ML19269C164
| ML19269C164 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 01/23/1979 |
| From: | Gilleland J TENNESSEE VALLEY AUTHORITY |
| To: | Ippolito T Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 7901290259 | |
| Download: ML19269C164 (4) | |
Text
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TENNESSEE VALLEY AUTHORITY CH ATTANOOGA. TENNESSEE 37401 500C Chestnut Street Tower II JAN 231979 Director of Nuclear Reactor Regulation Attention:
Mr. Thomas A. Ippolito, Chief Branch No. 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
)
Please refer to your letter to Hugh G. Farris of January 16, 1979, concerning the logic design of the recirculation pump trip (RPT) modification of which TVA has requested NRC approval in accordance with 10 CFR Part 50.59.
Enclosed is information requested by your staff in a January 17, 1979, meeting concerning the RPT desi m which we hope will alleviate your concerns. The enclosed informatian supplements m' letters to you of December 5 and 14, 1978, and January 9, 19i9. Your expeditious review and approval of the RPT design would be greatly appreciated. Without apprcval we expect to be limited to approximately 86 percent power beginning about January 30, 1979.
Very truly yours,
/),
/
i J. E. Gilleland Assistant Manager of Power Enclosure
@\\
7901290359 An Equal Opportunity Employer
BROWNS FERRY UNIT 1, CYCLE 3 RESOLUTION OF CONCERNS OF NP.C REVIEWER EXPRESSED IN JANUARY 17, 1979, MEETING BETWEEN NRC AND TVA Concern 1 Describe the preoperational, startup, and pc ' odic testing to be done on the RPT system.
Response 1 Preoperational Testing A comprehensive functional test of the RPT system is performed to confirm the correct installation of the integrated system prior to startup.
This testing includes a check of all relay logic combinations and several breaker trips.
Startup Testing The startup testing is performed in two parts. A turbine trip from low power with RPT initiation is done to establish the delay time from beginning of turbine valve motion to the RPT breaker trip.
Secondly, a two pump trip (RPT) is performed from full flow to measure the actual flow coastdown rate.
This coastdown rate, with the delay time, is confirmed to be less than the rate assumed in the transient calculations.
Periodic Testing A.
Once per cycle breaker functional This test has not yet been formalized.
W anticipate tripping both breakers by manually completing the existing logic.
B.
Monthly Logic Testing The RPT monthly logic testing is done in parallel with the monthly RPS surveillance.
Control Valve Logic _
Each control valve is individually closed. RPT relay contact status lights 5A-D515X are checked, and the it.'ividual RPT relays are visually monitored for proper operation.
It is not necessary to bypass any RPT systems for this test.
Stop Valve Logic The i+1r stop valve pairs that drive the auto-scram channels are closed until they pick up the 10%
closed switches.
Two of the above combinations also complete the RPT logic, as evidenced by the energization of test coil 5A-K32A(B) which alarms as the "RPT initiate" annunciator.
It is necessary to place the individual RPT system in " bypass" briefly to prevent actual tripping of the recirculation pumps.
At least one RPT systum will always be in service.
Periodic Response Time Testing As agreed with regard to this subject, we commit to respond within 6 months.
Concern 2 Verify that the RPT has no effect on the RWE analysis.
Response 2 RPT has no effect on the RWE analysis, and is not assumed to operate.
Concern 3 Verify that RPT is required only for closure of all four stop or control valves?
Response 3 The RPT improvement is designed to operate for the limiting case of the turbine / load reject without bypass, i.e.,
simultaneous closure of all four stop/ control valves.
Failure of one or more valves to closure maintains an equivalent steam bypass path, thus significantly alleviating ti resultant pressure transient.
In this case, RPT in intion is not required.
Concern 4 In referencing NEDO 24119, TVA should state an exception to the implication that the RPT is entirely fail-safe.
Response 4 TVA takes exception to the referenced NEDO for the following reasons.
It is true that relays used by the RPT logic are of a fail-safe logic, i.e.,
trip on loss of electrical power to individual relays.
Ilowever, loss of control power to a particular RPT board will result in the failure of that individual system. Therefore, individual RPT boards are not considered entirely " fail-safe." However, as noted in previous responses, each RPT board has independer..
power supplies.
Concern 5 In the FWCF analysis, the turbine is assumed to trip as a result of high w,'.ter level.
What are the consequences of an earlier or later turbine trip than that assumed in the analysis?
Response 5 The present design and licensing basis assumes a turbine trip initiated from high water level followed by a scram, recirculation pump trip and opening of the turbine bypass valves.
In the unlikely event of no turbine trip (multiple failures are required) from high reactor water level, turbine trip would result from high moisture separator level or tarbine vibration. An increase in the present calculated Jelta CPR for the license basis transient of about 0.02 is estimated to result. Thus, we believe the license basis specified in NED0-24136 remains appropriate.
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