NEI Draft White Paper. Use of the Generic Letter Process and Alternative Source Terms in the Context of Control Room Habitability

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1 I. Current Situation A number of plants either have conducted, or plan to conduct in the near term, tracer gas testing of the control room envelope to determine if design and licensing basis inleakage assumptions are satisfied. If measured in-leakage is greater than the amount assumed in the licensing basis radiological consequences analysis, the licensee must perform an operability determination to verify that the control room ventilation system can accomplish necessary safety functions. This is considered a generic issue. Given the low probability of a design basis accident and the conservatism inherent in dose calculations, including the conservatism in the source term itself, the issue is not considered an immediate safety concern. II. Problem Statement A generic licensing issue has been raised by NRC reviewers and inspectors about the acceptability of licensees using an alternative source term (without prior NRC staff review and approval) in a Generic Letter evaluation to justify continued operation with a control room ventilation envelope that has been shown by tracer gas test to be in a degraded or nonconforming condition. III. The Generic Letter Process Generic Letter 91-18, Revision 1, directs licensees to make an operability determination and take follow-up corrective action whenever a structure, system, or component (SSC) is found to be degraded or nonconforming. A degraded condition is a condition of an SSC in which there has been a loss of quality or functional capability. A nonconforming condition is a condition of an SSC in which there is failure to meet requirements or licensee commitments. The scope of applicable SSCs is given in the Generic Letter. The primary reference defining operability is the plant-specific Technical Specifications. The primary reference for defining functionality is the set of plantspecific design and licensing basis documents, primarily the Updated Final Safety Analysis Report. The primary reference for defining the restoration of full qualification is 10 CFR 50, Appendix B, Criterion XVI, Corrective Action. The operability determination must be prompt, with timeliness commensurate with the safety significance of the issue. The determination can be based on analysis, testing, experience, compensatory measures, engineering judgment, or a combination of these factors, taking into consideration system functional requirements described in design and licensing basis documents. The scope of the determination must be sufficient to address the capability of relevant SSCs to perform their safety functions given the degraded or nonconforming condition. Additional information on safety functionality is given in NEI 97-04, Revision 1. 1

2 If the operability determination has a positive outcome, the plant may continue to operate on an interim basis with a degraded or nonconforming condition. Timely corrective action must then be taken to reconcile the degraded or nonconforming condition (i.e., restore full qualification in accordance with the plant s licensing basis, or revise the licensing basis in accordance with the appropriate regulatory change process). IV. The Alternative Source Term Regulation (10 CFR 50.67) A final rule on the use of alternative source terms at operating reactors was promulgated in The final rule recognized that significant advances have been made in understanding fission product releases from severe accidents. The revised source terms discussed in the final rule offer a more representative description of radionuclide composition and release timing. 10 CFR 50.67(b)(1) specifies that a licensee who seeks to revise its current accident source term in the design basis radiological consequence analyses shall apply for a license amendment under In other words, a licensee cannot use 10 CFR to change its licensing basis to incorporate alternative source term methodology without prior NRC staff review and approval. However, the final rule does not discuss the use of alternative source terms in the context of the Generic Letter process, which is not a process for changing the licensing basis, but is a process for justifying continued operation until corrective action can be taken to reconcile a degraded or nonconforming condition. One option chosen by a licensee to reconcile a degraded or nonconforming condition may in fact be a formal license amendment request under 10 CFR to revise the licensing basis, in this case to formally incorporate an alternative source term. Another option would be to perform an engineering evaluation to establish interim operability pending corrective action (an engineering evaluation in the context of Generic Letter is not considered a change to the licensing basis and is not considered a compensatory action). V. Use of Alternative Source Terms in a Generic Letter Evaluation of Control Room Habitability Regulatory Guide 1.196, Control Room Habitability at Light Water Nuclear Power Reactors, Regulatory Position 2.7.3, addresses methods available to address short term degraded or nonconforming conditions. RG refers to additional guidance in NEI 99-03, RG 1.183, RG 1.194, and RG However, this guidance is limited to the use of self-contained breathing apparatus (SCBA) or potassium iodide (KI) as compensatory measures. The purpose of this White Paper is to establish engineering judgment, with 2

3 reliance on alternative source terms, as another valid option to address short term degraded or nonconforming conditions. The option of performing an engineering evaluation using an alternative source term would be an effective initial approach to realistically evaluate control room radiological consequences. It is important to note that use of an alternative source term in an engineering evaluation conducted as part of the Generic Letter process is not a compensatory action subject to further evaluation under 10 CFR if it does not involve a plant modification, a procedure change, or a change to the design or licensing basis. Additional detail on the relationship between compensatory actions and 10 CFR can be found in NEI 96-07, Revision 1. Long-term corrective action would involve full restoration of the design and licensing basis described in relevant documentation. This may involve, for example: 1. a facility or procedure modification to reduce the in-leakage to a value within that assumed in the safety analysis, 2. a license amendment request for NRC staff approval of a change to the licensing basis to recognize the benefits of the alternative source term and to increase the allowable in-leakage, 3. a license amendment request for NRC staff approval of a change to the licensing basis to accept the as-found in-leakage condition, or 4. a combination of the above. VI. Industry Proposal If a tracer gas test indicates a degraded or nonconforming condition (design or licensing basis control room in-leakage assumptions are not satisfied), the least burdensome corrective action to establish interim operability would be to perform an engineering evaluation based on an alternative source term. The licensee could then determine the most efficient and effective way to exit the corrective action process, which likely would be to incorporate the alternative source term into the plant s design and licensing basis (example 3 above). VII. Proposed Followup Action NRC and industry perform a peer review of this White Paper to facilitate joint acceptance of the near-term use of alternative source terms by licensees in a Generic Letter context to justify continued plant operation following deficient tracer gas test results, assuming such operation does not conflict with any laws, regulations, license conditions, or Technical Specifications. NRC/NEI conduct public meetings to assist implementation of generic resolution. 3

4 VIII. References 1. NRC, 10 CFR 50, Appendix A, General Design Criterion 19, Corrective Action. 2. NRC, Generic Letter 91-18, Rev. 1, October 8, NRC, Final Rule, 64 FR 71990, Use of Alternative Source Terms at Operating Reactors, December 23, NRC, NUREG -0800, Standard Review Plan, Chapter , Radiological Consequence Analyses Using Alternative Source Terms, Rev. 0, July NRC, NUREG-1430 through NUREG-1434, Standard Technical Specifications, Rev NRC, Regulatory Guide 1.183, Alternative Radiological Source Terms for Evaluating Design Basis Accidents at Nuclear Power Reactors, July NRC, Regulatory Guide 1.187, Guidance for Implementation of 10 CFR 50.59, Changes, Tests, and Experiments, November NRC Regulatory Guide 1.194, Atmospheric Relative Concentrations for Control Room Radiological Habitability Assessment at Nuclear Power Plants, June NRC, Regulatory Guide 1.196, Control Room Habitability at Light Water Nuclear Power Reactors, May NRC, Regulatory Guide 1.197, Demonstrating Control Room Envelope Integrity at Nuclear Power Reactors, May NRC, Generic Letter , Control Room Habitability, June 12, NRC, Transcript of Operability Workshop held on August 14, 2003 (ADAMS Accession Number ML ). 13. NEI, Guideline 96-07, Revision 1, Guidelines for 10 CFR Implementation, November NEI, Guideline 97-04, Revision 1, Design Basis Program Guidelines, February NEI, Guideline 98-03, Revision 1, Guidelines for Updating Final Safety Analysis Reports, June NEI, Guideline 99-03, Revision 1, Control Room Habitability Guidance, March

5 17. NEI, Guideline 99-04, Guidelines for Managing NRC Commitment Changes, July Technical Specification Task Force, TSTF Traveler 448, Revision 1, Control Room Habitability, August 18,