ML20090E161

AO 50-220/74-16:on 741210,intermediate Range Monitor 12 Found Inoperable.Cause Apparently Due to Defect in Cable or Detection.Repair Will Be Conducted on Sys

ML20090E161
Person / Time
Site:	Nine Mile Point
Issue date:	12/19/1974
From:	Schneider R NIAGARA MOHAWK POWER CORP.
To:	Goller K Office of Nuclear Reactor Regulation
References
12926, AO-50-220-74-16, NUDOCS 8303110589
Download: ML20090E161 (7)

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. O l NIAGARA MOHAWK POWER COPPORATION.

FJIAGARA .-t MOHAWK l 300 ErtlE COULEV AFID. WLtiT

• SYtt ACUSE. ii. Y.13 202 December 19, 1974

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50-220 Rect?vgg e lit. Kari R. Gotter -2 DEC 23 ISIA 2 Assis. tant Dinector of ,0peAa. ting Reactors Q "kaj up  :

N Dihectorate of Lxccas.usg s,4 United States Atcmic Energij Cosr. mission (*e

• Sutkq Washington, D.C. 20515 m .,

Ocar Itt. Gotter:

In accordance tolth .the Teclutical Specifications for the N.ine !.fiic Point !!ucleat Station, Unit til, the enclosed Abnormat Ocetoutance Report (14-16) is being submitted.

This is in .the accepted for=t a!. detai.Ced in Regulatony I".' f{.

Guide 1.16, Rev. 1.

Ver(: thuit) tjourb, Original signed by R.R. Schneider R.R. Schneider Vice Presidentt Electric Cperations -

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O-NIAGARA MOHAWK POWER CORPORATION NI AGARA ', MOHAWK DATE: December 16, 1974 ,

SUBJECT:

Abnonnal Occurrence Report No. 50-220 /74-16'  ;

The-enclosed Abnormal Occurrance Report is being submitted in accordance with Technical Specifications-Section 6.

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TO: James P. 0?Reilly '

Directorate of Regulatcry Operations Region'1' 631 Park Avenue King of Prussia, Pennsylvahia 19406 FROM: Niagara Mohawk Power Corporation Nine Mile Point - James A. FitzPatrick Site P.0, Rnv #32 Lycoming, New York 13093 t

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Docket 50-220 f

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NlAGARA MOHAWK POWER CORPORATION NtAGAHA MOHAWK

SUBJECT:

Abnormal' Occurrence 10 Day Letter ,

REFERENCE:

Licenso DPR 17 .

i Report No.: 50-220 /74-16 .

l Report Date: 12/10/74 .

Occurrence Date: 12/10/74 Facility: NY NMP #1 l .

Identification of Occurrence:

One inoperable IRM (12), in Safety System 11 l Conditions Prior to l

Occurrence: Steady State Power Routine Shutdown-llot Standby Cold Shutdown Load Changes Refueling Shutdown 3 X Routine Startup other Description of f.he Occurrence:

During routine surveillance it was found that IRM (12) was -

inoperabic. Technical Specifications Tabic 3.6.2a requires -3 operabic Instrument Channels per trip. system. This LCO-was satisfied as the other 3 IRM's in safety system 11 were operable.

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Apparent Cause of the Occurrence:

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Design ,Procedurc Manufacture Unusual Service Installation /Const. Condition Operator X Component Failurc Other (Specify)

Cable or detector failurc Analysis of Occurrence:

The IM1 system is used to detect and indicate neutron flux 1cvel between the source range and the power range instrum-entation. Trip signals are provided to the RPS in a one out of two r.wice logic. It is possibic to bypass an inoperative IIG! channel from the RPS. The switches for this function are arranged so that only one channcI in a safety system bus ca_n be bypassed at one time. The number and locations of the IIBl detectors have been analytically and experimentally determined to provide sufficient intermediate range flux levn1 information'under the worst permitted bypass or detector failure conditions. A range of rod withdrawal accidents has been analyzed. In the most severe case the reactor is just sub-critical with one fourth of the control rods plus one more rod removed in the normal operating sequence.

The error is the removal of the control rod adjacent-to-the-last rod withdrawn. This 16 cation is chosen to maximize the-distance to the second nearest detector for cach RPS trip system. The nearest detector in cach trip system:is usumed to be bypassed. The rod withdrawal is '.'seen" and a trip. initiated, y n,q

.s Therefore, it can be concluded that one IRM being inoperable would not have prevented the performance of the intended safety function of the IRM system. Further, no hazard would have.

been presented to the plant safety or health and welfare 'of the general public from this event.

Corrective Action: ,

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- The failure is apparently in either the-cable or the. detect'or ~

itself. Therefore, a power reduction and de-inertion of the drywell would be required to repair the IRM. This repair will be under-taken during a refueling shutdown and the nature of repair included in the annual report.

Conclusion:

1The 1141 will remain bypassed or in a trippe'd condition-until-repairs can be made. The LCO Table 3.6.2a is satisfied. There-fore,,it is concluded that no hazard is presented to the general public. ,

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l,..l* NIAGARA MOHAWM POWEN Cordf' ORATION

inAo^ter aQ monnu DNIII

Deceber 10, 1974

SUBJECT:

Abnormal Occun ence Repet No. 50-220 r74-16 The enc.losed prc)ir.tinary AOR is being submittet. in accordance with Technical Specifications 'Section 6.

'fo: Jasaes P. O'Reilly -

Directorate of Regulutory Operations .. f ~

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j' l, King of Prussin, Pennsylvania, 1940f> Q f.

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Ninnarn Mohawk Power Corporation [,M. A ,

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P,0.. Box.#32 djj y\Lyy/ 83 Lyconing,.Now York 150D3 l Dockot 50 220 s

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14fAGARA MOHAWK POWER COFTPORATION

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SDDJ ECT:._ Abnornal Occurrence 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> Notification Confirming ffr. T..Perkins phone conversation With __Mr'. Y. She.ilonky .

AEC RO:1 office on '

17f10/74 .

REFJ3RTECB: License DPR 17 _.

Rrport No : 50 220 /74-16 Rsport Date: 12/I_0/74

• Occurrence Dato: 12/10/74 - -

Puoility: IN TC'#. # 1 2 -

Identification of" Occurrence:

One inoperablo IRM (12), in Safety System :1 ,

Conditions Prior to Ocettrrenco: Steady Stute Power- Routino Shutdown llot Standby ,

Cold Simtdown Load Change.*

Rofuoling Shutdown x Routine Sturtup _ Other Ducription. of the Docurrence:

During routino aurve511once it uns found that IR4 (12) was inoperable. Technical Specifications Table 3.6.2a requirer -3 operabic Inntrtnwnt channels per trip systera. This LCO wp untinfled as the othor 3 IRM's in safety system 11 were operable. ,

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Design -

Procedure

" Maufacture i . Unusual Service ,

Inst all ation/Const . Condition

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Cable or detector failure. ,

Analysis of Occurrences b IRM Syster: is used to detect and indicate neutron flux level' botuoca the source ranne and the power range .instruzz-entation. Trip signaln are provided to the HPS in a one out of tuo tuice logic. It is por.sible to bypass an inoperativt.-

IPJS chttuni fro:n the RP3. Tho switches for this function ure-prec.t':cd'.sc tbar only our chunnel in a sat *ety system bus cun be bypnosed'at one tine. The rnnbur and'. Iocations of the 11tn detectora Irm been unalytically ani experiuant.nlly dhterrained to provido sui'ficient in:crraediate range flur.IcVet infornntion under the worct permitted bypnos or deteetor failuro conditions, A ronce of red uithdr teni occidents hno been unnly:ud. In the most .'wveir cace th:r rc=ctor in ju::.t sub-critical with. ons+ 1'ourth of the control roda plus ona corn rod recoved in tho normni operatin;; sequence.

Tha cerez- is the remval of the cent.rol rod adjacent to the inst rod withdruyn. This location is chosen to noxioite ttne

. diatsuco to tho ..ecoral nenrost dotee. tor for cash IWS trip cyt.t c.v . The ncatest detector in. cach trip sy.vten in umraed -

to be bypsused. 'lhe rod' withdraual is "scen" and a trip initiated.

Therefore>. it can be concluded that one IRM bein; inoperablu Hould not have preventexi the part' ore.2nco of the intended safety function of thu IlUI systen. Further.. no hazard.vould have bcon. presented to tha plant safety or hvalth and welfore, of the general public from this ovcnt..

Corrective /iction Luter-Failtire Datu:  : ,-

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