ML20056C524
| ML20056C524 | |
| Person / Time | |
|---|---|
| Issue date: | 05/07/1993 |
| From: | Ward D Advisory Committee on Reactor Safeguards |
| To: | Houston D Advisory Committee on Reactor Safeguards |
| References | |
| ACRS-CT-2073, NUDOCS 9306240416 | |
| Download: ML20056C524 (7) | |
Text
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6T-ab 73 pe 6/wlO cc: Tom Kress May 7,1993 To: Dean Houston, ACRS staff From: Dave Ward, ACRS consultant w
Subject:
Memorandum from Heltemes to Larkins,4/19/93, STAFF APPROACH FOR ASSESSING THE CONSISTENCY OF THE PRESENT REGULATIONS WITH RESPECT TO THE COMMISSION'S SAFETY GOALS Your note asked that i provide comments on this subject to you or Tom Kress.
Comments follow:
ACRS has recommended, in several letters over the past few years, that given; Safety Goals are available as a standard, PRA is available as a tool, and IPE, PRA, and ASP results are available as data The Commission should examine its body of regulations and regulatory practice to confirm whether it is doing a good job and to guide improvements in efficiency of regulation. Regulations and practices that do not contribute to helping the population of plants meet the Safety Goal should be dropped, necessary but weak regulations should be strengthened, and regulatory gaps should be filled.
The Commission has instructed the Staff, in two SRMs written in 1990, to do essentially this (at least their instructions can be so interpreted. The Staff has responded that some of its existing programs, three in particu ar, are doing what the SRMs have asked. Therefore, the Staff believes, no additional effort is needed.
I believe existing programs will 0g1 do what the Commission has asked and ACRS has recommended. I've listed below, A through O, specrfic requirements or objectives, relating to the overall task drawn from the SRMs. I have also taken the liberty to include specific objectives that can be deduced from ACRS letters, but which were not clearty included in the SRMs. In some cases, I've paraphrased the objective, but also given its source. Following that, IW tried to summanze what it is that each of the three Staff programs intends to accomplish opposite these requirements and objectives.
Detailed objectives of a program designed to assess regulations against the safety goals - from SRMs and ACRS letters A. "The staff should describe a plan, with specific detail, for assessing the consistency of our regulations with the safety goals..." [SRM of $15/90, item BJ
,y B. "... for identifying and Q
[SRM of 6/15/90, item B] possibly eliminating unnecessary requirements..."
O C. "... modifying requirements that may be inadequate.." [SRM of 6/15/90, item 8]
O D. "... consider whether a trial case of limited scope may be a useful way to proceed...* [SRM of 6/15/90, item 8]
C " N 8AL 930624o416 930507
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2 E. Where the benefit of a new requirement cannot be quantified in risk terms, the staff should elevate the proposal to the Commission for its consideration. [SRM of W15/90, item 9]
F. Routinely consider the Safety Goals in developing and reviewing regulations and regulatory practices. [SRM of 6/15/90, item 3]
G. Establish a formal mechanism to do the above, including documentation. [SRM of 6/15/90, item 3]
H. Evaluate whether a 1 E-6 guideline for a large release would be practical and useful. [SRM of 6/15/90, item 2]
- 1. Use " partitioned" objectives to ensure defense-in-depth.1E-4 for CDF and 1E-1 for CCFP are acceptable. But, a " deterministic" objective in place of a CCFP value will also be acceptable. Dont impose these values as requirements, but use them for regulatory guidance. [SRM of W15/90, item 4]
J. " Strive for a risk level consistent with the safety goals in developing and revising regulations." (SRM of 6/15/90, item 6]
K. Evaluate IPE results as a whole and report to the Commission at completion of the IPE review process. [SRM of 5/10/90, item,1]
L "[Use] IPEs to enhance the understanding of the adequacy of our regulations through comparison with the Safety Goals." Especially to consider whether historic use of regulations has produced an ensemble of LWRs that meet the goal objectives. [SRM of 5/10/90, item 2]What is risk-based regulation and is it any good?
M. Commission should use the Safety Goal policy in a strat ic sense to support its tacit claim that existing plants operate within the Safety objectives. ~Ihe only tools available for doing this are the IPEs and other available PRAs and the Accident Soquence Precursor program. [ACRS letter of W12/92, ' implementation of the Safety GoalPolicy']
i N. Staff should develop a specrfic method for dealt with quantifiable uncertainty when companng calculated values of risk with Saf Goal objectives.- [ACRS letter of W12)92, ' implementation of the Safety Goal O. Given a pr ed change in regulat>ons or regulatory whether the change will reduce risk segrvpractice, the Staff should consider not ficantly, but also whether the ensemble plants to which the change would apply, fails to meet Safety goal j
objectives, i.e., is in need of a change. [ACRS letter of 6/12/92, "Implementaten of the safety GoalPolicy']
3 The three staff programs The Staff believes that three ongoing programs will satisfy these objectives and requirements. The programs are:
- 1) The Regulatory Review Group 1
intended to address "over regulation" described in a charter ap aroved by the Commission discussed at February 11 ACRS meeting intended to be a six-month effort 2] Bimination of requirements marginal to safety also intended to address "over regulation" l
input from industry, public, staff no overall strategy, each issue dealt with ad hoc except for indications that risk perspectrve will be used 3]IPE insights evaluation intended to address " regulatory gaps" to look at IPE results "as a whole consider implications about regulations Commission recommended evaluation against Safety Geal no description of this program is available Will the existing staff programs do what SRMs ask for and what ACRS has i
recommended?
The short answer is -- no.
The attached table lists the fifteen detailed objectives of a program that would seem to satisfy the Commission and ACRS and compares them wr'th what each of the three existing staff programs can be expected to accomplish.
The charter of the RRG includes a paragraph that could be construed to describe a program of the sort needed. However, no details are given. Most important, a strategy for canying out a program of the kind envisioned must be invented. No discussion of such a strategy is provided. Also the resources of RRG seem far too limited.
The " Program to Biminate Marginal Requirements" is good, but it does not do what is being asked for in the SRMs and by ACRS. Input to the program will consist of suggested examples of over regulation provided oy industry and others. Each issue will be considered by the staff on an ad hoc basis. There seems to be no overall strategy for how issues will be examined and evaluated, beyond a promise that PRA techniques will be used where applicable. It is not clear how the Safety Goal will be used, e.g., whether partitioned objectives will become decision thresholds, or how uncertainties in risk estimates will be dealt with. This is a bottom up program; PRA and perhaps the Safety Goal will be used to help evaluate issues identified industry and the public. It is not apparent that these suggestions derive from any systematic or coordinated effort. Apparently, the staff does not intend to suggest issues. There is no intent in the program to evaluate the entire body of regulations in a way the lets PRA and the SaTety Goal identify cases of inadequate or overreaching regulations or regulatory practice.
1 j
4 The third program, "to evaluate IPE insights," has not been described in any available documents.
Miscellaneous observations and comments on related subjects Should Safety Goal Objectives be thresholds or targetpoints? I believe they should be the latter but I doubt that there is general agreement, or that many have thought about the distinction. ACRS give it some consideration.
1 Let's assume that a regulation or ensemble of regulations causes the risk performance, in some parbcular area, of a particular class of plants to fall far below the Safety Goal objective - perhaps one of the partitioned objectives. Is that a good regulation? Should it be considered ripe for reevaluation? It may be that a vendor i
or a utility prefers to retain a certain plant feature that causes an aspect of risk to be far below a particular safety goal objective. But, what business does NRC have in insisting on that through its regulations?
A question might be raised about large uncertainty and that threshold or target point, it makes no dMference. But, that's a red herring with regard to this issue. The uncertainty question is a very important one, but it is a separate issue; perhaps related.
What is risk-based regulation and is it any good? What is performance-based regulation, and is it any good?
There is much loose talk, mainly at the speech-giving level about these concepts.
Some staff papers contrast " programmatic and com_pliance-based regulation" with
" performance-oriented and risk-based regulation". These are not necessarily contrasting a pproaches. Elsewhere the staff says they will use PRA and the Safety Goal in deve opment of non-prescriptive, performance-based regulations. Does anyone know what that means? ACRS ought to bring some precision to the discussion.
First, risk-based regulation in not the antrthesis of compliance-based regulation.
ACRS has been advocating for many years that risk concepts should be the (or at least a) basis for regulabons. That does not mean that the regulabons need be cast in risk terms, merely passed on to licensees. Rather, the same old style of [not as]
arbitrary rules and regulabons, easy to understand and easy to enforce, should remain. The NRC staff would take the responsibility for transforming the risk concepts into " deterministic" and prescriptive rules.
Second, performance-based rules might sometimes be a good idea, but not always. One of the most im x>rt aspects of plant performance that NRC would like to regulate is equipment anc system reliability. The problem is that reliability values considered to be desirable are well beyond what can easily be demonstrated through tests or plant experience. That is, through performance. Wrtness the EDG rule difficulty.
5 Capacity of a system can often more easily be subject to a performance regulation.
Appendix K for ECCS is essentially that. By a combination of tests and analysis [a performance) it can be shown that a particular ECCS will do what is expected of it, and it is not necessary to specify highly detailed requirements about pipe size and pump output.
But, if one wants to require that a pump or an EDG will start in 99.9% of trials, it takes a long time to demonstrate that performance. A simple performance-based requirement on starting reliability is thus impractical. It might be necessary or possible to use some surrogate measure of Intformance. Perhaps if the EDG will start within 10 seconds every time it is testecl (with some limited number of tests expected), then that means it will start 99.9% of the time under real conditions. But, who can prove that is a good surrogate?
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a COMPARISON OF OBJECTIVES OF A POSSIBLE NEW PROGRAM TO ASSESS REGULATIONS AGAINST SAFETY GOALS AND WHAT ONGOING STAFF PROGRAMS WILL PRODUCE
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Program to E!!minate Program 1o Evaluate Comment Detailed Objectives Regulatory Review Group Marginal Requirements IPE inalghts EFERENCES FOR RRG Charter nnd presentation at FRNs of 11/24/92 and 1/27/93 No program description is available
)NGOiNG PROGRAMS Feb.11 ACRS meeting SECY-92-263 SRM of 8/26/92 L Descrtbo a plan with The scope of a
- top down* plan is This is a
- bottom up* program. Changes specific detall mentioned, but no detail or clear identified by other misceifaneous will be strategy is described. RRG effort is evaluated, partialty with PRA and the SG.
too small to do this.
L Plan 13 eliminate This is mentioned in a general wey See A.
.r.: z 7 squirentente.
- 3. Plan for modifying This is mentioned in a general wmy Program is not intended 'o address this nedequate equiremente.
A Conalder a trial case The whole RRG effort might be Apparently, no plans for a trial program of of limited scope considered a trial scope program; it is limlted scope; although taking issues one not described as such.
at a time amounts to same thing.
L Elevde This is not discussed This is not discussed uprHguentitleblo leeues e the Commleelon
- 8. Routinely conalder RRG is ad hoc; no indication of plan Apparently this will be done for the issues ige when developing to set up a system for routine.
Identified during this program. No details egulatory changes ongoing assessments on how.
- 1. Formal mechanlem RRG is ad hoc; no indication of plan Nothing has yet been described.
or the routine reviewe to set up a system for formal assessment & documeritation
- t. Evoluele 1E-6 This was done in another program This was done in another program The large release guideline for large guideline has bee eloeos dropped
. Use partitioned No indication if or how RRG plans to No indication if or how this program will use ectives, e.g.
use quantitative objectives quantitative objectives a1E-4 CCFP = 1E-1
- 1. Risk level No indication RRG plans to deal with No indication this program wlit deal with the consistent" with SGe the ' threshold vs. target
- issue
" threshold vs, target" issue
[see text of report for discussion]
[see text of report for discussion]
COMPARISON OF OBJECTIVES OF A POSSIBLE NEW PROGRAM TO ASSESS REGULATIONS AGAINST SAFETY GOALS AND WHAT ONGOING STAFF PROGRAMS WILL PRODUCE Program to Eliminate Program to Evaluate 3etelled Objectives Regulatory Review Group Merginal Requiremente iPE Insights Comment
.. Evoluete IPE roeutte Not applicable Not applicable This will have to be the focus of an o o whole eventual program
. Compere IPE resulte Not applicable Not applicable We will have to wait and see how a SG to essees -
lotoric effect of and how well this will be done O_ ' :^" - -
- 1. Commiselon use of Not in the program Not in the program V./PRA & ASP to onfirm confklence in
. W regulatione
- 1. Staff should develop Not in the program Not in the program isene to use uentitled uncertainty
- e. Staff should conalder Not in the program Not in the program lente statue vs. SG to seeeschange
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