ML20046C983
| ML20046C983 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 08/09/1993 |
| From: | Donnelly P CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| RTR-NUREG-0828, RTR-NUREG-828, TASK-03-02, TASK-03-04.A, TASK-03-04.B, TASK-03-05.A, TASK-03-05.B, TASK-03-06, TASK-03-10.A, TASK-05-05, TASK-05-10.A, TASK-05-11.A, TASK-05-11.B, TASK-06-04, TASK-09-05, TASK-3-10.A, TASK-3-2, TASK-3-4.A, TASK-3-4.B, TASK-3-5.A, TASK-3-5.B, TASK-3-6, TASK-5-10.A, TASK-5-11.A, TASK-5-11.B, TASK-5-5, TASK-6-4, TASK-9-5, TASK-RR GL-81-10, GL-88-20, NUDOCS 9308130167 | |
| Download: ML20046C983 (7) | |
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Consumers Patrick M Donneny Plant Manager AUCN#5AN5 PROGRESS Beg Rock Point Nuclear Plant,102E9 US 31 North, Charlevom. MI 49720 August 9, 1993 Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 DOCKET 50-155 - LICENSE DDR BIG ROCK POINT PLANT -
UPDATE RESPONSE TO GENERIC LETTER 88 INDIVIDUAL PLANT EXAMINATION FOR SEVERE ACCIDENT VULNERABILITIES Since the response to Generic letter 88-20, Individual Plant Examination for Severe Accident Vulnerabilities dated October 25, 1989, the submitted schedule has been revised twice.
Integrated Plan Semi-Annual Updates No 12 and No 13 reflected proposed submittal dates of 8/1/92 and 9/1/93 respectively.
The purpose of this letter is to inform the Staff that the current schedule plan is being revised for submittal by May 1,1994.
A brief history of the Probabilistic Risk Assessment (PRA), PRA applications and accident management at Big Rock Point is reiterated followed by a discussion of recent BRP activities that have affected the IPE schedule.
HISTORY Big Rock Point first became involved in PRA as a result of the accident at Three Mile Island (TMI). The proposed generic modifications-resulting from that accident were in excess of 200 million dollars.
Since Big Rock Point is a significantly different reactor design than other BWR's, Consumers Power Company was not assured that the proposed modifications would indeed improve safety at Big Rock Point. As a result of these concerns, Consumers Power Company asked for and received a deferral from' implementing the THI action -
plan until a comprehensive risk analysis could be completed.
On March 31, 1981 Consumers Power Company submitted a level 3 PRA to the Commission. The submittal requested seven exemptions from requirements of the TMI action plan and proposed seven alternative modifications to Big Rock Point that would improve risk. Consumers Power Company also committed to establish a Continued Risk Management Plan (CRMP) which would use the PRA as a tcol to evaluate both future generic issues and operating experience to assist in f
determining the need for modifications to plant systems or procedures. Big gi Rock's continuing risk management is in many ways equivalent to severe j
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NUCLEAR REGULATORY COMMISSION 2
BIG ROCK POINT PLANT UPDATE RESPONSE TO GENERIC LETTER 88-20 August 9, 1993 By letter dated May 17,1984 (Crutchfield to VandeWalle) the NRC staff completed its review of the Big Rock Point PRA with the assistance of two contractors, EG&G and Brookhaven National Laboratory (BNL). The subsequent Safety Evaluation Report (SER) concluded that Consumers Power Company has performed a credible job in completing the Big Rock Point PRA.
The SER went on to state that the fault trees and event trees were adequately developed and properly. identified the dominant accident sequences.
Appropriate. failure data were used and plant systems were accurately represented. The containment failure mode and consequences analysis properly identified the dominant containment failure modes, and estimated consequences in terms of dose and fatalities.
Since the completion of the original Big Rock Point PRA and to compliment the CRMP program, Consumers Power Company has created and maintained a risk assessment group located at the plant site. The mission of this group has been to support the plant in various areas and to address and utilize the 1981 risk assessment results.
Examples of present CRMP and other plant responsibilities include:
Plant Technical Review Group (TRG) support which provides the ranking of issues for the integrated living schedule; Training Department support to dominant accident sequence training and Emergency Operating Procedures; Generic letter, Bulletin and rule support; Region audit inspection support; training simulator support; selected 10 CFR 50.59 review; preventative maintenance program' support; plant accident _and transient analysis; and emergency drill coordination, assistance, and management.
In addition to the above mentioned support activities several applications of the Big Rock Point PRA have been performed. Attachment 1.provides a summary of'a number of these applications. Several plant modifications and procedure changes have resulted from the 1981 study as well as from the subsequent-applications.
Plant modifications addressing key outliers include - early enclosure spray, PIS valve position locks, redundant primary system isolation valves, the alternate shutdown panel siesign (a combination Level 3 and
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Appendix R identified plant change), secondary system instabilities, i.e.,
preselected recirc pump trip on loss of load etc.
Examples of procedure changes include fire water addition to the hotwell, containment flooding guidelines, shutdown cooling system isolation etc.
Examples of already in place severe accident management strategies range from the above procedural
' NUCLEAR REGULATORY COMMISSION 3
BIG ROCK POINT PLANT UPDATE RESPONSE TO GENERIC LETTER 88-20 August 9, 1993
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changes to the control room design review effort and the shift staffing analysis. These changes when analyzed in aggregate are expected to result in an order of magnitude reduction in the baseline core damage frequency.
EECENT BRP ACTIVITIES Recent plant activities such as the construction of the plant specific simulator, resolution of the Station Blackout Rule, Alternate Rod Injection t
exemption, support of the M0V program, Fire Pump and EDSFI inspection activities have affected the IPE schedule.
The dedication of PRA resources to support the simulator development was a decision that was conducted according to the Big Rock Integrated Plan guidelines. The basis of the decision was two-fold; first, NRC rules take precedence over Generic Letters, Bulletins etc; and second,' the key outliers, applications, and procedure changes identified by the 1981 study and subsequent industry issues had been previously addressed.
Furthermore,.the most uncertain aspect of any risk study are the human error assumptions and the common cause models.
Hence, Big Rock, by addressing the simulator rule has implicitly reduced the large uncertainties effecting human error probability modeling by improving operator understanding of severe accident processes. Moreover, a conscious decision was made during the construction to include a detailed secondary plant model (this was not a requirement of the BRP Limited Scope Simulator Application) to allow a more extensive schooling on secondary plant evolutions (a.k.a., secondary system instabilities as identified in 1981) such as loss of load, loss of the main condenser, loss of feedwater, loss of instrument air and turbine trip whose annual event frequencies range from 0.06 to 1.4.
[URRENT IPE STATUS Currently Consumers Power Company is updating the 1981 Big Rock Point risk
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assessment. The latest industry developments are being factored into the study. The best features of a variety of vendor-codes are being utilized to perform the Big Rock study.
For example; INEL IRRAS 4.16 is being used as the l
integrated analytical level.1 tool; PL&G Riskman Release 4.0 is being used to i
perform the basic event statistical analyses; SAIC's' CAFTA is being used for 1
presentation graphics; Logic Analyst's Incorporated SETS code is being used for independent event classification; and the Advanced Reactor Severe Accident Program Generalized Containment Model is being used to. ascertain everything j
from local hydrogen pocketing potential to equipment environmental qualification requirements.
The utilization and integration of these codes not only facilitates and demonstrates Big Rock's intent on completing the study but also prepares the plant staff for supporting the maintenance rule, forthcoming Generic Letters etc, as well as integrated risk based regulation issues such as day-to-day operational configuration management.
. Present results to date have not identified any new outliers. The latest core damage frequency and release fraction calculations are less than reported in 1981.
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NUCLEAR REGULATORY COMMISSION 4
BIG ROCK POINT PLANT URDATE RESPONSE TO GENERIC LETTER 88-20 August 9, 1993
SUMMARY
In summary, Consumers Power Company believes that, the key outliers identified in the 1981 study have been addressed; that severe accident management strategies have already been incorporated into the E0Ps; and that some of the critical 1981 identified uncertainties have been reduced by modifications such as construction of a plant specific simulator. The present IPE effort is viewed as a risk tuning exercise that will support end of license assessments, maintenance activities, and plant operational risk monitoring.
In order to provide a quality and comprehensive updated risk profile Consumers Power requires an extension of the submittal to May 1, 1994.
f*;l Patri&k M Donnelly Patrick H Donnelly Plant Manager
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CC: Administrator, Region III, USNRC NRC Resident Inspector - Big Rock Point ATTACHMENT h
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ATTACHMENT CONSUMERS POWER COMPANY BIG ROCK POINT PLANT DOCKET 50-155 ATTACHMENT TO UPDATED RESPONSE TO GENERIC LETTER 88-20 2 PAGES
ATTACHMENT TO UPDATED RESPONSE TO GENERIC LETTER 88-20 l
(IPE FOR SEVERE ACCIDENT VULNERABILITIES)
SOURCE TITLE / ISSUE REFERENCE 1
SEP Topic:
III-2 and Wind and Tornado Loadings SER dated 9/22/87 III-4.A Tornado Missiles III-4.B Turbine Missiles (subsequent to final SER dated 11/29/82 SER additional comments are included in the final NUREG-0828 report dated 5/84)
III-5.A Effects of Pipe Break On Structures, SER dated 9/22/83 Systems, and Components Inside Contain-ment (High Energy Line Break)
III-5.B Pipe Break Outside of Containment NUREG-0828 report 5/84 (Screenhouse Flooding)
III-6 Seismic Design Considerations (Seismic NUREG-0828 report 5/84
" Weak-Link" approach to identify selective plant seismic improvements)
III-10.A Thermal-Overload Protection for Motor-NUREG-0828 report 5/84-Operated Valves V-5 Reactor Coolant Pressure Boundary NUREG-0828 report 5/84 (RCPB) Leak Detection (Unidentified Leakage Detection)
V-10.A Residual Heat Removal Heat Exchanger NUREG-0828 report 5/84 Tube Failures V-11.A Requirements for Isolation of High and SER dated 12/15/82 Low Pressure Systems V-11.B Residual Heat Removal Interlock System SER dated 12/15/82 Requirements (Interfacing System Loss of Coolant Accident)
VI-4 Containment Isolation System (sub NUREG-0828 report 5/84 topics listed below).
Need for a back-up Main Steam NUREG-0828 report 5/84 Isolation Valve Instrument and Service Air Line NUREG-0828 report 5/84 Auto Isolation Heating, Cooling, and Service Water NUREG-0828 report 5/84' Auto Isolation Treated Waste Auto Isolation NUREG-0828 report 5/84 Containment air lock testing Exemption dated 1/8/86 (received Appendix J exemption)
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ATTACHMENT TO UPDATED RESPONSE TO GENERIC LETTER 88-20 (IPE FOR SEVERE ACCIDENT VULNERABILITIES)
SOURCE TITLE / ISSUE REFERENCE SEP Topic:
IX-5 Ventilation Systems NUREG-0828 report 5/84 OTHERS:
Generic Letter Shift Staffing Requirements SER dated 12/30/83 81-10 10 CFR 50.62 Automatic Recirculation Pump Trip SER dated 3/20/86 10 CFR 50.62 Anticipated Transients Without SCRAM SER dated 6/17/92 (Alternate Rod Injection)
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