ML19350E574
| ML19350E574 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 06/19/1981 |
| From: | Withrow G CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Crutchfield D Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8106230295 | |
| Download: ML19350E574 (5) | |
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kr u f Company General Offtsee: 212 Wert Michigan Avenue, Jackson, Michison 40201 * (517) 795M50 June 19, 1981 t""
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Director, Nuclear Reactor Regulation ggg1i, y Att Mr Dennis M Crutchfield, Chief E
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US Nuclear Regulatory Commission g
Washington, DC 20555 g
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DOCKET 50-155 - LICENSE DPR BIG ROCK POINT PLANT -
ECCS OPERATING LIMITS -
SINGLE LOOP OPERATION NRC letter dated June 9, 1981 provided Amendment No 44 ;o Facility Operating License No DPR-6 for the Big Rock Point Plant. This amendment authorized a change in reactor operating limits for two reactor coolant recirculation loop operation and noted that the NRC Staff evaluation of single recirculation loop operation was continuing.
A telephone discussion between the Staff and Consumers Power Company on June 17, 1981 provided verbal answers to two questions informally received from the Staff. Per Staff request, Attachment 1 to this letter is provided to document the questions and our responses.
The current restrictions imposed by NRC letter dated June 9, 1981 affect our ability to operate with only one recirculation loop operable.
It is requested that your immediate attention be placed upon resolution of your single loop operation concerns so that the Technical Specification changes as requested by our February 25, 1980 submittal can be fully implemented eliminating the current restrictions.
G C Withrow (Signed)
G C Withrow Senior Licensing Engineer CC JGKeppler, USNRC NRC Resident Inspector oc0681-0315a-43 8106280 W P
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7 ATTACHMENT 1 ECCS Operating Limits - Single Loop Operation NRC Question No 1 Your technical specification change request on ECCS operating limits provided by letter dated February 25, 1980 makes reference to General Electric Company Report dated March 31,1977, " Big Rock Point Plant 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.)" This report describes the results of the single-loop analysis for MAPLHGR limits for the General Electric fuel used in the Big Rock Point plant.
Based on the results of this analysis, MAPLHGR limits for two-loop operation were reduced by five percent for GE fuel types for operation with one recirculation loop. A more recent generic licensing topical report (NED0-20566'-2, Revision 1, dated July, 1978) dealing with Loss-of-Coolant Analysis for one recirculation loop out of service has been submitted by General Electric Company. The staff requests that a discussion of the applicability of the more recent analysis method to Big Rock Point be provided. The discussion should include any expected differences in the results of the prediction of the MAPLHGR reduction identified in the Technical Specification Change request. Other significant LOCA analysis parameters, such as hot node uncovery, reflood time, time to boiling transition and peak cladding temperature should also be addressed.
Response
Consumers Power Company does not have access to NEDO-20566-2, Revision 1.
However, discussions with T W Craig of General Electric revealed that the methods used in the generic analysis contained in NED0-20566-2 were the approved Appendix K ECCS models as described in NED0-20566 with one exception.
The generic analysis for one loop out of service assumed almost instantaneous flow stagnation and boiling transition (ie, no credit was taken for flow coastdown as allowed by the approved methods for all loops in service). For the jet pump BWR with all loops in service, boiling transition typically takes place in a 6-8-se.cond time period following the DBA.
The Big Rock Pcint (ERP) Plant specific single loop operation LOCA analysis performed by GE also used the approved Appendix F LOCA models. No credit was taken for flow coastdown in the LOCA analysis for single loop operation. The same assumption was also made in the analysis for both loops in operatien.
The time to boiling transition was calculated in both analyses using the GE dryout time correlation as described in Section I.C.4 of NED0-20566. Dryout times on the order of 1.0-1.5 seconds were calculated for single loop operation. This compares to dryout times of 1.5-2.0 seconds for both loops in operation.
It should be noted that the shorter dryout time in the one loop operation case is not the major reason for the 5% reduction in MAPLHGR that was specified by our February 25, 1980 submittal. As discussed in the response to Question 2, the 5% reduction in MAPIRGR is primarily due to the significantly earlier core uncovery that occurs in the one loop operation case.
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One observation mado based on the foregoing discussion is that the effect of.
N-1 loop operation on MAPLHGR linaits may be somewhat greater for the jet pump BWRs than for BRP. This is due to the fact that the jet pump BWRs take credit for a relatively lengthy period of nucleate boiling with all loops in service but take essentially no credit for nucleate boiling with one loop out of service; wheraas BRP takes credit for very little nucleate boiling in either case.
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j; NRC Question No 2 Your, technical specification change request on ECCS operating limits provided by letter dated February 25, 1980 proposes that the MAPLHGR limits for single loop operation be reduced by 10 M rcent for Exxon fuel types. No specific analysis has been provided to - ;ify this reduction in MAPLHGR limits. The 8
staff requires that additional aiscussion be provided to justify the conclusion that the MAPLHGR for Exxon fuel is relatively insensitive te flow reduction under single loop operation.
R_esponse e
Key system response parameters are compared on the attached table fer the LOCA anlayses performed by Exxon and GE.
Conclusions to be drawn based on this comparison are:
1.
Blowdown times, times of rated core spray flow, and times of core midplane uncovery compare well between the GE and Exxon analyses for the case with
~two loops in operation. Exxon predicts slightly slower depressurizations
.for breake larger than about 1.0 ft" and slightly faster depressurizations for breaks smaller than about 1.0 ft8 Core spray times compare in a similar manner. For the limiting break in the Exxon analyses, the core midplane uncovery time is nearly identical to what would be expected had GE analyzed the same case.
2.
Lepressurization rates are about the same for the GE and Exxon one-loop and two-loop analyses. However, core uncovery times are much earlier in the GE one-loop case. This is due to the fact that the break, which is at the discharge of the isolated pump, is fed only from the reactor side 7f the system. The earlier core uncovery time results in the 5% reduction in MAPLHGR for single loop operation which was specified for GE fuel.
3.
Considering the similarity of the Exxon and GE analyses in the case with two loops operating, it is reasonable to expect that Exxon would predict a similar system response to GE if it were asked to analyze LOCAs with one loop in service. Having not analyzed the case with one loop operating, it is reasonable to require a greater MAPLHGR reduction for single loop operation for Exxon fuel. A 10%* reduction was proposed to account for the greater uncertainty in the case of Exxon fuel. A 15% to 20% reduction would be acceptable from the operations point ;f view as other fuel limits (ie, MCHFR) are typically much more limiting coring single loop operation.
- The 10% reduction in MAPLHGR for single loop operation was implemented in June 1977 when the GE analysis was received by CP Co - See LER R0-77-20 submitted on June 8, 1977.
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1 QOMPARISOtt OF KEY SYST[M RESP 081}E PARAMETERS i
AS PREDICIED BY LV OM.AMD GE APPEteDix k LOCA MODELS 1
~l Time (Sec)
Cold Leg
- f Brea k Low Reactor Pressure (200 Psia)
Rated Core Soray Flow Core Midolane Uncoverv Exxon GE GE Exxon GE GE Exxon GL.
.l Sizg1 IFt (2 Loopsl (2 Loop _sJ f1 Locp_1 (2 Loops)
(2 Loopsl f1 Loool (2 LogpM 12 Locos]
[1 Loom) s 7.1 20.4 f
5.
3.926 26.9 3.53 11.9 4.0 27.7 12.
1.6 17.2 6.1-1.0 20.4 21.5 20.
35.4 36.9 35.4 20.6 10.8
.50 36.3 40.
40.
51.3 55.1 64.
13.6 71.
-23.(1) 54.
61.5
.375 46.5 29.9 19.4
.25 67.9 75.
75.
85.6 98.2 103.
t>2. 2 48.9
.10 101.(2)
";3.
I t:0.
189.
156-158.
l
- Impiles case not analyzed.
- Implies information not readily available.
(1) Time at which quality at hot node (core midplane) goes to 1.0.
ft result in RDS actuation. RDS blowdown is prolonged in the Exxon (2) Break smaller than about 0.1
/ersus the GE analyses because Exxon assuned only three operablo blowdown paths whereas analyset GE assumed four.
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