ML17252A280
| ML17252A280 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 03/09/1977 |
| From: | Stephenson B Commonwealth Edison Co |
| To: | James Keppler NRC/RGN-III |
| References | |
| BBS Ltr. #77-189 50-249/1977-3 | |
| Download: ML17252A280 (3) | |
Text
Commonwr*h Edis.on One First Nstic9F>1aza, Chicago, Illinois Address Reply to: Pos.t Office Box 767 Chicago, Illinois 60690 BBS Ltr. #77-189 March 9, 1977 Mr. James G. Keppler, Regional Director tiirectorate of Re~ulatory Operations - Region U. S. N_uclear Regulatory Commission III 799 Roosevelt Road Glen Ellyn, Illinois Enclosed please find Reportable Occurrence report number 50-249/1977-3.
This report is being submitted to your office in accordance with the. Dresden
. Nuclear Power Stati()n Technical Specifications,. Section 6,- 6 :B.
BBS :jo Enclosure
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B'. B. Stephenson Station Superintendent Dresden Nuclear Power Station c,c:. Director of Inspection & Enforcement Director of Management Information & Program Control File/NRC *
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LICENSE NUMBER fPLcJ\\SE PAINT ALL Rt.:GUlRED li\\lFOR!VIAitf:
e LICENSE EVENT
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8 9 15 25 26 30 31 32 CATEGORY
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B 57 58 REPORT BATE
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EVENT DESCRIPTION
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8 g During normal operation 1 APPJ1 116 indication appeared to be _registering power le_v_e,,_l __
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[OJ~ l__fluctuations of 6 - 10%.
7 B 9 In the course of _investigating this condition, all APRH
[o14J I*. averaging card relays were checked for ~Jroper ooeration. ___{2.Q:-249/1977-3) 7'.'89
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The indication. *fluctuations. on APRM 116. were found to haye been caused by.mar-
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@"ffil I ginally functional reed relay contacts on the APRM If 6 averaging card.
The reed l
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e*:t ITEJ I:. r~lay contacts were replaced, and the APRk 116 a:veraging card circuitry was tested 1
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B~l FACrUTY
. METHOD OF.
- STATUS
.'JI> POWER OTHER *STATUS DISCOVERY
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7,, 8 DISCOVERY DESCRIPTION NA ____________ f 46 ea FORM OF ACTIViTY CONTENT
. RELEASED L~J OF RELEASE AMOUNT OF ACTIVITY
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10 11 44 LOCATION OF RELEASE.
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PERSONNEL. EXPOSURES NUMBER.
TYPE o:esCRIPTION ETil l o I o I ol W 7. 8. 9 11
- 12 13 PERSONNEL INJURIES NUMBER EEi I o I ol ol pESCRIPTION NA l
7" 8* 9 11 12 80
.OF.FSITE CONS.EQUENCES i1*j5j;,. *.
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80 LOSS. OR. DAMAGE TO, FACILITY TYPE DESCRIPTION EEl~ I NA 7
8 9 10 80 PUBLICITY r:;r:;t,.
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B 9 80 ADDITIONAL FACTORS.
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CAUSE DESCRIPTION=--(Continued) satisfactorily.
The discovery of an averaging card circuit problem on APRM 116 prompted an operability check of the remaining APR.~ averaging cards.
During this check 'it was discovered that the reed relay contacts on relay Kll (which connects the LPRH 16-09B input to averaging card Z29 of APRM 115)' appeared to be physically separated.
As a result, upon coil energization, the contacts-closed but failed to touch.one another, thus preventing the LPRM 16-09B input from entering* the averaging cir-
. cuitry of APRM 115.
Furthennore, 15 additional LPRM input-related relays on Unit-3 were found to exhibit higher-than-average* contact resistance.
_As stated previously, the marginally functional reed relay contacts identified for APRM 116 were replaced, as were the fa:i,l ed' relay contacts for APRM 115 (both units.are General Electric Co. type GE 176Al405P003 components).
The 15 Unit-3 LPRM's associated with the above-mentioned relays have been-bypassed pending the receipt of additional relays (which are presently on order).
This action was taken as a matter of good operating practice.
Since all APRM's on Unit-3 still retain more than the required.number of LPRM*inputs, this event is considered*
to be of little safety significance.
To ensure timely identification of any recurr'ing failures, the Unit-3 APRM averaging card.relays will be checked again in approximately one year's time.
. Although a similar relay failure was* subsequently identified on Unit-2, this was
- tl:ie first reported failure of this nat:ure at D:r::esden.