ML19282C701
| ML19282C701 | |
| Person / Time | |
|---|---|
| Issue date: | 03/15/1979 |
| From: | Hendrie J NRC COMMISSION (OCM) |
| To: | Ertel A, Goodling W HOUSE OF REP. |
| References | |
| NUDOCS 7904040019 | |
| Download: ML19282C701 (3) | |
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UNITED STATES
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March 15, 1979
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CHAIRMAN The Honorable William Goodling United States House of Representatives Washington, D. C.
20515
Dear Congressman Goodling:
Thank you for your letter of February 9,1979 raising questions con-cerning nuclear reactor safety in light of the recent critique of the Reactor Safety Study (WASH-1400) by a review group appointed by the Commission and the Commission's acceptance of the review group's findings.
The NRC established the Risk Assessment Review Group in July,1977 under the leadership of Dr. Harold Lewis, Chairman of the American Physical Society's Study Group on Light Water Reactors.
The review group's charter was to provide advice and information to the Commission regarding WASH-1400, advice and recommendations of risk assessment methodology and recommendations on future courses of action to improve the methodology and its application.
The review group published its report last September.
After consideration of the review group's findings, the Commission issued a policy statement on January 18, 1979 summarizing its response to those findings.
Copies of this policy statement and the report of the review group are enclosed.
As you may know, subsequent to the transmittal of your letter, the Sub-committee on Energy and Environment of the House Committee on Interior and Insular Affairs held a hearing on February 26 concerning the use of the Reactor Safety Study, the effects of NRC's recent adoption of the findings of the Lewis Group, and the safety of licensed nuclear power plants.
Some of the key points made in my testimony at that hearing are sunmarized below.
I am also enclosing a copy of my testimony which provides further details.
In light of the questions raised by you and Mr. Ertel concerning reactor safety, I believe it is important to place in proper perspective the Reactor Safety Study (WASH-1400).
A primary goal of the RSS, as established in 1972, was to obtain a "quantitive evaluation of the risk from the operation of a nuclear plant." The Safety Study was, in effect, a
" measurement," made by analyzing two typical plant designs, of the effectiveness of an existing system of nuclear regulation.
79040400M
The Honorable W.11iam Goodling The regulatory system depends on aving nuclear plants sited, designed, constructed, and operated on the basis of conservative application of sound and accepted engineering principles, on requirements for cultiple and redundant safety systems, and on a set of regulatory requirements that are updated to reflect operating experience.
The designers, builders, and operators of these plants are required to have effective quality assurance programs and their work is subjected to a continuing licensing and inspection process by the NRC.
The results of the li-censing and inspection process are, in turn, subject to independent review by the Advisory Committee on Reactor Safeguards and of ten to examination in public hearings.
This health and safety regulatory system, much of which evolved long before the Reactor Safety Study was carried out, is unchanged in its basic principles today.
It does not depend on the ability to make precise quantitative estimates of overall risk -- although that ability would be highly useful and should ee developed.
We believe this regulatory system nas served us well.
It is an ex-ceptionally rigorous system, and appropriately so in view of the tech-nology we regulate.
It is our job as regulators to make sure that there is no undue risk from licensed facilities and, while one must acknowledge strongly held views to the contrary, over 400 reactor-years of experience to date give us reason to believe that we are on the right track.
Your letter asks what actions the Commission has taken, particularly with regard to the continued operation of 16 nuclear power plants identified by the Union of Concerned Scientists (UCS), to assure the protection of the public in light of the findings of the Lewis Report and the Commission's January 18 policy statement.
Following publication of the review group's findings, the Commission asked Mr. Harold R. Denton, Director, Office of Nuclear Reactor Regulation, to review the extent to which licensing or other regulatory actions relied upon WASH-1400.
Mr. Denton recently reported the results of the NRC staff review to the Commission.
A copy of his report is enclosed.
In his report, Mr. Denton stated that he has "found no actions which, because of their reliance on RSS, should now be overturned." He noted "the record as a whole as showing an ancillary use of the RSS in licensing actions.
Its principal application has been to supplement or confirm the mainstream of analyses and judgments reached by the staff."
The Honorable William Goodling Special attention was given to the issues raised by the UCS in its press release of January 26, 1979 and referenced in your letter.
In his report Mr. Denton states the NRC staff conclusion that "the record has been.aischaracterized by the UCS and that the UCS recommendations to require the shutdown of a number of operating facilities are not warranted."
The staff's views are provided in an Append!x to Enclosure 1 of Mr.
Denton's report.
The Commission is currently reviewing the staff findings.
Your letter also asks what risks we are encountering that we did not know about prior to the Lewis study.
The review group was established to study the present state of risk assessment methodology and to clarify the achievements and limitations of WASH-1400.
It did not identify any new or previously unknown risks per se.
What the Lewis Group has told us is that the " measurement" of our regulatory system, as reflected in the overall risk estimates of the Reactor Safety Study, is much less precise than had been asserted. The Lewis Group did not conclude that the overall risk estimates were higher or lower than reported in WASH-1400, although they speculated on possible factors in both directions, but only that they thought the error bands on those estimates were substantially larger than had been reported.
On that account, they recommended to us that the overall risk estimates of WASH-1400 should be used with great caution - "should not be used uncritically" were their words -- in the regulatory process or for public policy purposes.
We have accepted and are implementing with vigor that reconmendation, as well as the other findings and recommendations of the Lewis Group.
With respect to your third question, concerning the consequences resulting from a shut down of any of the 16 plants for the supply of energy to the affected area, I ha,e asked the NRC staff to review the most recent reserve margins for the utilities involved and will provide separately an answer as soon as it is available.
Finally, you ask how will the NRC deal with the types of safety issues raised by the Lewis study and what, if any, improved safety precautions are needed in existing power plants.
I have already mentioned the review of licensing and other regulatory actions that relied on WASH-1400 undertaken by the NRC staff.
The staff findings and recommendations are contained in the Denton report now under consideration by the Commission.
We will keep you advised of any actions that the Commission deems necessary as a result of this review.
The Honorable William Goodling In addition, the Commission has provided detailed instructions to the NRC staff concerning continued use of risk assessment techniques and results in response to the specific comments of the Risk Assessment Review Group and has as.ked the staff to submit by June 30, 1979, detailed procedures to ensure the proper and effective use of risk assessment theory, methods, data development, and statistical analyses.
In conclusion, I believe it is important to keep in mind what the Commission did and did not do in response to the Lewis report.
It did reevaluate its reliance on, and relationship to, the Reactor Safety Study. However, it did not thereby take a new view of reactor safety.
Nor did the Commission take a new view of past licensing decisions that each licensed plant will be so operated as to provide adequate protection to the health and safety of the public.
I' Sincerely, UL gLds E iloseph M. Hendrie
Enclosures:
As stated
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NUCLEAR REGULATORY COMMISSION gg- 'g WASHINGTON, D. C. 20555 M
March 15, 1979
+....
CHAIRMAN The Honorable Allen Ertel United States House of Representatives Washington, D.C.
20515
Dear Congressman Ertel:
Thank you for your letter 01 w oary 9, 1979 raising questions con-cerning nuclear reactar safety in light of the recent critique of the Reactor Safety Study (WASH-1400) by a review group appointed by the Comission and the Commission's acceptance of the review group's findings.
The NRC established the Risk Assessment Review Group in July, 1977 under the leadership of Dr. Harold Lewis, Chairman of the American iysical Society's Study Group on Light Water Reactors.
The review group's charter was to provide advice and information to the Commission regarding WASH-1400, advice and recomendations of risk assessment methodology and recommendations on future courses of action to improve the methodology and its application. The review group published its report last September.
After consideration of the review group's findings, the Commission issued a policy statement on January 18, 1979 summarizing its response to those findings.
Copies of this policy statement and the report of the review group are enclosed.
As you may know, subsequent to the transmittal of your letter, the Sub-committee on Energy and Environment of the House Committee on Interior and Insular Affairs held a hearing on February 26 concerning the use of the Rcactor Safety Study, the effects of NRC's reunt adoption of the findings of the Lewis Group, and the safety of licensed nuclear power plants.
Some of the key points made in my testimony at that hearing are summarized below.
I am also enclosing a copy of my testimony which provides further details.
In light of the questions raised by you and Mr. Goodling concerning reactor safety, I believe it is important to place in proper perspective thf Reactor Safety Study (WASH-1400). A primary goal of the RSS, as established in 1972, was to obtain a "quantitive evaluation of the risk from the operation of a nuclear plant." The Safety Study was, in effect, a " measurement," made by analyzing two typical plant designs, of the effectiveness vi an existing system of nuclear regulation.
The Honorable Allen Ertel The regulatory system depends on having nuclear plants sited, designed, constructed, and operated on the basis of conservative application of sound and accepted engineering principles, on requirements for multiple and redundant safety systens, and on a set of regulatory requirements that are updated to reflect operating experience.
The designers, builders, and operators of these plants are required to have effective quality assurance programs and their work is subjected to a continuing licensing and inspection process by the NRC.
The results of the licensing and inspection p-ocess are, in turn, subject to independent review by the Advisory Committee on Reactor Safeguards and often to examination in public hearings.
This health and safety regulatory system, much of which evolved long before the Reactor Safety Study was carried out, is unchanged ir its basic principles today.
It does not depend on the ability to make precise quantitative estimates of overall risk -- although that ability would be highly useful and should be developed.
We believe this regulatory system has served us well.
It is an ex-ceptionally rigorous system, and appropriately so in view of the tech-nology we regulate.
It is our job as regulators to make sure that there is no undue risk from licensed facilities and, while one must acknowledge strongly held views to the contrary, over 400 reactar-years of experience to date give us reason to believe that we are on the right track.
Your letter asks what actions the Commission has taken, particularly with regard to the continued operation of 16 nuclear power plants identified by the Union of Concerned Scientists (UCS), to assure the protection of the public in light of the findings of the Lewis Report and the Commission's January 18 policy statement.
Following publication of the review group's findings, the Commission asked Mr. Harold R. Denton, Director, Office of Nuclear Reactor Regulation, to review the extent to which licensing or other regulatory accions relied upon WASH-1400.
Mr. Denton recently repcrted the results of the NRC staff review to the Commission.
A copy of his report is enclosed.
In his report, Mr. Denton stated that he has "found no actions which, because of their reliance on RSS, should now be overturned." He noted "the record as a whole as showing an ancillary use of the RSS in licensing actions.
Its principal application has been to supplement or confirm the mainstream of analyses and judgments reached by the staff."
The Honorable Allen Ertel Special attention was given to the issues raised by the UCS in its press release of January 26, 1979 and referenced in your letter.
In his report Mr. Denton states the NP,C staff conclusion that "the record has been mischaracterized by the UCS and that the UCS recom endations to require the shutdown of a number of operating facilities are not warranted."
The staff's views are provided in an Appendix to Enclosure 1 of Mr.
Denton's report.
The Commission is currently reviewing the staff findings.
Your letter also asks what risks we are encountering that we did not know about prior to the Lewis study.
The review group was established to study the present state of risk assessment methodology and to clarify the achievements and limitations of WASH-1400.
It did not identify any new or previously unknown risks per se.
What the Lewis Group has told us is that the " measurement" of our regulatory system, as reflected in the overall risk estimates of the Reactor Safety Study, is much less precise than had been asserted.
The Lewis Group did not conclude that the overall risk estimates were higher or lower than reported in WASH-1400, although they speculated on possible factors in both directions, but only that they thought the error bands on those estimates were substantially larger than had been reported.
On that account, they recommended to us that the overall risk estimates of WASH-1400 should be used with great caution -
"should not bc used uncritically" were their words -- in the regulatory process or for public policy purposes. We have accepted and are implementing with vigor that recommendation, as well as the other findings and recommendations of the Lewis Group.
With respect to your. third question, conceriting the consequences resulting from a shut down of any of the 16 plants for the supply of energy to the affected arca, I have asked the NRC staff to review the most recent reserve margins for the utilities involved and will provide separately an answer as soon as it is available.
Finally, you ask how will the NRC deal with the types of safety issues raised by the Lewis study and what, if any, improved safety precautions are needed in existing power plants.
I have aircady mentioned the review of licensing and other regulatory actions that relied on WASH-1400 undertaken by the NRC staff.
The staff findings and recommendations are contained in the Denton report now under consideration by the Commission. We will keep you advised of any actions that the Commission deems necessary as a result of this review.
The Honorable Allen Ertel In addition, the Commission has provided detailed instructions to the flRC staff concerning continued use of risk assessment techniques and results in response to the specific comments of the 9.isk Assessment Review Group and has asked the staff to submit by June 30, 1979, detailed procedures to ensure the proper and effective use of risk assessment theory, methods, data development, and statistical analyses.
In conclusion, I believe it is important to keep in mind what the Conmission did and did not do in response to the Lewis report.
It did reevaluate its reliance on, and relationship to, the 'leactor Safety Study.
However, it did not thereby take a new view of reactor safety.
flor did the Commission take a new view of past licensing decisions that each licensed plant will be so operated as to provide adequate protection to the health and safety of the public.
(4 Sincerely, (L \\ LtSA.
Jos_eph M. Hendrie
Enclosures:
As stated
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Construction and Operation Appendix B to 10 CFR Part 50 of the NRC regulations establishes mandatory quality assurance criteria for all phases of nuclear power plant design, construction, and operation. These criteria are implemented by field reviews and inspection by the NRC staff.
Each license for operation of a nuclear reactor contains Technical Specifications, which set forth the particular safety and environmental protection measures to be imposed upon the plant, and the operating conditions that are to be met in order to assure protection of the health and safety of the public and of the surrounding environment.
The NRC's Office of Inspection and Enforcement continues its inspections during the operating life of the plant to ensure that the requirements of NRC's licenses are enforced, that problems arising in operation are well handled, and that valuable feedback from operating experience is made available to other licensees and incorporated into the safety reviews of other plants.
Furthermore, NRC liron os require utilities to test important safety systems periodically snJ to report failures of all safety-related equipment to the NRC.
I should note that we have some steps underway to improve this process of getting operating experience and testing information out to other licensees.
The results of NRC inspections and reports of equipment failures are routinely made public.
The continuing review of operating experience by licensees and by the HRC staff provides another important contribution to the a.isurance of nuclear power plant safety.
Design improvements, based on this experience, can be incorporated into new plants, and any mistakes in design and construction of operating plants can be corrected.
Even after nuclear plants begin commercial operation, they are not insulated from safety improvements.
There has been a continuing NRC program of improvements in 1xisting nuclear power plants, based on cperating experience, new criteria, and better understanding of safety issues through research, testing and analysis. As the number of operating nuclear power plants has increased over the years, there has been a corresponding increase in the allocation of NRC staff resources to the inspection program and to the technical safety evaluation efforts necessary to provide continued assurance of safe operation of licensed reactors.
One of the many examples of the feedback of operating experience to upgrading of safety requirements involves fire protection.
After the Browns Ferry fire in March 1975, an NRC Special Review Group was establisl.ad to identify the lessons learned from this event and to make recommendations for the future.
As a result,
. the Commission's Office of Inspection and Enforcement issued bulletins to licensees and initiated special fire protection inspections.
In response, licensees instituted a number of immediate improvements in fire protection at their plants. A generic task activity was initiated by the staff to develop upgraded guidelines for fire protection in nuclear power plants.
The generic task culminated in mid-1976 with the issuance of a revised Standard Review Plan section on fire protection. At that time we started a re-evaluation of each operating reactor against the new guidelines and we are requiring appropriate plant modi-fications to upgrade fire protection.
The new guidelines have been used as a basis for fire protection review for all operating license and construction permit applications under review since mid-1976.
In summary, the NRC recognizes that the operation of nuclear power plants presents some element of risk.
But we believe that our process, which involves a well-developed safety approach, the specification of safety design requirements to implement that approach, and an extensive safety review, licensing and inspection process, gives reasonable assurance that that risk is comparatively very small.
. The safety record so far achieved in the operation of nuclear power plants gives support to the validity of the NRC approach. We have had, at this point, approximately 440 reactor-years of operation of licensed commer:ial nuclear plants in the United States without an accident having significant effect on the health and safety of the public. While this experience is, of course, much less than that needed to prove our belief that large reactor accidents have a low probability of occurrence, it is an encouraging record and an outstanding one for a major industrial activity.
NRC's regulatory process has relied and will continue to rely on the
,iudgment of highly skilled engineers and scientists as the source for its safety decisions.
Based on the aforementioned considerations, and without prejudice to any conclusion we might reach in any individual licensing proceeding, we believe that nuclear power plants designed, constructed, licensed to operate, and operated in accordance with our regulations and requirements present no undue risk to the public.
It would be nice to be able to say that there are absolutely no problems with respect to the safety of nuclear power plants, that perfection has
. been achieved, and that all risks have been eliminated. This is not the case.
While we believe that nuclear power plants are adequately safe, in tha ordinary sense of the word, and that the risk to the public health and safety from their operation is very small, the Commission's intention is to assure that this risk remains very small so that nuclear power can continue to represent a suitable and safe alternative for satisfying a portion of the nation's electrical energy needs.
The Reactor Safety Study (WASH-1400)
The c,'iestion of risk from reactor accidents is not new one, and I should like now to talk about how the Reactor Safety Study (WASH-1400) and the subsequent Risk Assessment Review Group came about.
In 1971, Senator Pastore, Chairman of the Joint Committee on Atomic Energy wrote to the Chairman of the Atomic Energy Commission, urging that a study be undertaken which would allow the AEC to document in clear terms the levels of safety it deemed necessary in nuclear power plants as well as the levels of safety that were actually present in current design. To quote from the appendix to the Pastore letter, "One way of accomplishing this objective would be to prepare a report which, by addressing the probability of occurrence and consequences of the spectrum of accidents which could befall a nuclear power plant, would represent an assessment of the risks involved in the use of nuclear plants. Of course, it would also be necessary to compare
. these risks with those involved in other fields of endeavor in our society in order to put them into proper perspective."
In August, 1972, the Chairman of the Atomic Energy Commission informed the Chairman of the Joint Committee on Atomic Energy that the Atomic Energy Commission had undertaken an in-house study "to provide a basis for submitting recommendations to the Congress regarding the, extension or modification of the Price-Anderson Act."
The Reactor Safety Study -- WASH-1400 -- thus was sponsored by the Atomic Energy Commission to estimate the public risks that could be involved in potential accidents in commercial nuclear power plants.
It was performed under the independent direction of Professor Norman C. Rasmussen of the flassachusetts Institute of Technology, and soon became known as the "Rasmussen Report." The study was done principally at AEC headquarters by a group of scientists and engineers drawn from the AEC, the national laboratories, and universities. The study was started in the summer of 1972 and took three years to complete. A total of 60 people, various consultants, 70 man-years of effort, and about four million dollars were involved.
The study's objective was to make a realistic estimate of risks associated with nuclear power plants, and to provide perspective, to compare them with non-nuclear risks to which our society and its individuals are already exposed.
The study used fault tree and event tree methodologies to define potential accident paths and their likelihood of occurrence.
Its focus was limited to large power reactors of the pressurized water and boiling water types, as represented by two specific units, one of each type. These two units were completed reactors, so that the study could deal with the final designs and the as-built plant features.
These units were designed to the safety criteria of the 1966-72 period.
The massive study was released in draft form in August of 1974, and comments were requested from environmental groups, groups critical of nuclear power, lawyers representing environmental groups and industry, government agencies, and industrial organizations representing reactor manufacturers, architect-engineerina firms, and electric utilities.
About 90 organizations and individuals responded with comments totaling about 1800 pages.
The primary focus of criticism'of the Reactor Safety Study related to the numerical estimates of risk and the range of uncertainties attributed to them.
Both the probability estimates and the consequence estimates were subjects of controversy.
In addition, there was considerable and continuing criticism of the manner in which the peer-group review was handled by the study's authors The Executive Summary of WASH-1400 also came in for criticism as being presented to provide a favorable picture of the risks associated with commercially-generated nuclear power.
The Risk Assessment Review Group Cognizant of these criticisms, and at the particular behest of yourself, Mr. Chairman, the NRC organized a Risk Assessment Review Group on July 1, 1977.
It was charged with four responsibilities:
-- to clarify the achievements and limitations of WASH-1400;
-- to assess the peer comments thereon, and responses to those comments;
-- to study the present state of such risk assessment methodology;
-- and to recommend to the Comission how (and whether) such methodology can be used in the regulatory and licensing process.
The Risk Assessment Review Group was chaired by Professor Harold Lewis of the University of California at Santa Barbara, and its findings have became known as the " Lewis Report." The findings were published in September 1978 as NUREG/CR-0400. As the Committee was provided with copies of the report as soon as it was published, I will not go into extensive detail regarding the findings, which I am sure are familiar to all of you.
The Lewis Report did come down very hard on three of the most-criticized aspects of WASH-1400 -- the risk estimates, the Executive Summary and the peer group review. To quote directly from the Findings and the Summary:
"We are unable to determine whether the absolute probabilities of accident sequences in WASH-1400 are high or low, but we believe that the error bounds on those estimates are, in general, greatly understated. This is true in part because there is in many cases an inadequate data base, in part because of an inability to quantify common cause failares, and in part because of some questionable methodological and statistical procedures."
"Among our other findings are the well-known one that WASH-1400 is inscrutable, and that it is very difficult to follow the detailed thread of any cal:ulation through the report. This has made peer review very difficult, yet peer review is the best method of assuring the technical credibility of such a complex undertaking.
In particular, we find that the Executive Summary is a poor description of the contents of the Report, should not be portrayed as such, and has lent itself to misuse in the discussion of reactor risks."
On the positive side. one of the important findings of the Lewis Report is that:
"Despite its shortcomings, WASH-1400 provides at this time the most complete single picture of accident probabilities associated with nuclear reactors. The fault-tree / event-2e approach coupled with an adequate data base is the best available tool with which to quantify these probabilities."
Commission Response After extensive deliberation, the Commission issued on January 18 a policy statement concerning the Lewis Report, in which it accepted the findings of the Lewis group and re-examined its views on WASH-1400 as a result of their report. Copies of this policy statement and of the Commission's instructions to the staff as to actions to be taken regarding the Review Group Report have been provided to the Committee, and are also appended to this statement.
I will not repeat the policy statement here.
Rather, I would like to make a comment on the relatior of WASH-1400 and the Lewis Report to our regulatory process.
A primary goal of the Reactor Safety Study was to obtain "a quantitative evaluation of the risk from the operation of a nuclear plant." The Safety Study was, in effect, a " measurement," made by analyzing two typical plant designs, of the results of our system of nuclear regulation.
What the Lewis group has told us is that the " measurement" of these results of our regulatory system, as reflected in the overall risk estimates of the Reactor Safety Study, is much less precise than had been asserted. The Lewis group did not conclude that the overall risk estimates were higher or lower than reported in WASH-1400, although they speculated on possible factors in both directions, but only that they thought the error bounds on those estimates were substantially larger than had been reported.
On that account, they recommended to us that the overall risk estimates of WASH-1400 should be used with great caution - "should not be used uncritically" were their words -- in the regulatory process or for public policy purposes. We have accented and are implementing with vigor that recommendation, as well as the other findings and recommendations of the Lewis group.
. I should like to emphasize that our regulatory system, much of which evolved long before the Reactor Safety Study was carried out, does not depend on the ability to make precise quantitative estimates of overall risk. That ability would be highly useful, and should be developed. but it is not essential to our regulatory system.
Instructions to the Staff 2
The Commission bolstered its January 18 policy statement with instructions to the staff that I can paraphrase as follows:
-- review the extent to which past and pending licensing or other regulatory actions have relied on the risk assessment models and estimates of the Reactor Safety Study;
-- give special attention to those activities identified by the Review Group as being especially amenable to risk assessment, such as generic safety issues or new regulatory requirements, assessing and revalidating existing regulatory requfrements, evaluating new designs, and formulating reactor safety research and inspection ~ priorities;
-- prepare and submit by June 30, 1979 detailed procedures to ensure the proper and effective use of risk assessment theory, methods, data development, and statistical analyses by the staff;
-- prepare a review of current NRC practices and procedures in two areas of particular concern to the Review Group: the peer review process for risk assessment developments, and the coordinatinn among the research and probabilistic dnalysis staff and the licensing and regulatory staff in order to promote the effective use of these techniques;
-- follow Commission-defined procedures in the use of risk assessment techniques during the licensing process; such use is encouraged with full cognizance of the comments of
.the Lewis Report; and
-- send copies of the Risk Assessment Review Group Report and Commission policy statement to all known recipients of the Reactor Safety Study.
The Commission stated that it would make whatever changes are nccessary to assure that effective peer review and interoffice coordination are integral features of NRC's risk assessment program.
Finally, the Commission directed the staff to examine the significance of the technical issues raised by the Review Group and the appropriate courses of action for dealing with them.
The Commission noted that it will address changes that should be proposed in the approved FY 1979 and FY 1980 research program to improve the data base, including that on human behavior.
. Staff Actions to Date The staff has begun the Commission-directed review of the extent to which past and pending licensing or other regulatory actions have relied on risk assessment models and estimates of the Reactor Safety Study. A preliminary survey, completed in December, identified many instances where the Reactor Safety Study was mentioned or discussed, but only a few where the staff considered that the RSS played a substantial role in the licensing process.
In general, the survey revealed no general disposition toward primary reliance on the RSS, with only three items identified as warranting reconsideration:
some aspects of the Clinch River application, a staff report on anticipated transients..without scram (ATWS), and d.c. power supply reliability.
The survey also revea-led a-wice-range of opinion on the RSS within NRC.
Some staff members were very critical of the RSS, while others found the benefits of the RSS greatly to outweiah its flaws.
Because of the subjective factors involved in staff use of the RSS, the review was more carefully refined.
The Director of Nuclear Reactor Regulation and his Division Directors met with individuals responsible for those documents which appeared to involve at least partial reliance on the RSS in justifying either the status quo or a relaxation of requirements. Approximately 40 cases were reviewed. The discussions focused on the role that the RSS actually played in the anaylsis, whether its use was a determinative factor in the decision, and whether a different conclusion would have been reached today.
Once again, the survey team found no pattern indicating significant dependence on the RSS for licensing decisions.
Four additional instances were identified where the staff's use of the RSS would not now be in con-formance with the Commission's recent guidance, although primary reliance was not placed on WASH-1400.
Future actions on these matters will reflect the new guidelines.
Reviews of correspondence did reveal numerous references to WASH-1400 estimates of failure rates, principally the probability of a pipe break or a large loss of coolant accident.
The written record generally does not contain a discussion of the uncertainties associated with those estimates, but discussions with the responsible individuals indicate that these uncertainties were considered by the staff and were an element of the decision-making process, albeit an implicit one. The Director of Nuclear Reactor Regulation will provide specific guidelines to assure the explicit treatment of uncertainties in the future.
In summary, a preliminary view of the use of WASH '400 in licensing actions indicates that its principal application has been to supplement or confirm the main stream of analyses and judgments ~ reached by the staff.
Past and present regulatory decisions depended on traditional engineering analyses rather than any assumed finality of the RSS. When the final report on these reviews is prepared and documented and the Commission has reviewed it, we will forward it to you.
Where Do We Go From Here?
The Risk Assessment Review Group raised a series of technical issues that will have to be examined and dealt with by the stari.
These issues include questions about statistical methods, the availability and quality of data bases, consequence modeling, human factor consid-erations, earthquakes, fires, and common cause failures.
Work is already undenvay on all of these matters as part of our confirmatory research program, and we will soon be considering what additional efforts are needed in order to address all of the areas requiring improvement in WASH-1400.
Because there is a substantial amount of work to be done in improving the data and the methods, I do not believe it would be desirable to launch another full-blown Reactor Safety Study at this point.
Those improvements need to be in hanu and agreed to before we will be in cood shape to reduce significantly the uncertainties in the predicted values of overall risk. I believe that this effort will take three or four years to accomplish. However, there are some useful parts of the effort that can be done in shorter time.
For example, we have been making studies of the consequence model to determine the sensitivity of its predictions to various meteorolooical factors such as rain, plume rise, and wind shear, to the correlation between wind direction and population, and to evacuation modeling assumptions. We would be able, within the coming year,to produce an updated risk curve that would indicate the impacts of these sensitivity explorations with the consequence model.
Beyond that, we will be examining the possibility, and also considering the usefullness and the resources required, of a program of periodic updating of the RSS overall risk curves to indicate the effects of various additional modeling improvements that we will be making.
This type of effort would help to answer various criticisms that have been made of the RSS and put us in better posture to be raady for a more complete update of the RSS after several years.
By taking this step-by-step route, we could gradually reduce the uncertainties in RSS-type risk predictions.
In conclusion, I think it is important to keep in mind what the Commission did,1d did not do in response to the Lewis Report.
It did reevaluate its reliance on, and relationship to, the Reactor Safety Study.
But it did not thereby take a new view of reactor safety.. I continue to
talieve that our licensing proceedings, standards, and requirements are such that each licensed nuclear power plant is constiucted and operated so as to provide adecuate protection to the health and sataty of the public.
Thank you Mr. Chairman.
I think you may want to hear from my colleagues now.
ATTACHMENT 1 January 18, 1979 NRC STATEMENT ON RISK ASSESSMENT AND THE REACTOR SAFETY STUDY REPORT (WASH-1400)
IN LIGHT OF THE RISPs ASSESSMENT REVIEW GROUP REPORT The Risk Assessment Review Group, chartered by the NRC in July,1977 to " provide advice and information to the Comission on the final report of the Reactor Safety Study, WASH-1400," and related matters, y submitted its report te the Comission on September 7,1978.
The Review Group, chaired bi Professor Harold Lewis of the University of California at Santa Barbara, 2/ was formed in response to letters from Congressman Udall, Chairman of the House Comittee on Interior and Insular Affairs, expressing misgivings about the Reactor Safety Study (WASH-1400), and in particular about the " Executive Sumary" published with the Main Report.
It was expected that the Review Group's report would " assist the Comission in establishing policy regarding the use of risk assessment in the regulatory process" and that it would " clarify the achievements and limitations of the Reactor Safety Study."
In August,1972, the Chairman of the Atomic Energy Comission informed the Chairman of the Joint Comittee on Atomic Energy that the Atomic Energy Commission had undertaken an in-house study "to provide a basis for submitting recomendations to the Congress regarding the extension or modification of the Price-Anderson Act."
A draft version of the study report was circulated for coment in April,1974.
On October 30, 1975, the Nuclear Regulatory Commission 3f announced that the final report had been completed.
Criticism of the document following release centered on the method of treating peer coments on the draft report as well as on the substance of the report.
The NRC p'tess release accompanying publication of WASH-1400 praised the report, describing it as a " realistic assessment..., providing an objective and meaningful estimate of the present risks associated with the operation of present day light water reactors in the United States," gave several comparisons to show that the risk from nuclear power was much less than from other man-made activities, and included a statement that "the final report is a soundl'y based and impressive work....
Its overall conclusion is that
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the risk attached to the operation of nuclear power plants is very low compared with other natural and man-made risks." 4/
In view of the importance attached to the Reactor Safety Study, within and outside the Commission, both prospectively and after it was made public, the Comission has reexamined it's views regarding the Study,in light of the Review Group's critique.
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. While praising the study's general methodology and recognizing its contribution to assessing the risks of nuclear power, the Review Group was critical of the Executive Summary, the precedure followed in producing the final report and the calculations in the body of the. report.
Among the major failings of the study, the Review Group cited:
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The executive Summary:
The Review Group concluded that "the Executive Summary of the RSS is a poor description of the 5
content's of the report, should not be portrayed as such, and 1
has lent itself to misuse in the discussion of reactor risks."
The Review Group indicated the Executive Summary does not adequately indicate the full extent of the consequences of.
reactor accidents and does not sufficiently emphasize the uncertainties involved in the calculations of their probability.
As a result, the reader may be left with a misplaced confidence in the validity of the risk estimates and a more favorable impression of reactor risks in comparison with other risks than warranted by thestudy.5/
The Peer Review Process:
The Review Group Report criticized the RSS staff response, pointing out that in some cases ' cogent comments from critics either were not acknowledged or were evaded and that, in general, the record of response to valid criticism was weaker than it should ha.e been.
The Report points out-that the lack of clarity of WASH-1400 itself led.to major diffi-culty in tra'cing a line of thought through the study and crippled many efforts to accomplish responsible peer reviews.
Accident Probabilities:
The Review Group was unable to deter-mine whether the absolute probabilities of accident sequences in WASH-1400 are high or low, but believes that the error bounds on those estimates are, in general, greatly understated.
This, the Report said, is true in part because there is in many cases an inadequato data base, in part because of an inability to quantify common cause failures, and in part because of some questionable methodological and statistical procedures.
The Review Group also criticized, in some cases severely, various of the calculational techniques in the Stuuy as well;ts its lack of clarity.
cz The Review Group cited the following as major achievements of the study:
" WASH-1400 was a substantial advance over previous attempts to estimate the risks of the nuclear option.
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. " WASH-1400 was.argely successful in at least three ways; in making the study of reactor safety more rational, in establishing the topology of many accident sequences, and in delineating procedures through which quantitative estimates of the risk can be derived for those sequences for which a data base exists.
"Despite its shortcomings, WASH-1400 provides at this time the most complete single picture of accident probabilities associated with nuclear reactors.
The fault-tree / event-tree approach coupled with an adequate data base is the best available tool with which to quantify these probabilities.
" WASH-1400 made clear the importance to reactor safety dis-cussions of accident consequences other than early fatalities."
The Commission accepts these findings and takes the following etions:
Executive Summary:
The Commission withdraws any explicit or implicit past endorsement of the Executive Summary.
The Peer Review Process:
The Commission agrees that the peer review process followed in publishing WASH-1400 was inadequate and that proper peer review is fundamental to making sound, technical decisions.
lhe Commission will take whatever corrective action is necessary to assure that effective peer review is an integral feature of the NRC's risk assessment program.
Accident probabilities:
The Commission accepts the Review
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Group Report's conclusion that absolute values of the risks presented by WASH-1400 should not be used uncritically either in the regulatory process or for public policy purposes and has taken and will continue to take steps to assure that any such use in the past will be corrected as appropriate.
In particular, in light of the Review Group conclusions on accident probabilities, the Commission does not regard as reliable the Reactor Safety Study's numerical estimate of the overall risk of reactor accident.
Communication with the Congress and the Public:
Commission correspondence and statements invciving WASH-1400 are being re' viewed and corrective action as necessary will be taken.
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'a'ith respect to the component parts of the Study the Commission expects the staff to make use of them as appropriate, that is, where the data base is adequate and analytical techniques permit.
Taking due account of the reservations expressed in the Review Group Report and in its presentation to the Commission, the Commission supports the extended use of probabilistic risk assessment in regulatory decisionmaking.
The Commission has provided additional detailed instructions to the NRC
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staff concerning continued use of risk assessment techniques and results in response to specific criticisms raised by the Risk Assessment Review Group.
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NOTES
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1/
Its charter reads:
"The Review Group will provide advice and information to the Comission regarding the final report of the Reactor Safety Study, WASH-1400, and the peer coments on the Study, advice and recomendations on developments in the field of risk assessment methodology and on future courses of
. action which should be taken to improve this methodology and its application. This advice and iaformation will assist the Comission in establishing policy regarding the use of risk assessment in the regulatory process, in improving the base for the use of such assessments.
It will also clarify the achieve-ments and limitations of the Reactor Safety Study."
2f The other members were Dr. Robert J. Budnitz (Lawrence Berkeley Laboratory, University of California), Dr. Herbert J. C. Kouts (Brookhaven National Laboratory), Dr. Walter Loewenstei:.
(Electric Power Research Institute), Dr. William Rowe (Environ-mental Protection Agency), Dr. Frank von Hippel (Princeton University) and Dr. Fredrik Zachariasen (California Institute of Technology).
Dr. Budnitz is presently on leave from the University of California and is cerving (since August 1978) as Deputy Director of the NRC's Office of Nuclear Regulatory Research.
3/
The Nuclear Regulatory Comission was established on January 19, 1975 to carry out the regulatory functions of the Atomic Enargy Commission, which was abolished on that date.
4f The press release at the time of publication said that the report is "the culmination of the most comprehensive risk assessment of nuclear power plants made to date.
The objectives of the
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study were to make a realistic assessment....
The overall conclusion...is that the risks attached to the operation of present day nuclear power plants are very low compared to other natural and man-made risks....
Nuclear power plants are abou_t-10,000 times less likely to produce fatal accidents than man-made non-nuclear activities....
Non-nuclear accidents involving comparable large dollar value damage are about 1,000 times more likely than nuclear power plant accidents....
The chance that a person living in the general vicinity of a nuclear power plant will be fatally injured in' a reactor accident is one in five billion per year....
In the event of an unlikely reactor accident with a probability of one in a million per reactor per year, latent health effects except for thyroid nodules would be such a small percentage of the normal incident rates that they would be. difficult to detect...."
The NRC Chairman was quoted as saying, "The Commission believes that the Reactor Safety Study Report provides an objective and meaningful estimate of the public risks associated with the operation of present day -
light water reactors in the United States....
The final report is a soundly based and impressive work....
Its.overall conclusion is that the risk attached to the operation of nuclear power plants is very low compared
. ith other natural and man-made risks." The press w
. release went on to say that more than 1800 pages of comments were received from a broad spectrum of people and all were carefully considered in preparing the final report.
5/
Professor Lewis, in reporting to the Commission, said that the Executive Summary was not a summary of the report.
He concluded it was written as a public statement that reactors were safe compared to other risks to which the public is exposed and he stated it should-not have been attached to the report and described as a part of it.
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ATTACHMENT 2 U. ATED STATES
/pacc A NUCLEAR REGULATORY COMMISSION oq y
g WASHINGTON, D. C. 20555
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January 18, 1979 y...../
OFFICE OF THE SECRETARY MEMORANDUM FOR:
Lee V. Gossick Executive Director for OperaticasQ FROM:
Samuel J. Chilk Secretary of the Commissio 7
SUBJECT:
STAFF ACTIONS REGARDING RI K A ESSMEtiT REVIEW GROUP REPORT Attached is a policy statement issued by the Commission on January 18, 1979.
In addition, the Commission has provided the following instructions for the staff.
1.
Send copies of the Risk Assessment Review Group Report (NUREG/CR-0400) and of the January 18, 1979 Commission policy statement to all known domestic and international recipients of the RSS.
In the future, copies of the RSS Executive Summary and the complete RSS will be distri-buted only when accompanied by a copy of the Review Group's report and a copy of this statement.
2.
Quantitative risk assessment techniques and results can be used in the licensing process if proper consideration is given to the results of the Review Group.
The staff should use the following procedures re-garding the use of quantitative risk assessment techniques and results pending development of further guidance:
a.
In comparisons of risks from nuclear power plants with other risks, the overall risk assessment results of the RSS (i.e., curves or tables of the probability 'of occurrence of various consequences) shall not be used without an indication of the wide range of uncertainty associated with those estimates.
Any such use should note the difficulty of placing high confidence on estimates that are well below the values set by experience.
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. b.
Quantitative risk assessment techniques may be used to estimate the relative importance of potential nuclear power plant accident sequences or other features where sufficient similarity exists so that the comparisons are not invalidated by lack of an adequate data base.
Such techniques should not be used to estimate absolute values of probabilities of failure of subsystems unless an adequate data base exists, and it is possible either to quantify the uncertainties or to support a conservative analysis.
c.
The quantitative estimates of event probabilities in the RSS should not be used as the principal basis for any regu-latory decision.
However, these estimates may be used for relative comparisons of alternative designs or requirements provided that explicit considerations are given to the criti-cisms of those estimates as set forth in the Report of the Risk Assessment Review Group.
d.
The RSS consequence model shall not be used as the basis for licensing decisions regarding individual nuclear power plant sites until significant refinements and sensitivity tests are accomplished.
However, the consequence model may be used for relative comparisons provided that such estimates are not the primary basis for such reviews and provided that explicit consideration is given to the criticisms of the various elements of that model as set forth in the Report of the Risk Assessment Review Group.
The staff shall prepare and submit by June 30, 1979, detailed pro-cedures to ensure the proper and effective use of risk assessment theory, methods, data development and statistical analyses by the staff.
Pending review by the Commission of these detailed procedures and the bases and rationale supporting them, the Office Directors will obtain the advice of the ED0's Regulatory Requirements Review Committee should questions arise regarding the implementation of the above instructions.
3.
The staff shall review the extent to which past and pending li-censing or other regulatory actions, including Commission, ACRS and li-censing board actions and statements, have relied on the risk assessment models and risk estimates of the RSS.
The Commission will examine the results of this review to determine whether the degree of reliance identified was and continues to be justified and to decide whether regulatory modifications are appropriate.
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. 4.
The staff shall give special attention to those activities identified by the Review Group as being especially amenable to risk assessment, i.e., dealing with generic safety issues, formulating new regulatory requirements, assessing and re-validating existing regulatory requirements, evaluating new designs, and formulating reactor safety research and inspection priorities.
5.
The staff shall prepare a review of current NRC practices and pro-cedures in bvo areas of particular concern to the Review Group:
a.
the peer review process for risk assessment developments, and b.
the coordination among the research and probabilistic analysis staff and the licensing and regulatory staff, in order to promote the effective use of these techniques.
The Commission will make whatever changes are necessary to assure that effective peer review and interoffice coordination are integral features of NRC's risk assessment program.
6.
The staff shall examine the significance of the technical issues raised by the Review Group and the appropriate courses of action for dealing with them.
These issues include questions about statistical methods, data base quality and availability, consequence modeling, human factor considerations, earthquakes, fires, and common cause failures.
The Commission will address what changes should be proposed in the approved FY 79 and proposed FY 80 research program to improve the data base, including that on human behavior.
As an addditional action, the staff shall undertake a review of statistical methods and human factor considerations used in riak assessment.
Attachment:
As stated cc:
Chairman Hendrie Commissioner Gilinsky Commissioner Kennedy Commissioner Bradford Commissioner Ahearne James L. Kelley, OGC Kenneth Pedersen, OPE.
Joseph J. Fouchard, OPA Carlton C. Kammerer, OCA
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