ML19225D048

Responds to IE Bulletin 79-12 Re short-period Scrams. Short-period Scrams Are of Operational Concern Due to Lost Availability,But Have Minimal Safety Significance

ML19225D048
Person / Time
Site:	Brunswick
Issue date:	07/24/1979
From:	Utley E CAROLINA POWER & LIGHT CO.
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
NUDOCS 7908060006
Download: ML19225D048 (5)

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[O Mr!.Tnmen P. O'Reilly, Director i

U.l S. Nuclear Regulatory Cornission D

i Region 11 10l Marietta Street, suite 3100 At lanta, Georgia 30303 c.n DRUNS'41CK STEAM ELECTRIC PLANT, UNIT NOS.1 & 2 g

LICENSE NOS. DPR-71 AND DFR-62 DOCKET NOS. 50-325 AND 50-324

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RESPONSE TO lE BULLETIN 79-12 i

5 Tw or Mr. O'Reilly:

31, 1979, tranemitting IE Bulletin 79-12, a

In; response to your letter of May i

Company subraits the following response t Cafolina Power & Light have ccmpleted a prelitzinary review and evaluation of f actors relevant We I

period scrams and have formulated a pregram vs feel will apprcpri-to' short atvly nnd adequatriy address this problem.

period scrams can be Rencrolly clannif f ed nuh cvaluation indicates that short into tun typen, nnmely, high not ch wor th mit uat toma unus11y encountered on t

lity atirture near peak xenon and rod withdrawal beyond the point of critica

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reactivity input can cause a scram from tbr in!"notchoverride." The resultant I

inatrumentnrion.

in ermedinra r n n r.a this type of occurrence is of operational concern due We have concluded that This con-to lost availability although it has minimal safety significance.

lessan our intention to resolve this concern.

clt sten does not position preliminary ntudien for performing accurate estfestes critiersi O u r.

this is a complex task and, even if Successful, I

(P P)' calculations indicate that I

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Mr.

James P. O'Reilly co 1d not be implemented in a short time frame.

Due to the complexity of accounting for time varying nodal xenon changes and temperature corrections, uncertainty in the calculation in anticipated to be large enough to have the potential to give the reactor operator a false sense of security with the

ard to anticipated criticality.

This may result in a short period scram re ere none would have occurred if the operetor was anticipating criticality wh any time based on an interpretation of source range level and period instru-at mentation.

Wi h regard to ahort period scrams during high xenon situations, we have Elcetric's recommended reduced notch worth pro-already incorporated General ures into our rod withdrawal sequences and have not experienced problems ced they do not In addition, General Electric has advised un that in this regard.

induced high notch worthe at believe there have been any scrama due to xenon I

plants that have incorporated the reduced notch worth procedures.

have reviewed and evaluated the operability of the " Emergency Rod In" We itch and have come to the following conclusions:

ow The " Emergency In Rod Notch Override" nwitch is a General Electric type 1.

In general, the switch is very rugged and relinhie although SRH owitch.

any design is subject to malfunction when excessive force is applied.

switch stop is a possible mode of malfunction although this 2.

Tne bent preclude the operator's ability to insert rods since in this abould not then goes pant contact due to a bent mode the switch wiper makes contact, mechanical stop.

'!he momentary contact de-energirca the reactor manual Control" switch to perform the control time. enabling the " Rod Novement consequently, the " Emergency In Rod Notch Over-

" Emergency In" func t ion, ride" switch, even with a bent mechnnical stop, does not preclude rapid

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?!rL James P. O'Reilly i 3.f We are satisfied with the ruggedness and reliability of the " Emergency i

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In Notch Override" switch, Also, the "In-Off-Out Notch" switch serves l an a backup to the "Ernergency In Notch Override" awitch, I

I Optrator training and awarenenn appear to be the bent shor t-t erm rnethodo for l

pr$ventton of short period scrama due to notching past criticality.

I Prkor to res tar dng t' nit Non. I and 2 after the mont recent refueMug, a i

fohmal t raining package was formulated and reviewed by licensed personnel.

I Th4 material used as a reference for this package was reactor theory with npocial emphnnin given to nuberitical multiplication, rod worth, and values i

offreactivity for rod groups, xenon, heatup, etc.

Also stressed were the ch$rt tracen obtained through NRC of the short periode experienced at Browns i

Fer ry (dated January 18, 1979) and listch (dated January 7, 1979) Planto.

Thu,n packnge will become a part of the hot license class as well an all i

relraining claccen ncheduled in the future.

Re. ponyf Sumary:

1.

Our intention is to use single notch or bank notch withdrawal for groups ij two through four when criticulity lu anticipated to occur in groups two i

t hrour,b four.

Operating procedures have been revised to provide for bank l notch withdrawal.

Dunk notch withdrawal is a General Electric approved j

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rrr' t hiul of reducing notch worth.

!l L'e are currently continuing our development program for a calculation of l

SI l the critirni rod pattern.

However, we expect it will take six to twelve g

j months to reach the point where the program's accuracy can bu checked l, n r.n i n n t netuni renetor phynten.

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2., Operating procedures have already been revised to inc u e i

i d we have not i

Electric's recommended reduced notch worth procedures an i

such as high xenon.

i experienced problems due to unusual condit ons s and determined

! We have reviewed our control rod withdrawal sequence With 3.

1 control rods.

! that they minimite the notch worths of individus and rod sequence control syotem (RSCS)

' rod worth minimicer (RWM) is litt.le remaining other than banked ponition ren t r a into imponed, there can further reduce notch worths.

withdtowal that for RWM and RSCS, to Technien1 Specifications requirements s.

Due specini rod acqueneca are not approprinte, ituntions that can Alt bough nome general cautions could be innde on s b.

these cautions do not apply in all cases.

in high notch worth, result rod (s) to exhibit the j

For example, one normally expects the first cane in f act, we have :

h.nhent worth.

This in not always the case; i

worth rod in the critical group is the cur rently wher e the highest Such an inaccurate rod in a sixteen-rod group.

fourth from the last tnr operator to believe caution in the procedure could cause the reac in in that group when, the highent worth rodo ebnt he hon withdrnen the princip!cn of rod worth We feel that f

fnet, he hna not done 80.

han in the operating nre better explained in the clannroom rather t well an tho enceptionn, can be l

c3 the general case, i

procedure so that i

discussed.

ide" nuit ch under pro-Opetability of the " Emergency Rod In Notch Overr ffed t. hat the switch 4.

lonned severe use has been reviewed and we are natin lin suf f iciently rugp,ed and reliable, l

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l Ii Mr, Jnmen P. O'Reilly 5.

On-shift training hno already been completed no previously dincunned and the reactor operator training and retraining programs will ernp'tastre

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I the inctorn relevant to prevention of short period scrams.

Again, we 1

feel that training is currently the bent nolution for prevention of nhort period ncrumn.

k If,nor <1c vc i o rrne n t p rog rarn for a eniculated entimated critical pnnitinn in

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cesat ul, we plan to include this in our overall solution to resolve the eu I

obdrt period scram problem.

However, the prob. tem of providing accurate criti-ca h rod position astirmation under time varying nodal xenon and temperature ch4tigr n In t he WR reactor in formidable, b

Wojerunt that this information untiofirn the requirements of IE Bulletin 79-12.

cry truly yours, w

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E. Utley Executive Vice Prenident E

I Power Supply & Customer Services l

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