ML20084R602

AO 50-249/75-08:on 750218,during Routine Calibr of Level Switch LIS 3-263-57B,setpoint Found Above Tech Spec Limit. Caused by Instrument Setpoint Drift.Switch Tested for Repeatability & Performed within Manufacturer Limits

ML20084R602
Person / Time
Site:	Dresden
Issue date:	02/27/1975
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML20084R604	List: ML20084R602 ML20084R606
References
120-75, AO-50-249-75-08, AO-50-249-75-8, NUDOCS 8306150225
Download: ML20084R602 (2)

Text

/ -

Comm e:lth Edison (N

• * , h' one rust tonal _Plata. Chicago. Illinois h

' (h</ Address ReplyIllinois Chicago, to: Post 60690 Olfica Box 767

• v-BBS Ltr. #120-75 Dresden Nuclear Power Station R. R. #1 g Morris, Illinois 60450'>'( N ..

February 27, 1975 /V CiPh ' 3

/l'pk:'LUlI3 h, W M 1975 N -)

Mr. Janes G. Keppler, Regional Director Gl a ;f][

/- Directorate of Regulatory Operation-Region III ' I t ,

q c. w }G i

t U. S. Nuclear Regulatory Co:I:::tission g# j 799 Roosevelt Road f ,. s, L- Glen Ellyn, Illinois 60137

SUBJECT:

REPORT OF AP. NORMAL OCCURRFUCE PER SECTION 6.6.A OF THE TECHNICAL SPECIFICATIONS ISOLATION LEVEL SWITCH SETPODE DRIPP

t.

References:

1) Regulatory Guide 1.16 Rev 1 Appendix A

2) Notification of Region III U. S. Nuclear Regulatory Co:nnission Telephone: P. Johnson, 1600 hours0.0185 days <br />0.444 hours <br />0.00265 weeks <br />6.088e-4 months <br /> on February 19, 1975 Telegram: J. Kcppler, 1625 hours0.0188 days <br />0.451 hours <br />0.00269 weeks <br />6.183125e-4 months <br /> on February 19, 1975

3) Drawing Number 12E2501 b Report Nu:nber: 50-249/75-8 e Report Dates February 27, 1975 g Occurrence Date: February 18, 1975 L Facility: Dresden Nuclear Power Station, Morris, Illinois

( IDETIFICATICN OF OCCURRENCE L Reactor low level isolation instrument setpoint above technical specification limit k as found in tabic 3 2.1.

CONDITIONS PRIOR TO OCCURRENCE Dresden Unit 3 was in cold shutdown with core spray piping inspection work in progress.

Routine surveillance was being performed by the Instrument Departanent.

~

DESCRIPTION OF OCCURR GCE During routine calibration of level switch LIS 3-263-57B, the setpoint was found at 115 inches H2 O op increasing, which is above the Technical Specification Limit of

equal to or less than 114.3 inches H 2O 4 p increasing. (114.3 inchos H2O Ap is 8306150225 750227

{DRADOCK 05000249 n00 PDR-MAR -3 1975 s

o ,, f)

M. Ja_ mes G. K:pplcr' February 27, 1975 equival.cnt to 143 inchos of H 2 O above the top of the active fitel). The switch was in:nediately reset to 112.1" H 20 Ap $ncreasing. ..

l DESIGNATION OF APPARENT CAUSE OF OCCURRENCE (Equipment Failure)

The apparent cause of tho occurrence was instrwuent setpoint drift.

3 AtutLYSIS OF OCCURRD CE 4 Level switch LIS 3-263-57B is one of four switches that function to isolate the reactor. The switch was found to be only 0 7 inches below the required cotpoint.

The remaining switches were checked and found to operate well within the Technical Specification limit. Reactor isolation, if required, would have occurred within the Technical Specification limit by actuation of the other switches and it is therefore concluded that the safety of plant personnel or the general public was in no way jeopardized as a result of this occurrence.

CORRECTIVE ACTION i The switch was tested for repeatability and performed well within the manufacturers limits. It was observed that the mercury bulb could be moved in its holder, which indicated that the factory applied adhesive had deteriorated. This condition was corrected by applying new adhesive and the switch was reset to comply with the

- Technical Specifications.

3 FAILURE DATA This is the first instance of setpoint drift for this switch. Yarway level I

indicating switch failures has occurred in the past, report number 50-237/75-1 and 50-237/75-7, however the approximate cause for these occurrences is different than that of this occurranco.

LIS-3-263-57B is a Yarway Model 441BC Level Sensor with a 120 inch rance and 2%

accuracy.

Sincerely,j M

B. B. o ens n Super endent BBS:smp File /AEC b- _