ML20003E646
| ML20003E646 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 04/02/1981 |
| From: | Gallagher J PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| To: | Eisenhut D Office of Nuclear Reactor Regulation |
| References | |
| RTR-NUREG-0737, RTR-NUREG-737, TASK-2.K.3.03, TASK-2.K.3.16, TASK-2.K.3.18, TASK-3.D.3.4, TASK-TM NUDOCS 8104070488 | |
| Download: ML20003E646 (6) | |
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O PHILADELPHIA ELECTRIC COMPANY-i u.
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April 2, 19 1 Re: Docket 'los. CO-?77 50-??4 Mr. Darrell G.
Eisenhut, Director Division of Licensing US '!uclear Regulatory Commission Washington, DC 20555
SUBJECT:
In fo rm ation Requested by ?!UREG 0737,
" Clarification of TMI Action Plan Requirem.ents" 2 ear Mr. Eisenhut:
Several of the TMI related requirements identified in ?!UREG 0737 request the licensee to submit proposed modifications and the res*
of engineering studies ev aluatin7, new design standa A response to the following ?!UREG 0737 tar,ks is presenc-. in the attachments.
The number in parenthesis corresponds with the TMI Action Plan identification numbers.
Attachment A-Reduction of Challenges and Failures of Relief Valves - Feasibility Study and System Modification (II.K.7.16)
At t a chm ent B-Modification of Automatic Depressurization System Logic - Feasibility For Increased Diversity for Some Event Sequences. (II.K.?.19)
Attachment C-Control Room Habitability Requirements (III.D. 7. u)
We believe these enclosures provide the information requested by the fl R C.
Should you have any questions regardi% this submittal, please do not hesitate to contact us.
Very trul y yours,
b 44,/m S \\
Enclosure
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6 PEACH BOTTOM ATCMIC PC'4ER STATI0t!
ATTACHMENT A NUREG 0717 Requirement:
Reduction of Challenges and Failures of Relief Valves An investigation of the feasibility of reducing challenges to the relief valves should be conducted.
Changes should be im plem ent ed to reduce challenges by an order of magnitude.
The changes shall be accomplished during the next scheduled refueling outage following staff approval or no later than i-one year following staf f approval.
Response
Philadelphia Electric Company participated in the General Electric BWR Owners' Group evaluation of this NRC requirement.
The Owners Group's evaluation report was submitted to the MRC with a cover letter dated March 31, 1991, D. 9. Waters, Chairman, BWR Owners' Group to D. G.
Ei s enhut, P!R C.
We generally concur with the Owners Group's position on this task as provided in the referenced report.
The report concludes that adequate core cooling. is maintained following a Stuck Open Relier Valve (SORV) event under degraded conditions.. Therefore, the reduction of the frequency of SORV events is not of great cor.cern for a BWR.
The report identifies a. number of candidate modifications and their benefit fo r reducing challenges to relizvf valves.
It is left to each licensee to select those modifications that would be approcriate for implementation on their facility.
'la have selected the modifications listed below.
Two of these modifications have already been implementes at Peach Bottom and appropriate credit has therefore been taken.
We propose implementation of the remaining three options in accordance with an appropriate schedule.following notification of NRC staff approval.
Th e number in the parenthesis below refers to the applicable section in the Owners' Group report..
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The proposed modifications are:
1.
Low '4ater Lev el Isolation Setooint (3.1.1.1)
This modification involves lowering the reactor water level isolation setpoint for the MSIVs from level 2 to level 1 thereby potentially reducing the frequency of reactor isolation events.
This modification is already a part of our current commitment to the t'RC to implement AT'.4S Alternate 3A modifications.
Verification of the acceptability of this modification in terms of the ECCS analysis must be complete prior to implementation.
2.
P'/R Emerg ency Procedur e Guidelines (1.1.1.1)
This modification takes credit for the Emergency Procedure guidclines currently being im pl em ent ed at Peach Pottom which instruct the operator to manually open an SRV if they are cycling so that the reactor oressure is maintained below the minimum SRV setpoint.
This limits cycling of the SRVs and thereby reduces the potential for an SORV ev ent.
3.
Rev is ed Relief Valve Setpoints (3.1.3.2)
This modification revises the relier valve setpoints upward to allow additional margin to the relief valve opening setpoint, thereby minimizing the challenges to
.the SRVs.
This modification has already been imnlemented at Peach Bottom.
u.
Analog Tr ansm itt er/ Tr ip Unit System (3.1.3.1)
This modification incorporttes analog transmitters and bistable trip units in place of the direct acting differential pressure, pressure cnd water level switches.
This permits longer intervals between surv eillance tests, therefore reducing the potential for inadvertent scrams due to. valving -errors.
This modification has already been ' implemented at Peach.
Bottom.
5.
Reduced MSIV Testing (3.1.4.4)
This modification reduces the potential for inadvertent
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isolations by reducing the frequency of testing of the "SIVs.
Such a reduction would involve a change in the-
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Technica? Specifications to allow a reduction in the number of closure timing tests of the "SIVs from once per quarter to once per refueling cycle.
Analfsis of Peach Bottom surveillance test 'esults daring the past 2 years indicates that the recommended reduction ir the frequency of full closure tests will not compromise t"e operation of the MSIVs.
During this period there were no instances of a valve failing to close when called upon, and out of 260 individual valve closure timing tests, only three valves failed to meet the 1 to 5 see Technical Specification requirement, closing in approximately 2 seconds in each of the three instances.
This results in a closure timing test pass rate of approx imately 99".
An application for a Operating License Amendment regarding reduced testing frequencies will depend upon the NRC conclusions regarding this matter.
A maximum reduction of approximately eighty percent in the incidence of SORV events can be achieved by the above modifications.
We consider such a reduction to be responsive to the NRC r?quir,rnent.
t It should be.noted that a modification discussed in the Owners' Group Report involves more stringent leakage criteria and early removal of leaking relief valves.
This modification has the potential for reducing SORV events by a significant amount.
However, a commitment to adhere to such a leakage criteria would probably result in unwarranted shutdowns and is therefore not cost effective when compared to the minimal safety impact.
Some credit, however, should be given for the current program at Peach Bottom of monitoring leakage and repairing / replacing leaking valves during planned outages.
This program, combined with the modifications noted above,'should satisfy the NRC requirement fo r en order of magnitude reduction in SORV event frecuencies.
PEACH Dp,TTM ATOMIC PCVER STATTON ATTACFMENT 9 MUREG 0737 Rsquirement Automatic Depressurization Fystem Logic (II.K.3 18)
The automatic depressurization system (ADS) actuation logic should be modified to eliminate the need for manual actuation to assure adequate core cooling.
A Peasibility and risk assessment ttudy is required to determine the optimum approach.
One possible scheme that should be considered is ADS actuation on low recetor-vessel water level provided no high-pressure coolant injection (HPCI) or bish-pressure coolant system (HPCS) flow exists snd a low-pressure emergency core cooliaq (ECC) system is running.
The logic would complement, not replace, the existing ADS actuation logic.
The licensee shall describe the proposed modifications for staff approval by Acril 1,
1982.
Response
Philadelphia Electric Company participated in the General Electric BWR Owners Group's feasibility and reliability assessment study.
The _ study was submitted to the MRC with a cover letter dated March 31, 19?1, D. B. Waters, Chairman, BWR Owners' Group to D.
G.
Eisenhut, NRC.
We concur with the conclusion.of this study.
Five options,. including an assessment of the current design of ADS and the scheme suggested for consideration by the NRC, were et aluqted in the stud y.
The results showed that although the current ' design coupled ' with implementation of.the emergency
. procadure guidelines is satisf actory, an ADS modification will furtner reduce plant risk.
We concur with the evaluation report that certain of the five options are preferred and have selected Option.3 for Pesch Bottom.
Option 3 involves the addition of a bypass of the high 'drywell pressure initiation signal if the reactor water level remains below the low pressure ECCS initiation setpoint for a sustained period.
Detailed implementation will require consideration of broader scope issues, such as the final resolution of the Anticipated Transient Without' Scram issue (which may~ affect the ADS logic).
We are proceeding to do the ' detailed. design work necescary with the intent of describing the proposed modification to the - NRC by April 1, 1992 as required.
Implementation will. subsequently be
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. completed in accordance_with the schedule contained-in NUPEG 0737.
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PEACH BOTTOM ATCMIC PC'4ER STATION ATTACHMENT C MUREG 0737 Reouirement:
Control Room operators shall be adequately protected against the effects of an accidental release of toxic and radioactive gases.
Specific design criteria fo r control room habitability were identified.
Modifications needed for compliance shall be implemented by January 1,
1983.
Response
The results of our control room habitability study were presented in Attachment O of the January 8, 1981 letter, 3.
L.
Daltroff to D. G.
Eisenhut, NRC.
The only potential hazard identified was the on-site storage of chlorine..Our investigation of possible
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modifications concludes that the most effective means of eliminatin6 this hazard involves the replacement of the liquified chlorine gas system with a sodium hypochlorite biocide system.
An engineering effort is underway to install the sodium hypochlorite system with the intent of meeting the schedule completion date of January 1,
1983 i
Presently, self-contained breathing apparatus are available for use by control-room personnel in the event of a smoke, tax gas, or radioactive ' gas hazard.
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