ML20205C743
| ML20205C743 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 09/16/1985 |
| From: | Opeka J, Sears C NORTHEAST NUCLEAR ENERGY CO., NORTHEAST UTILITIES |
| To: | Thompson H Office of Nuclear Reactor Regulation |
| References | |
| A05034, A5034, GL-85-12, NUDOCS 8509230189 | |
| Download: ML20205C743 (6) | |
Text
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((*,',[",,[',"g (203) 665-5000 September 16,1985 Docket No. 50-423 A05034 Mr. Hugh L. Thompson, Jr., Director Division of Licensing Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D. C. 20555
Reference:
(1)
H. L. Thompson letter to All Applicants and Licensees with Westinghouse Designed Nuclear Steam Supply Systems, dated June 28,1985 (Generic Letter No. 85-12).
(2)
B. 3. Youngblood letter to W. G. Counsil, Safety Evaluation Report for Millstone 3, dated August 2,1984.
Dear Sir:
Millstone Nuclear Power Station, Unit No. 3 Response to Generic Letter 85-12 Reference (1) provided the Staff's safety evaluation report on the Westinghouse Owners Group (WOG) submittals on reactor coolant ptmp trip methodology which were made in response to Generic Letter 83-10c. The Staff concluded that the methods employed by the WOG in justifying manual reactor coolant pump trip are consistent with the criteria provided in Generic Letter 83-10c and are, therefore, acceptable. It was determined that individual applicants / licensees could implement the WOG reactor coolant pump trip methodology provided that they provide certain plant specific information which was identified in Section IV of Reference (1) and that this information was found acceptable by the Staff.
Northeast Nuclear Ener y Company (NNECO) hereby provides the information requested in Reference (g),Section IV for Millstone Unit No. 3.
1 Please also note that this information also responds to Confirmatory item #65 which was contained in Reference (2).
A.
Determination of RCP Trip Criteria 1.
Identify the instrumentation to be used to determine the RCP trip set point, including the degree of redundancy of each parameter signal needed for the criterion chosen.
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. Response:
Reactor Coolant System (RCS) pressure has been selected as the parameter to be monitored for determining when the Reactor Coolant Pumps (RCP) should be tripped. Milistene Unit No. 3 has two wide range (0-3000 psia) pressure channels which operators will monitor to determine if tripping the Reactor Coolant Pumps is necessary.
the instrumentation uncertainties for both normal and Identify 2.
adverse containment conditions. Describe the basis for the selection of the adverse containment parameters. Address, as appropriate, local conditions such as fluid jets or pipe whip which might influence the instrumentation reliability.
Response
The RCS wide range pressure transmitters are located inside of the containment, but outside of the missile shield. Following a Design Accident, these transmitters would be subjected to high Basis temperature, high humidity, high pressure, and high radiation and are qualified for such conditions. Because the transmitters are located outside of the missile shield, pipe whip and fluid jets are not a concern.
In determining the RCP trip setpoints, the effects of instrument accuracy, instrument drift, temperature, and radiation from adverse containment conditions have been considered.
The emergency operating procedures-include manual RCP trip setpoints for both normal and adverse containment conditions.
3.
In addressing the selection of the criterion, consideration to uncertainties associated with the WOG supplied analyses values must These uncertainties include both uncertainties in the be provided.
computer program results and uncertainties resulting from plant specific features not representative of the generic data group.
If a licensee determines that the WOG alternative criteria are marginal for preventing unneeded RCP trip, it is recommended that a _
more discriminating plant-specific procedure be developed.
For use of the NRC-required inadequate-core-cooling.,
- example, instrumentation may be useful to indicate the need for RCP trip.
Licensees should take credit for all equipment (instrumentation) available to the operators for which the licensee has sufficient confidence that it will be operable during the expected conditions.
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Response
A' review of the FSAR Chapter 15 accident analyses indicates that for most non-LOCA accidents, RCS pressure does not f all below the RCP manual trip pressure. Three accidents will cause the RCS to depressurize below the RCP trip setpoint. They are:
- 1. Feedwater Line Break
- 2. Steamline Break
- 3. Inadvertent Opening of a Steam Generator Relief or Safety Valve The first two accidents were evaluated both with and without offsite power. The third accident was evaluated only with offsite power available. It is however, bounded by the steamline break.
Therefore, since the limiting events were evaluated assuming offsite power is unavailable, tripping the RCPs will not affect the consequences of the accident analyses reported in the FSAR.
B.
Potential Reactor Coolant Pump Problems 1.
Assure that containment isolation, including inadvertent isolation, will not cause problems if it occurs for non-LOCA transients and accidents.
- a. Demonstrate that, if water services needed for RCP operations are terminated, they can be restored fast enough once a non-LOCA situation is confirmed to prevent seal damage or failure.
- b. Confirm that containment isolation with continued pump operation will not lead to seal or pump damage or failure.
Response
During non-LOCA accident conditions, isolation of water systems to support RCP operation will not occur. Seal injection water to the RCP seals is maintained continuously by the charging system during all postulated accident situations with the exception of. total loss of AC power.
Reactor Plant ' Component Cooling Water (RPCCW) is maintained during non-LOCA accident situations until the containment high-3 pressure setpoint is reached causing a Phase B isolation. Because a containment high-3 pressure condition indicates a large LOCA or steamline break in containment, the RCPs should be tripped and maintenance of RPCCW to the RCPs is not necessary.
2.
Identify the components required to trip the RCPs, including relays, power supplies and breakers. Assure that RCP trip, when determined to be necessary, will occur. If necessary, as a result of the location i
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of any critical component, include the effects of adverse containment conditions on RCP trip reliability. Describe the basis for the adverse containment parameters selected.
Response
In order to trip an RCP, the 6.9 kV supply breaker to the pump must be opened. The breaker can be operated remotely from the control room or locally at the RCP breaker cubicle. As a backup to the RCP supply breakers, the 6.9 kV buses can be de-energized as they supply no other safety-related loads.
The containment penetration overcurrent protection devices can also serve as a backup to the main RCP breakers. Adverse containment conditions will not affect the operation of the RCP breakers.
C.
Operator Training and Procedures (RCP Trip) 1.
Describe the operator training program for RCP trip. Include the general philosophy regarding the need to trip pumps versus the desire to keep pumps running.
Response
The Millstone Unit No. 3 cold license training program includes specific training on manual RCP trips as part of the Mitigating Core Damage class. Items covered include: advantages of keeping the pumps running, the possibility of uncovering the core during a small break LOCA after stopping the pumps, the effects of pump restart on core two-phase level and RCS two-phase flow.
In addition to classroom training, the operator receives training in the use of procedures that require manual RCP trip on the Millstone Unit No. 3 simulator and during classroom training on the procedures.
In the future, operator training on RCP manual trip criteria will be performed as part of the Operator Hot License Training Program and Licensed Operator Requalification Program.
2.
Identify those procedures which include RCP trip related operations:
(a)
RCP trip using WOG alternate criteria (b)
RCP restart (c)
Decay heat removal by natural circulation (d)
Primary system void removal (e)
Use of steam generators with and without RCPs operating (f)
RCP trip for other reasons
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1 Response:
Plant procedures which cover RCP start and stop operations are listed in Attachment 1.
We trust that this information satisfactorily responds to Generic Letter 85-12 and also closes SER Confirmatory item //65.
Very truly yours, NORTHEAST NUCLEAR ENERGY COMPANY et. al.
By Northeast Nuclear Energy Company Their Agent d.k.b
- 3. F. Opeka Senior Vice President By: C. F. Sears Vice President STATE OF CONNECTICUT )
) ss. Berlin COUNTY OF HARTFORD
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Then personally appeared before me C. F. Sears, who being duly sworn, did state that he is Vice President of Northeast Nuclear Energy Company, an Applicant herein, that he is authorized to execute and file the foregoing information in the name and on behalf of the Applicants herein and that the statements contained in said information are true and correct to the best of his knowledge and belief.
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ATTACHMENT I PLANT PROCEDURES WHICH COVER RCP START AND STOP OPERATIONS a
OP-3201 RCS Heatup OP-3208 RCS Cooldown OP-3301 Reactor Coolant Pump E-0 Reactor Trip and Safety Injection E-1 Loss of Reactor or Secondary Coolant E-3 Steam Generator Tube Ruptures ES 0.2 Natural Circulation Cooldown ES 0.3 Natural Circulation Cooldown with a Steam Void in the Vessel (with RVLMS)
ES 0.4 Natural Circulation Cooldown with a Steam Void in the Vessel (without RVLMS)
ES 1.1 SI Termination ES 1.2 Post-LOCA Cooldown and Depressurization i
ES 3.2-Post-SGTR Cooldown using Blowdown ECA-2.1 Uncontrolled Depressurization of all Steam Generators ECA-3.1 SGTR with loss of Reactor Coolant Subcooled Recovery Desired i
ECA-3.2 SGTR with loss of Reactor Coolant Saturated Recovery Desired FR C.1 Inadequate Core Cooling FR C.2 Response to Degraded Core Cooling FR H.1 Loss of Secondary Heat Sink FR I.3 Response to Vold in the Vessel l
AOP 3561 Loss of Reactor Plant Component Cooling Water
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