ML20084Q733

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AO 50-249/75-24:on 750426,during Routine Calibr of HPCI Area Temp Sensors,Setpoints on 12 of 16 Temp Sensors Found Above Tech Spec Limit.Caused by Unsuitable Existing Temp Sensors for First Operation Surveillance Type Operation
ML20084Q733
Person / Time
Site: Dresden Constellation icon.png
Issue date: 05/06/1975
From: Stephenson B
COMMONWEALTH EDISON CO.
To: James Keppler
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML20084Q736 List:
References
284-75, AO-50-249-75-24, LER-75-24, NUDOCS 8306130554
Download: ML20084Q733 (2)


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. i M - Commonwealth Edison

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. hC Addtr'as',chy to: Post Olf:ce Box 767

?:/ Crocago, litinoi: 60690 BBS Ltr. #284-75 Dresden Nucicar Power Station. a R. R. #1 ,

I Morrio, Illinoin 60450  !

May 6, 1975 M41 h b

  1. /

.Mr. Jarr.es G. Koppler, Regional Director J~

Directorate'of Regulatory Operations-Region III U. S. Nuclear Regulatory Cornission ,

s 799 Roosevelt. Road y

. Glen Ellyn, 1111noia 60137 'Qf}W\\'

SUDJECT: REFORT OF l.E!OR'.'A OCCIT.BE!CE PER SETION 6.6. A OP ' DIE TFCINICl4 SPECI-'ICATIC::S

  • HIGH P3ES5URE CCOLMP II'JECTION SYSTE1/JtEA TE:PF3/.TURE SUITCH S~r7. Por ? '!JCL'.TICII

References:

1) Regulatory Guide 1.16 Rev. 1 Appendix A
2) Notification of Region III of U. S. Nuclear Regulatory Cocmiccion

~~

Tclophone: R. Knop, 1.pril 28, 1975 at.1600 hourn T01 err.? J. Perpleri ^r'91 94, 1975 a.t 5646 b~~r Report Number: 50-249/1975-24

, Report Date: Fay 6, 1975-

\

Occurrence Date: April 26, 1975 Facility: Dresden Nuclear Pcwcr Station, Morris, Illinois IDEh'PIFICATION 0? CCCURR71:CE ..

_T_uelve of the hich crecsure coolar.t_injheystem (HFCI) arca temperature sencora 2370A-D, 2371A-D, 2372A-D, and 2373A-D were found with actpointa above the, 6200*P technical specification limit.

CONDITIONS PRIOR TO CCCURRD!CE Dresden Unit 3 was in the refuel modo with a refueling outage in progrecs.

DESCRIPTICM OF GCCURRE CE During the routine ocheduled calibration of the HPCI arca . temperature censors,

= the actpint;c. on twelve _of thc cixcaen te:perature censcrs were fcund to bc

.abovo the 200*P li.e.it. The reactor was in the reilici raode with the head rcmoved, .

therefore no im.cdiate corrective action uas necoscary. -

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B306130554 750506 . @/ '/^

sPDR ADDCK 05000249:

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  • o PDR:

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Mr. James G. Koppler - ,- ' '

hay 6,1975 DESIGNATION OF APF/REh'P CAUSE OF OCCITriRENCE (Design Error)

  • The existing temperature sensors are not suited for a "first operation" surveillance type operation.

-ANALYSIS OF OCCURRCCE The -function .of the temperature censors is to isolate the HICI turbine steam supply in the event of a sto:m leak in the EPCI cubicle. The technical specifications require an isolation at or below 200*P. The "as found" sotpoints of the 16 switches involved would have provided an isolation at 202' F minimum and 249* P m: i.mun. The saturation temperature corresponding to.the mini.u:m design inlet pressure would be 360* P. It is therefore -

L Jconcluded that there would be sufficient differential temperature to '

activate the closure signal even with the inst"uments'out of tolerence.

In addition to the high temperature sensors, steam line break detection is also

.provided by differential pressure sensors. Those devices are checked monthly.

'It is thereforo concluded that no significant safety, hazard was created as a result of the high setpoint of the HPCI temperature sensors.

_ CORRECTIVE ACTION

'To prevent future occurrence, a plant rnodification (M12-3-74-143) will be made.

The modification vill-install a liquid filled tcmperature sensor which is better suited for trat trip operation than those presently installed.

FAILURE DATA Thesc' switches have been found with high notpoints many times and the j subsequent investigation has detemined that the existing switches are yd misapplied in"that an accurato first operation trip point cannot be

. consistently obtained.

The manufacturer of the_ switches (Pcnuall Inc) has investigated the problem Land has stated that the existing switches are not properly cuited uhon a Arctitrip setpoint is required. The switches involved Ere Ibnwal series .

1700 hermetically sealed thermomritch type units. ,

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v W YB. B. Stephenson.

, Superintendent ,

E .BDS: cmp '

' l Pilc/NRC, '

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