders meant or how they should be implemented until nearly five years later. The guidance was not fully implemented at all plants for five and a half years, and the NRC did not complete its inspections until December 2008—nearly six years after the orders were issued. NEI’s role in this delay is a demonstration as to why “stakeholder” input into regulatory processes is not always beneficial.
UCS believes that many of the Task Force’s recommendations for near-term action, such as addressing gaps in the protection of nuclear plants against natural disasters, can and should be approved quickly with a minimum of additional analysis. The process as outlined in the NRC’s Staff Requirements Memorandum will not necessarily conflict with this goal, but it will all depend on the staff’s plan as approved by the Commission. The Commission should not create a process that allows for open-ended negotiation with NEI on every technical and regulatory issue.
Coming four days after the SRM was issued, the August 23 earthquake in Mineral, Virginia should be a further call to action for NRC. That magnitude 5.8 earthquake caused ground motion that exceeded the “design basis” at the nearby North Anna nuclear plant, even though Dominion, the plant operator, originally had said the plant was designed to withstand an earthquake of magnitude 5.9-6.2.
This event highlights the knowledge gaps in seismic protection at US nuclear plants and supports the Task Force’s recommendation that the NRC should “order licensees to reevaluate the seismic and flooding hazards at their sites against current NRC requirements and guidance, and if necessary, update the design basis and SSCs [structures, systems, and components] important to safety to protect against the updated hazards.”
The American public deserves swift action—before the next surprise hits—to address safety problems that have been allowed to fester unresolved for too long.
August 1, 2011 10:54 PM EDT
Today we released our critique of key recommendations by the Nuclear Regulatory Commission’s (NRC) near-term task force in response to the Fukushima Dai-ichi nuclear accident earlier this year.
Three of the five NRC commissioners have now voted to not put its own task force recommendations on the fast track, arguing that the NRC needs more information to proceed.
However, if the NRC balks at implementing new safeguards in a reasonable time frame on the grounds that it doesn’t have enough information about what happened in Japan, then the agency also doesn’t have enough information to relicense operating reactors or license new ones. If the NRC commissioners need more time to sort out the lessons of Fukushima, there should be a moratorium on relicensing old reactors and licensing new ones until they do.
On July 13, we released our own set of recommendations to the NRC, taking a much broader approach.
July 29, 2011 11:28 PM EDT
UCS has obtained a preliminary analysis by the Nuclear Regulatory Commission (NRC) of a hypothetical severe accident at a nuclear power plant in Pennsylvania very similar to the one at Fukushima Daiichi. The NRC analysis finds that—even assuming early evacuation of the area—the accident could cause nearly 1,000 cancer deaths among the population within 50 miles of the plant, on average. Under unfavorable weather conditions, that number could be much higher.
The October 2010 draft report, which UCS obtained under the Freedom of Information Act (FOIA), contains some of the results of a long-delayed NRC study known as the State of the Art Reactor Consequence Analyses (SOARCA) project. The NRC initiated SOARCA in 2005 to provide “updated and more realistic analyses of severe reactor accidents.”(Links to the report are given at the end of this post.)
In part, the purpose of SOARCA was to show that such accidents would not be as bad as previous NRC studies had indicated. However, the new study shows that, at least for the 50-mile population, the average predicted risk of cancer deaths is only a factor of 3 lower than if one assumes the worst-case radiation release characteristics used in the 1982 study known as “CRAC2.” Given the large uncertainties associated with studies of this kind, a difference of a factor of 3 is not significant, so one can conclude that SOARCA essentially confirms, rather than refutes, the results of past studies.
The SOARCA report analyzes the consequences of an earthquake-induced “station blackout”— the total loss of off-site and on-site alternating current (AC) power—at the Peach Bottom nuclear power station in southeast Pennsylvania. This is exactly what happened at the Fukushima nuclear plant. Moreover, Peach Bottom consists of two General Electric Mark I boiling-water reactors. These reactors, known as BWR/4’s, are similar to Fukushima Daiichi units 2, 3, 4 and 5. Thus the event chosen by the NRC to analyze in detail several years ago was uncannily close to the Fukushima Daiichi accident.
The NRC report evaluates two different station blackout (SBO) scenarios. In one of them, known as a long-term SBO, station batteries, which provide direct current (DC) power, continue to operate until they are exhausted, assumed to occur after 4 hours. The batteries cannot power the main coolant systems, but they can provide enough electricity to maintain the instrumentation systems and operate certain valves, allowing operators to manually operate an auxiliary cooling system (known as the Reactor Core Isolation Cooling System, or RCIC) for some period of time.
If additional sources of electrical power are not brought online before the batteries are exhausted, however, operators lose control of the RCIC system, and eventually the system will fail, the reactor core will overheat, the water in the core will boil away, the nuclear fuel in the core will melt, hydrogen gas will accumulate and cause explosions, and radioactive materials will be released into the environment. This is what occurred at Fukushima Daiichi units 2 and 3.
Another scenario SOARCA analyzes is known as a short-term SBO. In this case, DC power is unavailable, operators are not able to use any auxiliary cooling systems, and coolant loss and core melt occur sooner than in the case of the long-term SBO. The event at Fukushima Daiichi unit 1 was essentially a short-term SBO (although because it was a different design than Peach Bottom, the NRC’s analysis is not directly applicable).
The NRC report also evaluated the possibility that operators might be able to use additional mitigative measures to compensate for the loss of all normal sources of AC and DC power. These measures include emergency diesel generators, diesel-driven firewater pumps, and procedures to manually operate the RCIC system and containment venting system without batteries available to power valves and instrumentation. These measures, often called B.5.b measures, were introduced after the 9/11 attacks raised questions about the ability of nuclear plants to recover from the loss of large areas of the plant due to fires and explosions resulting from a malevolent aircraft attack.
However, information revealed by UCS and by the NRC over the last several months has called into question the feasibility and efficacy of these B.5.b measures. So these cannot be assumed to help.
In the long-term SBO analysis with no mitigative measures assumed, the NRC finds that the water level in the reactor core will drop below the top of the nuclear fuel 9 hours after the total loss of power occurs, and the core will be completely uncovered at 11.6 hours. At 19 hours, the nuclear fuel in the core will have completely melted and dropped to the bottom of the reactor vessel, and 30 minutes later the molten fuel will have melted through the reactor vessel and leaked onto the floor of the containment.
The model predicts that hydrogen generated by the reaction of steam with the overheated zirconium alloy encasing the uranium fuel will cause explosions in the reactor building soon after that. These explosions and other phenomena will cause containment failure and significant radiological releases to the environment after 20 hours. (The model predicts that roughly 2% of the cesium and 4% of the iodine in the reactor core is ultimately released to the environment.)
The NRC study assumed that 99.5% of the population within the 10-mile emergency planning zone around Peach Bottom is evacuated within 5 hours and 15 minutes after notification of the accident, and that 50% took potassium iodide tablets. The study also optimistically (and unrealistically) assumed that 20% of the public within 10 to 20 miles away also evacuate within that same time period, even though, as the report admits, “there is no warning or the notification for the public residing in this area, which is not under an evacuation order.”
These two assumptions mean that in the SOARCA study much of the population within 20 miles of the reactor had evacuated long before any radiological releases occurred at the plant. With these assumptions, the study predicts that the average risk to the public within 50 miles of the plant of contracting a fatal cancer is 70 per million. Combining this with the results of a recent report by the Associated Press that found that the population within 50 miles of the Peach Bottom plant is 5.5 million, the NRC predicts that 385 cancer deaths would occur among this population. Much of the radiation exposure causing these illnesses results from long-term occupation of areas that are contaminated but would still be habitable under Pennsylvania laws.
If the people within 20 miles had not finished evacuating in this time, the number of projected cancer deaths could have been larger, as some of the evacuating people could have been exposed to the plume.
This can be seen from the analysis of the of the short-term SBO, in which radiological releases are predicted to occur after about 8 hours, and are somewhat higher than for the long-term SBO (2.3% of the cesium inventory and 10% of the iodine inventory). However, due to the rapid evacuation assumed, even in this case the consequences to nearby residents are limited. Still, the study finds the average cancer fatality risk among the 50-mile population in this case is 160 per million; for a population of 5.5 million, this corresponds to 880 cancer deaths, with a greater proportion due to exposure during the early phase of the accident than in the case of the long-term SBO.
The report goes on to note that the result it obtains for the short-term SBO, 160 deaths per million, is only about a factor of 3 smaller than the worst-case result obtained by the using the worst-case radiological release characteristics of the 1982 Sandia CRAC2 study, even though the CRAC2 worst-case was for a much more serious accident that resulted in a much larger radiological release occurring much sooner (and before most of the population in the 10-mile zone was able to evacuate).
Given the very large uncertainties associated with these kinds of analyses, a factor of 3 difference is not meaningful. Also, this is not a true apples-to-apples comparison, because SOARCA did not even do its own analysis of the type of event represented by the worse case in CRAC2, which was a large-break loss of coolant accident with early containment failure. If SOARCA had done such an analysis, it would have found more severe consequences than its analysis for short-term SBO, and the difference between the SOARCA and CRAC2 worst case would have been even smaller. Thus the SOARCA study, which was intended to show that the CRAC2 results were unrealistically high, has instead essentially confirmed the CRAC2 results.
It’s important to note that the NRC’s results in the SOARCA study are averaged over a large number of different weather conditions. The actual number of cancer deaths resulting from such an accident could be much greater for unfavorable meteorology. The computer codes used by NRC to conduct these analyses typically show that the worst-case results are 10 times the average value, or even larger.
In fact, when the CRAC2 study was first released, it only provided the average values of the results of the health consequences of accidents at U.S. reactors. However, Congressman Ed Markey of Massachusetts obtained and (together with UCS) released a file containing the worst-case results obtained by the Sandia analyses, which did not appear in the NRC report. The fact that the worst-case results were much higher than the average results caused quite a scandal at the time (see, eg, “Nuclear Study Raises Estimates Of Accident Tolls,” Washington Post, Nov. 1, 1982).
For instance, the CRAC2 average number of latent cancer deaths within 500 miles for Peach Bottom was 2,800, but the peak number turned out to be 37,000—thirteen times greater. A similar factor will likely apply to the SOARCA study’s results, so that one might expect as many as 10,000 cancer deaths within 50 miles from the short-term SBO. But just as in the days of CRAC2, the NRC has not provided the maximum values of its analyses.
In summary, the NRC has just spent more than five years and likely a considerable sum of money to essentially reconfirm the validity of the radiological consequence analyses it has been carrying out since the 1980s. This should be a disappointment to nuclear power advocates who were expecting the study to show that the public health consequences of severe accidents were far less than previous studies had indicated. And in fact, the Fukushima accident has provided a real-world demonstration of how large a radioactive release such accidents can cause.
In responding to the UCS FOIA request, the NRC posted the draft SOARCA report on July 14, 2011. It appears in three parts:
The NYT posted a story about this study today.