ML030700177

Guidance for Licensee Review of Preliminary ASP Analysis (Enclosure 2)

ML030700177
Person / Time
Site:	Point Beach
Issue date:	03/13/2003
From:	Spaulding D NRC/NRR/DLPM/LPD3
To:	Cayia F Nuclear Management Co
Spaulding D
References
Download: ML030700177 (3)

Text

Enclosure 2 GUIDANCE FOR LICENSEE REVIEW OF PRELIMINARY ASP ANALYSIS Background and

- loss of offsite power (LOSP).

The preliminary precursor analysis of an event or condition that occurred at your plant has The only support system modeled in Rev. 2 is been provided for your review. This analysis the electric power system.

was performed as a part of the NRCs Accident Sequence Precursor (ASP) Program. The ASP

• SPAR Rev. 3 models are currently being Program uses probabilistic risk assessment developed to replace Rev. 2 models. The techniques to provide estimates of operating newer revision models have 11 types of event significance in terms of the potential for initiating events:

core damage.

- transients, The types of events evaluated include actual - small LOCAs, initiating events, such as a loss of off-site power - medium LOCA, or loss-of-coolant accident, degradation of plant - large LOCA, conditions, and safety equipment failures or - interfacing system LOCA, unavailabilities that could increase the - steam generator tube rupture (PWR only),

probability of core damage from postulated - LOSP, accident sequences. - loss of component cooling water (PWRs only),

This preliminary analysis was conducted using - loss of service water, and the information contained in the plant-specific - loss of DC power.

final safety analysis report (FSAR), individual plant examination (IPE), and other pertinent Both revisions have transfer events trees for reports, such as the licensee event report (LER) station blackout and anticipated transient and/or NRC inspection reports. without scram.

Modeling Techniques The models may be modified to include additional detail for the systems/components of The models used for the analysis of events interest for a particular event. This may include were developed by the Idaho National additional equipment or mitigation strategies as Engineering and Environmental Laboratory. outlined in the FSAR or IPE. Probabilities are The models were developed using the Systems modified to reflect the particular circumstances Analysis Programs for Hands-on Integrated of the event being analyzed.

Reliability Evaluations (SAPHIRE) software.

The developed models are called Standardized Guidance for Peer Review Plant Analysis Risk (SPAR) models. The SPAR models are based on linked fault trees. Fault Comments regarding the analysis should trees were developed for each top event on the address:

event trees to a super component level of detail.

• Does the "Event Summary" section:

Two revisions of the SPAR models are currently being used in the ASP analysis: SPAR Rev. 2 - accurately describe the event as it occurred; and SPAR Rev. 3. and

• SPAR Rev. 2 models have four types of - provide accurate additional information initiating events: concerning the configuration of the plant and the operation of and procedures

- transients, associated with relevant systems?

- small loss-of-coolant accidents (LOCAs),

- steam generator tube rupture (PWR only),

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• Does the "Modeling Assumptions" section: This documentation must be current at the time of the event occurrence. Systems, equipment,

- accurately describe the modeling done for or specific recovery actions that were not in the event; place at the time of the event will not be considered. Also, the documentation should

- accurately describe the modeling of the address the impact (both positive and negative) event appropriate for the events that of the use of the specific recovery measure on:

occurred or that had the potential to occur under the event conditions; and

• the sequence of events,

- include assumptions regarding the

• the timing of events, likelihood of equipment recovery?

• the probability of operator error in using the Appendix G of Reference 1 provides examples system or equipment, and of comments and responses for previous ASP analyses.

• other systems/processes already modeled in the analysis (including operator actions).

Criteria for Evaluating Comments An Example of a Recovery Measure Modifications to the event analysis may be Evaluation made based on the comments that you provide.

Specific documentation will be required to A pressurized-water reactor plant experiences a consider modifications to the event analysis. reactor trip. During the subsequent recovery, it References should be made to portions of the is discovered that one train of the auxiliary LER or other event documentation concerning feedwater (AFW) system is unavailable. Absent the sequence of events. System and any further information regrading this event, the component capabilities should be supported by ASP Program would analyze it as a reactor trip references to the FSAR, IPE, plant procedures, with one train of AFW unavailable. The AFW or analyses. Comments related to operator modeling would be patterned after information response times and capabilities should gathered either from the plant FSAR or the IPE.

reference plant procedures, the FSAR, the IPE, However, if information is received about the or applicable operator response models. use of an additional system (such as a standby Assumptions used in determining failure steam generator feedwater system) in probabilities should be clearly stated. recovering from this event, the transient would be modeled as a reactor trip with one train of Criteria for Evaluating Additional Recovery AFW unavailable, but this unavailability would Measures be mitigated by the use of the standby feedwater system.

Additional systems, equipment, or specific recovery actions may be considered for The mitigation effect for the standby feedwater incorporation into the analysis. However, to system would be credited in the analysis assess the viability and effectiveness of the provided that the following material was equipment and methods, the appropriate available:

documentation must be included in your response. This includes: - standby feedwater system characteristics are documented in the FSAR or accounted for in

• normal or emergency operating procedures, the IPE,

• piping and instrumentation diagrams (P&IDs), - procedures for using the system during recovery existed at the time of the event,

• electrical one-line diagrams,

- the plant operators had been trained in the

• results of thermal-hydraulic analyses, and use of the system prior to the event,

• operator training (both procedures and - a clear diagram of the system is available simulation). (either in the FSAR, IPE, or supplied by the 2

licensee), Schedule

- previous analyses have indicated that there Please refer to the transmittal letter for would be sufficient time available to schedules and procedures for submitting your implement the procedure successfully under comments.

the circumstances of the event under analysis, and Reference

- the effects of using the standby feedwater 1. R. J. Belles, et al., Precursors to Potential system on the operation and recovery of Severe Core Damage Accidents: 1997, A systems or procedures that are already Status Report, USNRC Report included in the event modeling. In this case, NUREG/CR-4674 (ORNL/NOAC-232) use of the standby feedwater system may Volume 26, Lockheed Martin Energy reduce the likelihood of recovering failed Research Corp., Oak Ridge National AFW equipment or initiating feed-and-bleed Laboratory, and Science Applications due to time and personnel constraints. International Corp., Oak Ridge, Tennessee, November 1998.

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