ML20033C121
| ML20033C121 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 11/24/1981 |
| From: | Crouse R TOLEDO EDISON CO. |
| To: | Stolz J Office of Nuclear Reactor Regulation |
| References | |
| 751, NUDOCS 8112020686 | |
| Download: ML20033C121 (3) | |
Text
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%m= EDISON Ao4Ano P. CROUSE vu prwoent Docket No. 50-346 N"*"
141912M-5221 License No. NPF-3 Serial No. 751 Ju
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November 24, 1981 Director of Nuclear Reactor Regulation Attention:
Mr. John F. Stolz, Chief DE01 1984 9 Operating Reactors Branch No. 4
" QMuT" D Division of Operating Reactors United States Nuclear Regulatory Commission
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Dear Mr. Stolz:
On July 23, 1980 (Serial No. 635) Toledo Edison responded to your letter of June 24, 1980 concerning bypass and reset capability of the Engineered Safety Features (ESF) equipment for the Davis-Besse Nuclear Power Station, Unit 1.
Subsequently, representatives of your staff came to Toledo (November 17-19, 1981) to review in detail the design of the ESF equipment.
On November 23, 1981 our NRC Project Manager contacted us with several issues arising from the review that were to be resolved prior to restart of the unit which is currently in a condenser repair outage. The three items of concern are listed below with Toledo Edison's responses.
Item 1 Blocking of Safety Features Actuation System (SFAS) signals to the contain-ment purge and exhaust isolation valves (CV5005, CV5006, CV5007 and CV5008) should not be permitted, by design, in Operating Modes 1, 2 and 3.
Response
Although the system design has the capability of providing such a block signal to these valves, the operator is specifically instructed by both procedure and training on specific plant conditions that must exist to allow blocking of a few selected SFAS requirements.
In the case of the containment purge valves the operators are currently prohibited from opening these valves during the presence of SFAS signals under any plant conditions. Toledo Edison believes these administrative controls are adequate for assuring that' the containment purge valves remain closed in all SFAS initiation conditions.
Your staff, however, indicated that this approach was unacceptable because the system design permits inadvertent blocking of the ESF actuation signal THE TOLEDO EDISON COMPANY EDISON PLAZA 300 MADISON AVENUE TOLEDO OHIO 43652 0112O20686 811124 I
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. to these valves. As a result, Toledo Edison will provide by physical restraint or system design alteration, a SFAS block inhibit feature on the containment purge valves (CV5005, CV5006, CV5007 and CV 5008). Detailed design of this is not completed and will be forwarded to you for informa-tion when available. Until a block inhibit feature is provided, Toledo Edison will continue its commitment not to open these valves in Operating Modes 1, 2 and 3.
Item 2 Adequate guidance and training should be provided to the control room operators to indicate the proper action required to manually reinitiate a safety features actuation during the presence of an equipment block.
Response
A Special Order has been issued by the Station Superintendent to all station personnel. Knowledge of this condition will be verified of all licensed personnel prior to their assuming shift duties in Modes 1, 2 and 3.
Similar instructions are being mounted on the control board prior to Mode 3 entry.
Item 3 Following the blocking of a SFAS trip or any SFAS output module, a single operation of the manual actuation swi:ch in the control room should be capable of reinitiating an automatic system protective action without a second operator action.
Response
Toledo Edison feels that the actions taken in response to Item 2, the current procedures and the inherent design feature prohibiting pre-actu-ation blocking are adequate to insure safe operation. We will, however, proceed with a design modification for the first refueling outage follow-ing January 1,1983 that would reduce the two adjacent button operator action to a single button operation. This will specifically be addressed in the DB-1 control room human factors review.
If the results of this review show this to be an unnecessary change, those results will be forwarded as justification of the current design.
Very truly yours, 19 kW RPC:RFP jh c/8 attachment cc:
DB-1 Resident Inspector a
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a Docket No. 50-346 License No. NPF-3 Serial No. 751 November 24, 1981 Attachment SPECIAL ORDER Previous procedure revisions have addressed generic precautions as well as specific rules for blocking and overriding SFAS signals to various equipment actuated by the SFAS. Specific guidance for the operator on how to remove the block or how to reactuate blocked and overriden components was not included in the precautions. The below information will serve to reinforce previous precautions as well as provide guidance on reactuation after the blocking of SFAS components:
IF ANY SFAS SIGNAL TO SOME ESF EQUIPMENT IS " BLOCKED" (I.E.
OVERRIDDEN), THAT EQUIPMENT IS INCAPABLE OF RESPONDING TO EITHER ANY i
SUBSEQUENT AUTOMTAIC ACTUATION SIGNAL OR THE SYSTEM-LEVEL MANUAL ACTUATE (" TRIP") PUSHBOTTONS.
BEFORE AN OPERATOR " BLOCKS" ANY SFAS SIGNAL, E MUST ASSURE THAT THE SAFETY FUNCTION OF THAT EQUIPMENT IS NO LONGER NEEDED. AFTERWARD THE OPERATOR IS TOTALLY RESPONSIBLE FOR THE PROPER OPERATION OF THAT EQUIPMENT, INCLUDING REACTUATION IF REQUIRED, UNTIL THE " BLOCK" IS REMOVED.
REACTUATION, SUBSEQUENT TO A " BLOCK", CAN BE ACCOMPLISHED TWO WAYS.
FIRST, AT THE EQUIPMENT LEVEL, " BLOCKED" EQUIPMENT WILL RESPOND TO THE INDIVIDUAL CONTRCL SWITCHES FOR THAT PIECE OF EQUIPMENT.
SECOND, AT THE SYSTEM LEVEL, OPERATION OF THE SYSTEM-LEVEL " RESET" PUSHBOTTON WILL CLEAR ANY OUTPUT LOGIC BLOCKS IN THE SYSTEM (OUTPUT LOGIC " BLOCKS" ARE THE BLOCK SWITCHES NEXT TO THE SAM LIGHTS AND ON THE OUTPUT MODULES). THE EQUPIMENT WILL THEN RESPOND TO THE SYSTEM-LEVEL MANUAL ACTUATE (" TRIP") PUSHBUTTON AND TO AUTOMATIC ACTUATION SIGNALS.
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