ML19269C802
| ML19269C802 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 02/05/1979 |
| From: | Gilleland J TENNESSEE VALLEY AUTHORITY |
| To: | Ippolito T Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 7902120207 | |
| Download: ML19269C802 (2) | |
Text
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TENNESSEE VALLEY AUTHORITY CH ATTANOOGA. TENNESSEE 374o1 500C Chestnut Street Tower II FEB 5 1979 Director of Nuclear Reactor Regulation Attention:
Mr. Thomas A. Ippolito, Chief Branch ho. 3 Division of Operating Reactors U.S. Nuclear Regulatory Commission Washington, DC 20555
Dear Mr. Ippolito:
In the Matter of the
)
Docket No. 50-259 Tennessee Valley Authority
)
This is in response to a verbal request from your staff for information in support of our applicatica for a license amendment to permit cycle 3 operation of Browns Ferry Nuclear Plant unit 1 with operating credit allowed for the installed end-of-cycle recirculation pump trip (RPT) system.
Enclosed is justification that a reduction in the reactor power level to less than 85 percent in the event of a degraded conditi'n of the PPT system will ensure safe operation.
Very truly yours, s
j2 hJ2(ilamf
- 3. E. Gilleland Assistant Manager of Power Enclosure
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s 7 9 0 212 0 2 en An Equal Opportunity Employer
t JUSTIFICATION FOR OPERATION AT 85 PERCENT POWER IN THE EVENT THAT BOTH RECIRCULATION PUMP TRIP SYSTEMS ARE INOPERABLE Performance studies of a BWR at reduced power and flow shows that the delta-CPR for pressurization events (load rejection without bypass, etc.) can be reduced to 60 percent of the value based on the 100 percent power flow state when the core power has been reduced to approximately 85 percent by flow control.
These studies were performed for several transient events including the Load Rejection Without Bypass using standard computer program and licensing con-servatisms. The study did not include recirculation pump trip (RPT) but other studies relating improvements with RPT have shown that RPT reduces delta-CPR to approximately 60 percent of that withcut RPT.
The study was performed at end-of-cycle conditions (i.e., all rods out). At other operating conditions (lesser exposures, etc.) events such as Rod Withdrawal Error which are not affected by the operation of the RPT system would be limiting. Thus, reducing core power to 85 percent without RPT would result in a trade-off not requiring MCPR operating limit changes.
Additional conservatism will also appear in the form of higher operating Mini-mum Critical Power Ratio when the core power is reduced. This additional conservatism is worth approximately 7 percent at the reduced core power and flow described previously. Thus, should the unlikely pressurization event (Load Rejartion Without Bypass) actually occur, the safety limit MCPR surely would not be violated.
O
.-lease note that the attached letter dated January 24, 1979, submitted b'y Northeast Nuclear Energy Company, replaces their letter dated December 18,1978 (Acce;sion No. 7812280137),
which is now deemed to' contain proprietary information.
4 Those recipients identified oelow should take appropriate action to control and handle the december 18, 1978 letter a proprietary:
ORB #4 BC I&E Reg File Core Perf Br Hanauer Engr Br AD Sys, proj Plant Sys Br Reac Sfty Br Effl Trt Sys EEB ACRS Brinkman TERA DELD HSmith THE FOLLOWING RECIPIENTS SHOULD IMMEDIATELY DESTROY THEIR COPIES OF THE DECEMBER 18, 1978 LETTER:
NRC PCR L PDR NSIC If you have any questions, please call Roberta Ingram, X 27435.
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