ML19220B210
| ML19220B210 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 04/11/1977 |
| From: | Arnold R Metropolitan Edison Co |
| To: | O'Reilly J NRC Office of Inspection & Enforcement (IE Region II) |
| Shared Package | |
| ML19220B202 | List: |
| References | |
| GQL-0475, GQL-475, NUDOCS 7904250511 | |
| Download: ML19220B210 (2) | |
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METROPOLITAN EDISON COMPANY surr:=uncr acawusucunune::cu
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OST OFFICE SCX 542 REAOtNG,PENNSYLVANI A 196:3 TELEPHCNE 215 - 3:9-0C01
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.-- -,-:si CQL CLT5 Mr. J. ?. O'Reilly, Director U.S. Nuclear Regulatory Cc==1ssic Office of Inspection & Inforce ent Regien 1 631 ? ark Avenue 7d.ng of Prussia, ?e==sylvania 19406
Dear Sir:
~hree Mile Island Nuclear Station Cait 2 (~XI-2)
License No. C??R-66 Docke No. 50-320 Vital ?cwer Supply Inverters C March 10, 1977, Mr. Eaines of your office was verbally notified of a si:uatics which Metropolitan Edi;o Cc pany considered to be reportable in accordance with the require ents of 10CFR50.55(e).
day follow-up letter.
his letter cc stitutes the required thirty-Descric~.te:
'inile conducting tests c the vital pcuer supply inverters, two deviatices frc=
the engineer's specifica:1c require =e::s were ice::1fied.
~he inverters are the preferred power scurce for the static svi:ches with the regulated trans-for:ers as their backup.
3c h are designed to supply 120 volt pcver to the static switches. Tne specifica:ic required the pcuer to the static switches to transfer to the regula:ed transfor=ers when voltage en the inverters d: cps by 3.
FieH esting of the inverters shewed ba: the transfer did not occur in sc=e instances until the voltage dropped to 38 volts.
This was due to the vender, Solid State Centrols, Inc., not supplying a required ce=penent with the inverters, which vculd effect this transfer at the required voltage peduction.
Additic ally, anc:her specificatica require ent was that after transfer frc: the inverter to the regulated transfer =er, pcuer uns no: to transfer back to the inverter until the inverter had stabilized for 2 to 10 secceds.
Ccatrary ::
this require ent, the vendor supplied eouip=ent which prchibits transfer baci to the inverter unless the inverter stabilizes within 2 to 10 secceds of the 1:1:dal transfer.
i 74 'C21 790h5 061L,
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J. P. O'Reilly ^P r,,, -,, - i i-s
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sp Analvsis cf Safety I elicati m
~he deficient circuits identified affect cely the con:rol of the static switches in respcese to an inver:c: failure and do not affect the nor=al operatic: ef the vital pcwer supplies or their abili:7 to supply 1207AC pcwer to safety related 1 cads under no m i cceditions,
~he four vital pcuer supplies are indepcedent and redundant and supply independent and redundant
- 'hile the probability of lesing a single vital power source safety syste=s.
a in respecse to a failure of a single static inverter is sc=ewhat greater vith the equipment as supplied, the loss of a single vi:al pcwer scurce will not affect the redundant scurces or prevent safe shutdew: cf the plant using redundan: safety syste=s.
For this reases there veuld be no effect c health or safety of the public or plant staff.
Corrective Actic:
~te vendor was i=ediately ec : acted regarding these discrepancies.
Dis-cussiens between the Architect Engineer and the vendor have revealed that with d---
cdificaricas, the equip =e : can be upgraded to =eet specifica ic:
requirements.
O.e engineering for these sedificacices is in progress, and all sedifica:1cas will be cc=pleted by fuel loading.
Infor=ation and docu-
=entatic: asscciated with these ecdificatices vill be available at the site for your inspectice.
7ery truly ycurs, f
N L,d o
v E. C. Ar/nold Vice Preside :
cc: Dr. Ir:s: Volgenau, Director Office of '_:spectics & Inforcence:
U.S. Nuclear Regulatory Cc issio:
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