ML16216A092

The Nuclear Energy Institute Petition for Rulemaking to Amend 10 CFR 50.48, Fire Protection

ML16216A092
Person / Time
Issue date:	09/15/1995
From:	Kress T Advisory Committee on Reactor Safeguards
To:	Taylor J NRC/EDO
References
Download: ML16216A092 (3)

Text

September 15, 1995 Mr. James M. Taylor Executive Director for Operations U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001

SUBJECT:

THE NUCLEAR ENERGY INSTITUTE PETITION FOR RULEMAKING TO AMEND 10 CFR 50.48, "FIRE PROTECTION" During the 424th meeting of the Advisory Committee on Reactor Safeguards, September 7-8, 1995, we completed our discussion regarding the subject rulemaking petition. Our Auxiliary and Secondary Systems Subcommittee met on June 7, 1995, to begin the review of this matter. During these meetings, we had the benefit of discussions with representatives of the staff, the Nuclear Energy Institute (NEI), and the Electric Power Research Institute (EPRI). We also had the benefit of the documents referenced.

The NEI petition for rulemaking proposes to amend 10 CFR 50.48, "Fire Protection," by adding an Appendix S, which is described as a "performance-based" alternative to the existing prescriptive Appendix R. NEI believes that the recommended addition to 10 CFR 50.48 will be "safety neutral" and that considerable cost savings will result.

We support risk-based regulations. It is not clear, however, how performance-based regulations should be developed from risk consideration. It is our perception that such regulations should include the following elements:

Clearly stated objectives with demonstrable performance requirements, expressed either in deterministic or probabilistic terms.

Flexibility in the methods that the licensee is permitted to use to meet the performance goals or criteria. These methods should be supported by operational experience and experimental results.

The regulatory body must have a valid means to establish that the performance criteria have been met.

Unfortunately, the proposed rule in the NEI petition is deficient in all these elements.

The objective of the proposed rule is to assure "that the safety functions required to safely shut a plant down and maintain it in a safe condition are maintained during and following a fire." It is further stated that fire modeling, as well as PRAs, may be used to identify the pertinent performance criteria. The proposed rule, however, avoids setting probabilistic requirements and uses non-quantitative language. Thus, there are references to "credible" fires and "credible" scenarios, as well as to "adequate" time for completing safety functions. These concepts need to be defined in quantitative, probabilistic terms. For example, we would expect a quantitative performance requirement for the probability that fire will compromise safe shutdown equipment and lead to core damage.

Some of the issues that the proposed rule raises could be naturally resolved in a PRA context. Examples are the inadvertent actuation of automatic suppression systems and the relevance of the current requirements regarding the concurrent occurrence of a fire and loss of offsite power. In addition, the proposed rule does not address the issue of transient fuels. PRAs have shown that, in some cases, transient fuels are required to produce fires of severity sufficient to damage redundant safety systems. Such transient fuels have been found in controlled areas in the past. Not only are transient fuels not addressed, the proposed rule suggests that some administrative controls dictated by Appendix R may be eliminated. We would prefer to see an evaluation of such issues in the context of a fire PRA.

We are concerned that neither the NRC nor NEI has any plans for conducting fire tests for refining the probabilistic analysis of time-to-suppression. We also have concerns about weakening the requirement for automatic fire detection systems, the lack of a methodology for treating the potentially damaging effects of smoke, the use of a limited fire initiation database, and the neglect of consideration of fire during shutdown. We will address these concerns should the rulemaking process advance.

Even though we support the use of PRA in the development of a performance-based rule, we note that, given the uncertainties in the state of the art, fire PRAs cannot be the sole basis for regulatory requirements. Developing the right mix of criteria based on PRA and criteria based on good engineering practice is a challenge and a necessary requirement for a well-written rule.

We believe it will take some time and resources to develop and institute performance-based fire regulation. We also believe doing so is an important step in the agency's move in this direction.

Additional comments by ACRS Members George Apostolakis, James C.

Carroll, and Ivan Catton are presented below.

Sincerely,

/s/

T. S. Kress

Chairman Additional Comments by ACRS Members George Apostolakis, James C.

Carroll, and Ivan Catton We support the Committee letter but have further comments for your consideration. The use of performance-based rules for fire protection is frustrated by conventional attitudes. The desire of regulators to have simple rules and tests for administrative convenience contrasts with the need of plant operators to have flexibility to arrive at optimal solutions. Unfortunately, the prescriptive characteristics embodied in regulations are accepted without proof, while any engineering solution supporting a performance requirement is subjected to a disproportionately higher standard of proof.

References:

1. Letter dated February 2, 1995, from W. Rasin, Nuclear Energy Institute, to John C. Hoyle, Acting Secretary, NRC,

Subject:

Petition for Rulemaking to Amend 10 CFR 50.48

2. SECY-94-090 dated March 31, 1994, from James M. Taylor, Executive Director for Operations, NRC, to the Commissioners,

Subject:

Institutionalization of Continuing Program for Regulatory Improvement

3. SECY-95-034 dated February 13, 1995, from James M. Taylor, Executive Director for Operations, NRC, to the Commissioners,

Subject:

Status of Recommendations Resulting from the Reassessment of the NRC Fire Protection Program

4. Memorandum dated December 30, 1994, from James M. Taylor, Executive Director for Operations, NRC, to the Commissioners,

Subject:

Eighth Quarterly Report on the Status of the Thermo-Lag Action Plan