March 19, 1998
| MEMORANDUM TO: |
L. Joseph Callan
Executive Director for Operations |
| FROM: |
John C. Hoyle, Secretary /s/ |
| SUBJECT: |
STAFF REQUIREMENTS - SECY-97-287 - FINAL REGULATORY GUIDANCE ON RISK-INFORMED REGULATION:POLICY ISSUES |
The Commission has approved the staff's recommendation to allow very small increases in core damage frequency (CDF)
and large early release frequency (LERF) independent of the baseline calculated CDF/LERF, provided that licensees track
and the NRC staff monitor the cumulative effect of changes. The Commission also approved the definition of "very small"
as changes less than 10-6 per reactor year for CDF and less than 10-7 per reactor year for LERF. The staff should recognize
that risk insights continue to be one input to the integrated decision making process and the proposed values should be
considered a guideline and not a hard cut-off.
The Commission has approved the staff's recommendation for the treatment of uncertainties in PRA results. As the pilot
programs are completed, the salient features of the decision making process should be documented to the Commission to
ensure a consistent, scrutable and common understanding as to how risk-informed decisions should be promulgated. In
particular, the paper should clarify the treatment of uncertainties and the role of increased NRC management attention in
the decision making process in the pilot programs.
The staff should assess for future Commission consideration industry programs for standardizing and certifying nuclear
facility PRAs.
|
(EDO) |
(SECY Suspense: 10/30/98) |
As part of the FY 1999 budget, the Commission approved "... development of improved human and organizational
reliability analysis and data, and to perform additional risk studies associated with reactor low power and shutdown
operation." However, the Commission has not approved the staff's recommendation that consideration of possible
additional shutdown risk acceptance guidelines be undertaken as part of the research effort. The staff should inform the
Commission of the results of these risk studies for future Commission consideration. The Commission has approved the
recommendation to maintain the CDF and LERF guidelines for both power and shutdown operations. The staff should
appropriately credit compensatory measures taken to mitigate increases in CDF and LERF during shutdown or outage
conditions.
The Commission has approved the staff's recommendation to conduct an assessment of risk- informed acceptance
guidelines for temporary changes to plant configurations. The Commission noted that this effort will take place in the
future. At present, except for the special case of Technical Specification changes, only time-averaged guidelines will be
used. In assessing these acceptance guidelines for temporary plant configurations, staff should weigh the merits of
temporary changes that may lead to improved safety, and should ensure that appropriate compensatory measures are taken
into account that could mitigate the conditional CDF and LERF. This issue will also arise in the context of the proposed
change to the Maintenance Rule under which configuration control during maintenance would become a requirement, but
not all temporary changes will come under the Maintenance Rule even after the proposed revision is finalized. The staff
should ensure a consistent approach is used for future revisions to Regulatory Guide 1.174 and Regulatory Guide
1.160/NUMARC 93-01.
In addition, a risk-informed approach should not focus exclusively on when risk increases should be allowed. If risk
insights reveal significant vulnerabilities, risk reduction may be the appropriate goal for both licensees and the
Commission.
| cc: |
Chairman Jackson
Commissioner Dicus
Commissioner Diaz
Commissioner McGaffigan
OGC
CIO
CFO
OCA
OIG
Office Directors, Regions, ACRS, ACNW, ASLBP (via E-Mail)
PDR
DCS |
