ML19253A624

Notifies Licensee of Interim Actions Required for Plant Operation Pending Final Resolution of Anticipated Transient W/Failure to Scram.Requests Response by 791019

ML19253A624
Person / Time
Site:	LaSalle
Issue date:	08/17/1979
From:	Varga S Office of Nuclear Reactor Regulation
To:	Brian Lee COMMONWEALTH EDISON CO.
References
REF-GTECI-A-09, REF-GTECI-SY, TASK-A-09, TASK-A-9, TASK-OR NUDOCS 7909100590
Download: ML19253A624 (3)

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Docket Nos. 50-373 AUG 171979 and 50-374 Mr. Byron Lee, Jr.

Vice President Conmonwealth Edison Company P. O. Box 767

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Chicago, Illinois 60690

SUBJECT:

INTERIM ACTIONS NEEDED FOR PLANT OPERATION PENDING FINAL PESOLUTION OF ANTICIPATED TRANSIENT WITH FAILURE TO SCRAM (ATWS) - (L A SALLE COUNTY STATION, UNIT NOS.1 & 2)

In December 1978, the Nuclear Regulatory Conmission (NRC) staff issued Volume 3 of HUREG-0460 which describes the proposed type of plant modifications the staff believes are necessary to. reduce the risk from anticipated transients with f'ailure to scram ( AThS) to an acceptable level. The NRC's Regulatory Requirements Review Conmittee completed its review in January 1979, and concurred with the staff's approach described in Volune 3 of NUREG-0460 insof ar as it applies to the La Salle County Station, Unit Nos. 1 & 2.

The staff has issued requests for the industry to supply generic analyses to confirm the ATWS mitigation capability described in Volume 3 of NUREG-0460. Subsequently, the staf f plans to present its recommendations for rulemaking on ATWS to the Conmission. The Conmission would, by rulemaking, detemine the required modifications to resolve ATWS concerns and the required schedule for the implementation of such modifications. The La Salle County Station, Unit Hos.1 & 2 would of course, be subject to the Commission's decision in this matter.

Based on considerations described in pages 42 through 45, Voltrie 3 of NUREG-0460, the staff generally concluded that plants with operating licenses can continue to operate without undue risk to the health and safety of the public during the estimated 2 to 5 year period needed to implement the necessary modifications.

However, in addition to our licensing requirement for a recirculation pump trip to mitigate the short-term consequences of ATWS events, the staf f believes the following steps should be taken as a prudent course prior to the issuance of an sperating license in order to further reduce the risk from ATWS events during the interim period before the required plant modifications as determined by the Cornission are coupleted.

7909100590 A S3CG5s

Mr. Byron Lee, Jr. ggg y 7 Tgl9 1.

Emergency procedures should be developed to train operators to recognize an ATWS event, including consideration of scram indicators, rod position indicators, average power range flux monitors (APRM), reactor vessel level and pressure indicators, relief valve and isolation valve indicators, and containment temperature, pressure and radiation indicators. The procedures should be sufficiently simple and unambiguous to permit prompt operator recognition of an ATWS event.

2.

The operator should be trained to take actions in the event of an ATWS including consideration of manually scraming the reactor by using the manual scram buttons followed by changing the operation mode switch to the shutdown position, stripping the feeder breakers on the reactor protection system power distribution buses, scramming individual control rods from the back of the control room panel, tripping breakers from plant auxiliary power source feeding the reactor protection system, and Valving out and bleeding off instrument air to scram solenoid valves.

These actions must be taken immediately af ter detection of an ATWS event.

The operator should also be trained to promptly place the residual heat removal systm ir the suppression pool cooling mode to reduce the severity of the containment conditions; and actuate the standby liquid control system if a scram cannot be made to occur.

Early operator action as described above, in conjunction with a recirculation pump t rip, would provide significant protection for some ATWS events, namely those which occur (1) as a result of common mode failure in the electrical portion of the scram system and some portions of the drive system, and (2) at low power levels where the existing standby liquid control system capability is sufficient to limit the pool tempe ature rise to an acceptable level.

We will require that you submit your procedures for our review by October 19, 1979.

Our review will include a visit to your plant to determine the feasibility of implementing your proposed procedures through operator simulation of the steps. Our evaluation must conclude that acceptable procedures and operator training are in place prior to the issuance of an operating license for the La Salle County Station, Unit Nos.1 & 2.

% erely, p h-b St even Varga, Ac i g Assistant Director for Light iter Reactors Division of Project Management cc : See next page

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s Mr. Byron Lee, Jr..

AUG 171979 cc : Richord E. Povell, Esq.

Ishma, Lincoln & Beale One First National Plaza 2400

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Chicago, Illitiois 60670 Dean liansell, Esq.

Assistant Attorney General State of Illinois 188 West Randolph Street Suite 231o Chicago, Illinois 60601 Mr. Roger Walker, Resident Inspector U. S. Nuclear Regulatory Connission P. O. Box 737 Streator, Illinois 61364 1

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