ML20054F090
| ML20054F090 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 06/10/1982 |
| From: | Vincent R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Crutchfield D Office of Nuclear Reactor Regulation |
| References | |
| TASK-15-01, TASK-15-1, TASK-RR NUDOCS 8206150207 | |
| Download: ML20054F090 (4) | |
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O O consumers Power company General O ff 6ces: 212 West Michigan Avenue Jackson, MI 48201 e (517) 70s-0660 June 10, 1982 Dennis M Crutchfield, Chief Operating Peactors Branch No 5 Nuclear Reactor Regulation US Nuclear Regulatory Commission C
Washington, DC 20555 DOCKET 50-155 - LICENSE DPR-6 BIG ROCK POINT PLANT - SEP TOPIC XV-1, Decrease in Feedwater Temperature, Increase in Feedwater Flow and Increase in Steam Flow.
By letter dated March 4, 1982, the NRC issued its evaluation of SEP Topic XV-1 for the Big Rock Point Plant. This evaluation was based on an SAR submitted to the NRC by Consumers Power Company letter dated July 15, 1981. Consumers Power Company has reviewed the staff evaluation and offers the following additional information to address unresolved staff concerns.
With respect to the staff evaluation of the increase in feedwater fit s transient, a concern was raised because the Consumers Power Company analysis of the event assumed that the non-safety turbine bypass system was operable to mitigate the effects of the transient. The evaluation went on to state that since the turbine bypass system is not safety related, either the event would have to reanalyzed to show the criteria to be sati;*'ted without bypass, or a surveillance program should be instituted for the bypass system.
Consumers Power Company has reanalyzed the event using the same codes as before with the same model except that the bypass system is assumed in-operable throughout the event. As before, the high power trip occurs at 14.1 seconds into the transient, and the minimum reduction in MCPR is 0.11, which is identical to the analysis with tne bypass system operating.
The ma:(imum pressure of 1416.5 psia was at 215 neconds af ter the start of the transient and is reduced after the peak by che rapid addition of cold feed water. The peak pressure is less than the settings of the relief valves and approximately 40 psi greater than the original analysis.
Attached is a plot of the reactor pressure vs,. time for the transient.
The maximum reactor power of 125.6% occurs at 14.5 seconds into the transient as it did before, p@6 8206150207 820610 DR ADDCK 05000155 PDR
e D M Crutchfield, Chief 2
Big Rock Point Plant' SEP TOPIC XV-1 June 10, 1982 Therefore, the analysis shows the criteria for MCPR and maximum coolant pressure are satisfied even with the turbine bypass valve failed closed.
During performance of this analysis, some errors were noted in the earlier Consumers Power Company analysis submitted for the increase in feedwater flow transient. The errors are minor and will not effect the HRC evaluation. Corrections to be made are as follows: The turbine bypass valve would begin to open at 14.75 seconds and not 14.2 seconds.
The maximum reduction in MCPR occurs at 14.5 seconds and not 15.5 seconds.
The maximum reactor pressure is 1376 psia at 16.75 seconds instead of 1386 psia. Attached is a corrected Table 3.2.1 for the original analysis and a similar table for the analysis without the bypass system operable.
The change in the times for the bypass valve opening and reduction in MCPR explains why the reduction in CPR is the same for both cases.
This is because the bypass valve would not operate until after the maximum reduction in MCPR has already occurred.
We truct that this information resolves any remaining concerns for topic XV-1.
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Robert A Vincent Staff Licensing Engineer CC Lirector, Region III, USNRC HRC Resident Inspector-Big Rock Point l
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REVISED TABLE 3 2.1 (CPCo Letter of July 15,1981)
Sequence of Events Increase in Feedwater Flow with Bypass Feedwater Regulator at Maximum Demand t=
0 sec.
(372lbm/sec)
Reactor Trip on High Core Power t = 14.1 sec.
(Coincident Turbine Trip)
Maximum Reactor Power (125.6%)
t = 14.5 sec.
Maximum Reduction in MCPR t = 14.5 sec.
Turbine Bypass Valve Begins to Open t = 14.75 sec.
Maximum Reactor Pressure (1376 psia) t = 16.75 sec.
Sequence of Events Increase in Feedwater Flow with Bypass Feedwater Regulator at Maximum Demand t=
0 sec.
(372lbm/sec)
Reactor Trip on High Core Power t = 14.1 sec.
(Coincident Turbine Trip)
Maximum Reactor Power (125.6%)
t = 14.5 sec.
MaxLawn Reduction in FCPR t = 14.5 sec.
Maximum Reactor Pressure (1416.5) t = 21.5 sec.
25/05/82 RIAA FWFIN BIG ROCF PT.
==FEEDWArE-FLOW INCREASE.
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10 15 20 25 30 35 40 TIME (SEC)
FIGUhr.; 1.
Reactor Vessel Pressure versus Time for Feedwater Flow Increase Uithout Turbine Bypass.
Transient Initiated at 1 Second.
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