ML19259D197

Forwards Response to 790823 Request for Addl Info Re IE Bulletins79-06A & 79-06A,Revision 1, Review of Operational Errors & Sys Misalignments During TMI Incident

ML19259D197
Person / Time
Site:	North Anna
Issue date:	10/15/1979
From:	Stallings C VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	Harold Denton Office of Nuclear Reactor Regulation
References
709A, NUDOCS 7910170343
Download: ML19259D197 (6)

Text

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VIHOINIA E LucinIc Axn Pown n Co>t mxy Iticuxoxn,v norw1A smus October 15, 1979 Mr. Harold R. Denton, Director Serial No. 709A Of fice of Nuclear Reactor Regulation P0/RMT:baw Attn: Mr . O. D. Parr, Chief Docket Nos: 50-338 Light Water Reactors Branch No. 3 50-339 2

Division of Project Management License Nos: NPF-4 U. S. Nuclear Regulatory Commission CPPR-78 Washington, D. C. 20555

Dear . Denton:

This _s in response to your letter of August 23, 1979, " Request for Additional Inforcation Regarding IE Eulletin 79-06A and 79-06A, Revision 1". Our response for North Anna Power Station Unit Nos. I and 2 is attached.

Very truly yours, l0 (klj/

C. M. Stall ngs Vice President-Power Supply and Production Operations cc: Mr. James P. 0*Reilly 3 , ,

7910170 .

Additional Information In Response To Bulletins79-06A and 79-06A (Revision 1)

North Anna Power Station, Unit 1 Docket No: 50-338

2. A chart with a saturation curve and a 50 subcooling curve has been placed in the Control Room. Training has been carried out and documented on natural circulation mode of operation. An engineering review has been initiated to detemine a mechanism which will warn the operator that he is losing his margin to saturation and will provide him with the ability to trend this infomation. This is in accordance with the response for Section 2.1.3.b of NUREG-0578.

The following instrumentation is available to the operator for recog-nition of undesirable void fomation and to detemine the success of natural circulation in cooling the core in the event that total forced Reactor Coolant flow has been lost:

Wide Range Reacte- Coolant System Pressure Wide Range RTD - .at legs Wide Range RTD - cold legs Pressurizer Level Pressurizer Pressure Incore Themoccuples High Head Safety Injection Flow Auxiliary Feedwater Flow Emergency Condensate Storage Tank Level Steamline Pressure Steam Generator Narrow Range Level Steam Generator Wide Range Level Source Range NIS We are presently changing our emergency procedure on Loss of Reactor Coolant flow to provide the operator with the indication and actions to be taken to establish and maintain natural circulation in the event that total forced Reactor Coolant Flow has been lost.

Emergency procedures dealing with a LOCA, loss of secondary coolant and deteriorating pressure conditions were changed on May 4,1979 to incorporate mandatory Reactor Coolant Pump operation as per response to IE Bulletin 79-06A and the revision 1 of IE BulleM n 79-06A. These same procedures were changed to incorporate mandatory Reactor Coolant Pump Tripping as per IE Bulletin 79-06C July 26, 1979.

The emergency procedure for Loss of Reactor Coolant Flow will instruct the operator to maintain at least one steam generator level in the narrow range, pressurizer level >50%, primary pressure saturation point at least 50'F greater than the highest wide range loop temperature or core exit temperature. This procedure will instruct the operator on methods to be used in feeding and bleeding steam generators and instruments to be used to verify that natural circulation is working. These instructions are consistent with Westinghouse recommendations.

These instructions that enhance natural circulation will minimize void formation.

Procedures involved will be revised on or about December 1,1979.

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8. Wlve lineups on Safety Related systons are completed after every re fueli ry. Incked valves on Safety Pelated Systons are verified ard documented with respect to their propor position. Safety Relatoi valves that have position inlication in the Control Roan are to be verifial to be in their proper positions c, a shift turnover check list which will be irtplanented in acconlance , ' th NURBG-0578 Sect ion 2.2.1.c.

'Ihe controllirg unit startup procedure already requires valve checkof f lists be empleted.

9. Systans which are designol to transfer potentially radioactive fluids fran containnent are listed below:

A. Reactor Coolant Punp Seal Water Return

1. No high radiation interlocks

2. Receives Contairment Isolation Phase A

3. Tested operable per T.S. 4.6.3.1.2.a B. Reactor Coolant Letdown

1. No high radiation interlocks

2. Receives Contairment Isolation Phase A

3. Tested operable per T.S. 4.6.3.1.2.a C. Primary Drains Transfer Tank Ptrp Discharge

1. No high radiation interlocks

2. Receives Containnent Isolation Phase A

3. Tested operable per T.S. 4.6.3.1.2.a D. Contairment Smp Pump Discharge

1. No high radiation interlocks

2. Receives Contairment Isolation Phase A

3. Tested operable per T.S. 4.6.3.1.2.a E. Steam Generator Blomlown

1. No high radiation interlocks

2. Receives Contairment Isolation Phase A arri Phase B

3. Tested operable per T.S. 4.6.3.1.2.a arri T.S 4.6.3.1.2.b F. Contairment Particulate ani Gaseous Radiation Monitor Supply

1. No high radiation interlocks

2. Receives Containnent Isolation Phase A

3. Tested operable per T.S. 4.6.3.1.2.a G. Prinnry Vent Header

1. No high radiation interlocks

2. Receives Contairment Isolation Phase A

3. Tested operable per T.S. 4.6.3.1.2.a 3 , 3 H. SI Accmulator Vent l _ . .-

1. No high radiation interlocks

2. Receives Contairment Isolation Phase A

3. Tested operable per T.S. 4.6.3.1.2.a

Page 3 I. Pressurizer Relief Tank Sampic

1. No high radiation interlocks

2. Receives Containment Isolation Phase A

3. Tested operable per T.S. 4.6.3.1.2.a J. Pressurizer Liquid Space and Vapor Space Samples

1. Has high radiation interlocks

2. Receives Containment Isolation Phase A

3. Tested ope-able per T.S. 4.6.3.1.2.a K. Primary Coolant Hot Leg and Cold Leg Samples

1. No high radiation interlocks

2. Receives Containment Isolation Phase A

& Tested operable per T.S. 4.6.3.1.2.a L. Containment Leakage Monitoring Lines

1. No high radiation interlocks

2. Receives Containment Isolation Phase A

3. Tested operable per T.S. 4.6.3.1.2.a M. Containment Vacuum Pump Line

1. High radiation interlocks exist

2. Receives Containment Isolation Phase A

3. Tested operable per T.S. 4.6.3.1.2.a (C.I. Phase A) and E.T.S. 2.2.4.d (high radiation)

N. Residual Heat Removal Sample

1. No high radiation interlocks

2. Receives Containment Isolation Phase A

3. Tested operable per T.S. 4.6.3.1.2.a

0. S. I. Accumulator Test Lines

1. No high radiation interlocks

2. Receives Containment Isolation Phase A

3. Tested operable per T.S. 4.6.3.1.2.a P. Steam Generator Surface Sample

1. No high radiation interlocks

2. Receives Containment Isolation Phase A

3. Tested operable par T.S. 4.6.3.1.2.a Q. Main Steam Drains

1. No high radiation interlocks

2. Receives Containment Isolation Phase A

3. Tested operable per T.S. 4.6.3.1.2.a R. Component Cooling Water from Components in Containment

1. No high radiation interlocks

2. Receives Containment Isolation Phase B

3. Tested operable per T.S. 4.6.3.1.2.b. , ,

Page 4 S. Containment Purge and Exhaust

1. High radiation interlocks exist

2. No Containment Isolation signal

3. Tested operable per T.S. 4.6.3.1.2.c.

NOTE: North Anna is a sub-atmospheric containment design; therefore, the purge and exhaust lines are isolated in T.S. Modes 1, 2, 3, and 4. Radiation interlocks are provided primarily for mitigation of fuel handling accidents in containment.

The following systems have manual valves under administrative control for containment isolation and could carry radioactive fluid from containment:

RER to RWST Post-Accident Hydrogen Recombiner Primary Vent Pot Centainment Air Ejector Suction The following systems have remote manual valves for containmer.t isolation and could carry radioactive fluid from containment:

Recirc Spray Pump Suction Low Head SI Pump Suction Service Water from Recirc Spray Heat Exchangers Containment Air Ejector Suction RHR Sample Lines Note that the above manual and remote manual valves do not have any interlocks for radiation monitoring and containment isolation. The manual valves are normally shut and non-essential remote manual valves are normally shut. Remote manual valves needed for ESF functions would be open in the event of ESF system operation.

10. Techr.ical Specifications dictate the surveillance requirements that must be completed to prove the operability of a safety related system. Technical Specifications requirements are met by periodic tests and logs. Maintenance operating procedures will remove a subsystem / equipment from service for pre-ventative or corrective maintenance. When a subsystem is removed from service or fails, it is entered in an Action Statement log to ensure that the require-ments of Technical Specifications are met. After maintenance is complete, the controlling procedure insures that operability is determined by testing.

Maintenance operating procedures will test the redundant subsystem / train before removal of a portion of the other subsystem / train if it does not isolate it from performing its safety function while testing.

For subsystems that are made inoperable for testing, the redundant train of the system to be removed from service is verified not to be in an Action Statement, has passed its last scheduled periodic test, is visually inspected, and its power supply is operable and not in action statement. These steps are taken and signed off in the maintenance operating procedure before the system is removed from service.

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Page 5 Operability of a redundant emergency diesel is tested by the maintenance operation procedure in accordance with Technical Specifications. The proce-dures will verify that safety related systems powered from the redundant diesel are operable by review of the Action Statement Log.

A detailed review of Periodic Tests will be conducted and completed by 11-1-79. This review is intended to cover system operability detertaination when returned to service following testing. This review will also identify equipment which will be made inoperable for testing purposes.

Transferring of information about the status of safety related systems at shift change will be in accordance with the response to NUREG-0578, section 2.2.1.c.

11. A bakelite sign has been placed within view of the Shift Supervisor's desk stating the reporting requirements to the NRC for IEB 79-06A. The appro-priate Administrative procedure was changed to reflect the reporting require-ments of IES79-05A cn 4/30/79.

12. Hydrogen can be purged from the Primary Coolant System by the following methods (by existing procedures):

A. Volume Control tank operation lowers the hydrogen concentration of the letdown before it is charged back into the primary system by purging the Volume Control tank and maintaining a low gas space pressure.

B. Sampling system allows purging hydrogen gas from the pressurizer vapor space to the Volume Control Tank or directly to the gas stripper.

C. Sampling system allows purging hydrogen gas from the pressurizer relief tank to the Volume Control Tank or to the gas stripper.

D. Degassing the primary system utilizes the gas stripper.

E. Degassing the primary system utilizes the gas stripper while simultaneously purging the VCT gas space with nitrogen.

F. Annunciator Response Procedure provides direction to Pressurizer Relief tank high pressure. Reduces pressure in the pressurizer relief tank by ventin, it to the gas stripper.

G. Unit Shutdown procedure cycles power operated relief valves to vent the pressurizer to the pressurizer relief tank.

H. Gaseous Waste Disposal procedure provides the operating instruc-tions to reduce Hydrogen gas in the gas stripper overhead gas surge tank by the use of the Catalytic Recombiner.

13. One change to the Technical Specifications is required to implement two of the three low-low Pressurizer Pressure Safety Injection actuation. This request will be submitted by 12-31-79, for Unit 1. It is anticipated that the Unit 2 T.S. will be issued with the two of three low-low pressure Pressurizer Pressure actuation as an LCO.

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