ML20058C007
| ML20058C007 | |
| Person / Time | |
|---|---|
| Site: | Maine Yankee |
| Issue date: | 10/24/1990 |
| From: | Nichols S Maine Yankee |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| RTR-REGGD-01.097, RTR-REGGD-1.097 MN-90-108, SEN-90-297, NUDOCS 9010310192 | |
| Download: ML20058C007 (4) | |
Text
e MaineVankee atuana escinctv som wa,s t sws 'er:
e PO Box 408. WISCASSET. MAINE 04s78. (204 887 4321 October 24, 1990 SEN 90 297 MN 4 108 US Nuclear Regulatory Commission Washington DC 20555 Attention: 100cument; Control, Desk
References:
(a) License No. DPR 36 (Docket No. 50-309)
(b) MYAPCo Letter to USNRC dated February 23,28, 1985 (MN 85 43)
(c) USNRC Letter to MYAPCo dated April 1989
Subject:
Reg Guide 1.97 CONTAINMENT INTEGRITY VALVE INDICATION Gentlemen:
On October 20, 1990 with the plant at 0% power and at hot standby, it was noted that all of the lights on both channel A and channel B Engineered Safety Feature (ESF) valve position indication light boxes were dimly illuminated.
These light boxes provide ESF valve position indication, including the status of containment isolation valves.
Normal operation is unilluminated for an open valve and illuminated for a closed valve.
In each case when a valve is shut, its position indication light became brightly illuminated.
The dimly illuminated light indication implied problems and tests were conducted to verify function by.
shutting additional valves.
Investigation revealed a failed biasing diode in the circuit for one valve.
When the failed diode was replaced, normal light box indication was restored.
l Further investigation was conducted to determine why a single component failure had an ef fect on the two separate valve position lndication boxes.
It was I
then revealed that both 00xes received power from a single non 1E power source which does not conform with Maine Yankee's commitments to Regulatory Guide 1.97, Reference (b).
Specifically, the valve indication for the 27 valves listed in the attachment does not meet single failure Criteria.
1 The valves in question have position indication on the main' Control board ECCS light box, the Engineered Safety Feature (ESF) panel and the plant computer.
Failure of any portion of the light box or associated indication systems will not prevent the valves from performing their safety function as the light box circuits are electrically independent from all safety related valve control circuits and actuation logic.
It can be postulated, however, that a single failure can disable each means of indication.
i
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9010310192 901024 PDR ADOCK 05000309 S
PDC h
t
Oc'tober 24. 139)
Page two e
Failure of the light box system is detectable in both the energized and de energized states.
A short or ground in the system resulting in a loss of light box power can be detected by observing that the lamp test ci" cult fails to illuminate the windows when the push button is depressed.
A failure Causing all windows to illuminate, regardless of valve position. can be detected bv observing that spare window locations are also illuminated.
Nonetheless we have reviewed the potential safety significance of not having main control board indication for the subject containment integrity valves.
The valves listed in-the attachment are associated with 19 separate pipe i
In the Case of six penetrations. the air operated valve is the v
redundant isolation to a membrane; barrier in the containment, such as a recirculating fan cooler heat exchanger - Four penetrations have redundant check valves.
The check valves are regularly subjected to inservice testing and there is no reason to question their operability.
One other containment penetration has redundant isolation valves.
One valve has qualified position indication on the main control board. The second valve has position indication on the ECCS light Box. The remaining 8 containment penetrations have two valves that are used to isolate the pipe for containment isolation.
Both of the valves are powered from redundant power supplies. _ However, these. valves have their position indication-located on the light boxes by trains.
A single failure of tne power supply could prevent the indication of both valves.
Following detection of a light box failure. Containment-Isolation Valve positions may be verified by:
Those valves which do not have independent indication and are located outside of containment may be verified closed by operator inspection, or by closure of other penetration isolation valves.
The remaining valves without independent indication can be verified closed by performing a continuity test through the valve limit switches at terminal blocks in the main control board.- Terminal blocks with disconnect = capabilities are provided for each limit switch terminal point such that the limit switch may be isolated from the light box circuits.
Maine Yankee believes that continued operation is justified.
This bel'ief is based on the following:
P 1.
The likelihood of an accident requiring containment. isolation combined-with a failure of the control board light indication'is' extremely remote.
2.
Most of the containment isolation valves have two independent position indications. Onl depend solely on y a small number of containment isolation valves the light box for indication.
l i
e I'
s
1 October 24. 1990 Page three 3.
The general design criteria Jfor containment' isolation i met:since a failure of the position indication circuitry.does not _r.
ult-in a f ailure of an isolation. valve' to perform its: safety fun '. ion.
4 The closed position of all outside containment isolation valves can be visually verified.
S.
The position of the seven isolation valves located in' side the containment whose position is indicated on the light box can-be-verified closed by.an electrical continuity check.
Maine Yankee plans to institute the following administrative controls:
a.
In the event of an accident requiring containment isolation operators:
will be instructed to verify shut the'outside containment isolation valves. A list of the affected valves and their. location has.been provided to the control room operators, Operators will be instructed.to c'eck the. status-of the ECCS. light box b.
h once per shift.
c.
Operators will be alerted to the single f ailure vulnerability _ of E he -
t light box prior to assuming watch duties Maine Yankee plans to complete a design change to resolve _this condi. tion during the next scheduled refueling' shutdown.
We trust this information is satis 1*actory..Please contact me should you-have any questions regarding.this matter.
Very truly yours.
'$b
..S. E. Nichols Licensing Section Head sen/cfh Attachments C:
Mr. Thomas T. Martin Mr. E. Trottier Mr. Charles Marschall h
q
OCT 24 '90 13:19 YRKEE BOLTON p
p0NTAntMENT PENETRATIONE INDic1TED gg 33Z PNAEIA l
YALVE M MEMBRAME PENETRATIDMS VALVE No.
PEN.
ESF PANEL NEMBRANE BD-T-12 47A A
STRAN GENERATOR 1 BD-T-22 475 A
STRAN GENERATOR 2 BD-T-32 47C A
STRAM GENERATOR 3 PCC-A-216 81 B
PIPE PENETRATION COOLING HPD-A-17 64,65,66 B
STRAM GENERATOR 8 HPD-A-96 64,65,66 A
STRAM GENERATOR 8 t
yALYE gg CHEgg YALYE PENETRATIONS VALVE No.
PEN.
EST PANEL CHECK VALVE IA-A-107 59 3
IA-109 N-A-66 44 5
N-29 PW-A-78 37 B
PW-80 SA-A-138 48 3
BA-139 YALYE MD YALYE RENETRATIONE l
VALVE NO.
VALVE No.
E8F PANEL C-A-14 A
LI-A C-A-15 B
60 IA-A-98 B
IA-A-101 LN-A-45 B
61A LM-A-43 B
PCC-A-252 A
6 PCC-A-254 B
PCC-A-268 A
89 PCC-A-270 B
PCC-A-300 A
5 PCC-A-302 B
PD-A-122 A
92 PD-A-124 B
PR-A-40 A
39 PR-A-41 B
PV-A-10 A
24 PV-A-12 B
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