ML18139A374
| ML18139A374 | |
| Person / Time | |
|---|---|
| Site: | Surry, North Anna  |
| Issue date: | 06/11/1980 |
| From: | Sylvia B VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| IEB-80-12, NUDOCS 8006300235 | |
| Download: ML18139A374 (5) | |
Text
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e VIRGINIA ELEC'l"R.IC AND POWER COMPANY RrcHMoND, VlHG'lll'.IA *23261 r, : I I '! f. I I,*;:
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June 11, 1980 Mr. James P. O'Reilly, Director Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission Region II 101 Marietta Street, Suite 3100 Atlanta, Georgia 30303
SUBJECT:
I. E. BULLETIN 80-12
Dear Mr. O'Reilly:
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Serial No. 432/050980 NO/RMT:ms~
Doc~et.*No~
50-338 50-339 License Nos. DPR-32 DPR-37 NPF-4 NPF-7 This letter is in response to IE Bulletin 80-12, "Decay Heat Removal System Operability."
Our response for Surry Power Station Unit Nos. 1 and 2 and North Anna Power Station Unit Nos. 1 and 2 is attached.
If you have any questions or require additional information, please contact this office.
Attachment Very truly yours,
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B. R. Sylvia Manager-Nuclear Operations and Maintenance cc:
Director, Division of Reactor Operations Inspection NRC Office of Inspection and Enforcement Washington, D. C.
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e RESPONSE TO IE BULLETIN 80-12 NORTH ANNA POWER STATION UNITS 1 AND 2 SURRY POWER STATION UNITS 1 A1'.i""D 2 Attachment Page 1
- 1.
The. circumstances and sequence of events described in Enclosure 1 of the IEB 80-12 for the Davis-Besse Unit 1 Power Station were reviewed for applicability to the operation of North Anna Units 1 and 2 and Surry Units 1 and 2.
The review revealed the North Anna and Surry core decay heat removal systems~ refer:red to
- as the Residual Heat Removal Systems (RHR), to be fundamentally different from the Davis-Besse Unit 1 design.
Contrary to the Davis-Besse design, the North Anna and Surry RlIR systems are separate fluid systems from the Low Head Safety Injection Systems.
RHR is utiliz-ed as a control system to allow normal regulated cooldown of the Reactor Coolant system below 350°F.
The Safety Injection (SI)
System is independent and provides emergency protection to the core to prevent overheating in the event reactor coolant is lost.
The functional separation of the RHR System and SI System in the North Anna and Surry designs guards against the loss of RHR suction resulting from~ spurious SI system failure similar to the Davis-Besse event.
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- 3.
A review of past degradation events from North Anna and. Surry reveals no event similar to the Davis-Besse incident.
However, as described below, there have been reported occurrences where the RHR System was temporarily inoperable.
The RlIR System is designed to be* a highly reliable fluid system.
The system contains two RlIR pumps which are normallypowered from separate emergency power supplies.
Each pump has capability of being manually tied to the redundant emergency power supply.
Addi-tionally, two heat exchangers are available with cooling supplied from emergency powered component cooling water pumps.
Past perfor-mance of pumps and heat exchangers has been reliable.
In other parts of the RHR System, valve packing leaks have caused interrup-tions; however, these failures have been few and random in nature.
In general, mechanical and electrical reliability of the system has been satisfactory.
With one exception, the RHR System instruments and controls func-tion with adequate reliability to position valves, warm up the system, and regulate core decay heat removal.
Controls for the series-connected inlet valves are interlocked with reactor coolant pressure channels to close er prevent opening of the system, there-by protecting it from overpressurization.
This feature can and has resulted in undesirable spurious isolation of the RIIR System.
It is, however, the design objective of the control system to isolate or to maintain isolation of the RHR System.
Therefore, a failure such as a blown fuse results in conservative protective action.
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- 4.
Attachment Page 2 Current operating procedures provide adequate safeguards for redundancy while operating or in a
In an intermediate or cold shutdown condition, Technical Specifications and operating procedures require only one RHR subsystem to be operable and there-fore are inadequate for safeguarding against loss of redundancy required by the Bulletin.
During a refueling, Technical Speci-fications and operating procedures require one RlIB Subsystem in operation with permission to remove it from service for up to one hour per eight hours during the performance of core alter:ations.
Consequently, during refueling, procedures and Technical Specifi.-
cations are inadequate to safeguard against loss of redundancy required by the Bulletin.
Technical Specifications do, however, require a boron injection flow path to be operable.
The additional source of borated water meets diversity requirements of the Bulle-tin in lieu of maintaining two operable RHR Subsystems during refueling.
Normally, it is during refueling that the Reactor Coolant System is opened; however, maintenance may be performed other than removing the head in cold shutdown, which requir~s draining* reactor coolant to the centerline of the vessel nozzles.
This makes the steam generators URavailable to remove heat as a diverse source.
For this condition, diversity requirements are met by the operability of the boron injection flow path.
Other means of backup are also available during cold shutdown by RWST recircula-tion utilizing the low head safety injection pumps and during refueling by use of the refueling purification system and the spent fuel pit cooling system..
In summary, operating procedures and Technical Specifications for all modes are adequate for redundancy or diversity requirements of the Bulletin except for RHR operation in an intermediate or cold shutdown condition.
In these conditions, meeting redundancy requirements is impractical if RHR maintenance activities are to be performed.
Therefore, procedures require revision to ensure a diverse method of residual heat removal if.one Rlffi Subsystem.is inoperable.
Operating procedures will. be changed to require at least one operable steam generator capable of removing heat while operating in an intermediate or cold shutdown condition with one RHR subsystem inoperable or at least one Low Head SI pump (and the RW.ST) in the train opposite the R1IR subsystem removed from service.
Current Technical Specifications require an operable boron injec-tion flow path in an intermediate or cold shutdown condition.
- 5.
The abnormal operating procedures are ad.equate for responding to loss of the RlIR System.
There is, however, a need for an addition-al improvement to the procedures which will emphasize operator response to loss of the RHR inlet valves.
Since spurious actuation of the valve pressure interlock has occurred in the past, identifi-cation of specific actions required in response to this event will aid the operator in recovering the system.as rapidly as possible.
6a.
As a temporary measure, a Standing Order will be issued to imple-ment the Second paragraph of Item 4.
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e Attachment Page 3 6b.
Additionally, the same Standing Order will indicate the operator action in the event the RHR inlet pressure interlock is spuriously actuated.
7a.
Necessary changes to RHR operating and abnormal_ operating proce-dures will be made by July 30, 1980.
7b.
Changes required by this Bulletin along with North Anna's and Surry 1 s fundamentally different R..1IR design from that of Davis-Besse, will adequately safeguard the core from loss of residual heat remov-al capability.
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I COMMONWEALTH OF VIRGINIA CITY OF RICHMOND
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Before me, a Notary Public, in and for the City and Commonwealth aforesaid, today personally appeared B.
R.
Sy 1 via, who being duly sworn, made oath and said (1) that he is Manager-Nuclear Operations and Maintenance, of the Virginia Electric and Power Company, (2) that he is duly authorized to execute and file the foregoing response in behalf of that Company, and (3) that the statements in the response are true to tqe best of his knowledge and belief.
Given under my hand and notarial seal this JI -th day of Jvne Jq~R.
My Commission expires
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Notary Public (SEAL)
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