ML20049A700
| ML20049A700 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 09/21/1981 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20049A697 | List: |
| References | |
| NUDOCS 8110010428 | |
| Download: ML20049A700 (5) | |
Text
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NUCLEAR REGULATORY COMMISSION g
,g WASHINGTON, D. C. 20555
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO. 48 TO FACILITY OPERATING LICENSE NO. DPR-6 CONSUMERS POWER COMPANY BIG ROCK POINT PLANT DOCKET NO. 50-155 r
1.0 INTRODUCTION
'By letter dated February 25, 1980 and supr..ements dated June 19, 1981, July 22,1981, and September 3,1981, Consumers Power Company (the licensee) requested an amendment to Facility Operating License No. DPR-6 for the Big Rock Poing Plant. This amendment would add reactor operating-limits for operation with one recirculation loop out of service.
In a related action, the Commission issued Amendment No. 44 on June 9,1981 which authorized a change in the reactor operating limits for operation wfth both recirculation loops in service.
2.0 BACKGROUND
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.r.a.
The licensee's February 25. 1980 submittal recoested (1) revised reactor
~ cing lim a for c:eration with
- th recir;ul a
- ir 'ec;s ; ' service, and (2) operating limits for one recirculation loop out cf service for the Big Rock Point Plant.
Amendment No. 44 dated June 9,1981 approved new ECCS operating limits for two loop operation.
By letters dated June 19, 1981 and July 22, 1931, Consuners Power Company provideJ additional information with regard to single loop operation. This safety evaluation addresses operation with one recirculation loop in service.
3.0 DISCUSSION AND EVALUATION The NRC staff has completed a review of the March 31, 1977, General Electric (GE) Big Rock Point ECCS analysis (reference 1) for single loop operation.
Although single loop operation (SLO) is still an outstanding issue in jet pump BWRs, Big Rock Point is a non-jet pump BWR and has sufficiently demon-strated that this mode of operation is safe and acceptable.
8110010428 810921:
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2-The GE analysis is performed with the same codes as used in the two loop case.
Certain input parameters are modified to simulate single loop operation.
In the analysis, the location of the worst break wa's determined to be in the 20-inch recirculation discharge of the isolated loop.
Further analyses of a break spectrum was made for the worst break location. A 0.5 ft2 break was determin'ed to result in the highest calcult.ted peak cladding temperature of 2192 F with a local oxidation of 7.2%.
A detailed description of the codes used can be found in _NEDE-20566, " General Electric Company Analytical Model for Loss-of-Coolant Analysis in Accordance with 10 CFR 50 Appendix K."
Although this would appear to satisfy requirements, Big Rock Point is in a ' unique situation with respect to the simultaneous or exclusive use of EXXON or GE fue' during a particular cycle. The use of a GE two loop LOCA analysis to describe the behavior of an all EXXON core in a transient situation was a previous staff concern and was reviewed and found acceptable in reference 2.
A further complication arises by the fact that there was no SLO ECCS performed for EXXON fuel.
Rather than performing EXXON SLO ECCS, the licensee proposed to place a 20% MAPLHGR reduction (reference 3) on the EXXON fuel whereas GE fuel has only a 5% MAPLHGR reduction.
The 5% MAPLHGR reduction' Yor GE fuel is a result of faster core uncovery in SLO. The staff has concluded that the 20% raduction for EXX0N fuel is an adequate margin such that in the event of a LOCA, the fuel would not be expected to violate 10 CFR 50.46 limits.
In reference 4, the licensee stated that an Exxon analysis would probably predict a similar responfe~ti the most limiting break situation during single loop operation. This can be based on the ei-ilarity between EUON and GE twc 1000 anal sis resecase t&es for the 0.. n4 mos: linitina break ~ size.
A comparizn of in analysis response can be found in Table 1 (copy attached).
Supporting analysis for sate operation in the SLO mode can be found in' the Systenatic Evaluet% program (SEP) review (reference 5).
Although this review did not address the acceptability of the GE ECCS analysis, which prompted this review, several other areas of concern were addressed.
A major point was that SLO will not affect the reactor coolant flow distri-Sution.
The coolant flows through two inlet nozzles (one Der loop) which are 72 degrees apart on the vessel lower head.
The flow entering through each' nozzle impinges on a diffuser plate (one plant per nozzle). A flow diffuser baffle connected to the core support plate surrounds the fuel channel support tubes and causes the pressure at the inlet to the core support tubes 'a be relatively uniform.
The fact that the vessel entrance region acts as a plenum has been supported by test (" Core Performance and Transient Flow 7esting - Bin Rock point Boiling Water Reactor," GEAP-4496, July 1965, USAEC contract AT (04-3)-361).
The test showed that the frictional pressure drop betwaen the vessel nozzles and the support tube inlets to be nearly 5 times the velocity head in the support tubes.
Instrumented fuel assembly measurements l
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t 4 during forced-circulation tests (Figure 4-7 of the above reference) have shown relative assembly power to be insensitive to the number of loops in operation, further indicating that the relative flow to the assemblies is not substantially affected by the number of loops in operation. When considering the high losses due to flow resistance caused by the orifices in the assemblies, a small pressure difference in the lower plenum at the support tube entrance elevation should have a negligible effect on the core flow distribution.
The SEP review also concluded that the acceptability of the SLO is contingent upon the licensee's agreement to (1) include in a procedure for N-1 loop opera-tion a statement that the bypass and isolation valves in the inactive loop be closed during N-1 operaticc., (2) physically lock-out power to the inactive pump, and (3) incorporate the MAPLHGR limits for N-1 loop operation in the Technical
.Speci fi ca tions. By letter dated September 3,1981, the licensee stated that items (1) and (2), above,have been included in the plant procedures. This amendment would incorporate MAPLHGR limits for SLO into the Technical Specifications.
Based on the references presented, the NRC staff agrees with the licensee that the GE SLO ECCS analysis will adequately represent the behavior of EXXON fuel elements-in a LOCA situation. Based on the supportive analyses, the NRC staff concludes that SLO is a safe means of reactor operation.
4.0 ENVIRONMENTAL CONSIDERATION
.~.a.
We have determined that the amendment does not authorize a change in effluent tyoes or total arcunts nor an increase in erzier lev 11 and aill not resul t i-any s i gni ficant enc ironr.er tal impact.
En
'g tte th'c deternination, c.e have further. concluded that the amendment ir.voives cr action which is insignificant from the standpoint of environmental impact and pursuant to 10 CFR 551.5(d)(4) that an environmental impact statement or negative declaration and environmental inpact appraisal need not be prepared in connection with the issuance of this amendment.
5.0 C0]itipSIONS We have concluded, based on the conriderations discussed above, that: (1) because the amendment does not involve a significant increase in the pro-bability or consequences of accidents previously considered and does not involve c significant decrease in a safety margin, the amendment does not involve a significant hazards consideration, (2) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (3) such activities will be con-ductec in compliance with the Commission's regulations and the issuance of this amendment wil' not be ininical to the common defense and security or to the health and safely of the public.
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(1)
" Big Rock Point Single-Loop Operation Loss-of-Coolant Accident Analysis for General Electric Fuel in Conformance with 10 CFR 50 Appendix K (Non-Jet Pump Boiling Water Reactor)," March 31, 1977.
4 (2). Safety Evaluation Report from D. Zieman (NRC) to Consumers Power, June 4, l.o 7 6.
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(3)
Letter from G. C. Winthrow (Consumers Power) to D. Crutchfield, July 22, 1951.
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(4)
Letter from G. C. Winthrow (Consumers Power) to D. Crutchfield, June 19, 1981.
j (5)
Letter from D. Ziemann (NRC) to D. Bixel (Consumers Power), August 9,1979.
j Dated:
September 21, 1981
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- Attached: Table 1 I". J >
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implies information not readily availablo, e
(1) Time at which quality at hot nodo (coro midplano) goes to 1.0.
ft result in HDS actuation. HDS hiowdown is prolonged in the Exxon 2
(2)Dreak smaller than about 0.1analysos versus the GE analysos becauso Exxon assumod only thrpo operahlo blowdown paths whoroas CE a ssumed i'our.
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