ML20084P824

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AO 50-249/75-28:on 750522,main Steam Line Area Temp Sensors 261-16B,261-17 A-D & 261-18D Found W/Setpoints Above Tech Spec Limit.Caused by Misapplied Switches.Switches Reset within Tech Spec Limit
ML20084P824
Person / Time
Site: Dresden Constellation icon.png
Issue date: 05/30/1975
From: Stephenson B
COMMONWEALTH EDISON CO.
To: James Keppler
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
332-75, AO-50-249-75-28, LER-75-28, NUDOCS 8306130045
Download: ML20084P824 (2)


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>fTs ,Commony alth Edison 6 . , ff a ; one p,,3 us ,i pnfa en,cago. Ithnca,s E .hC/, Ao:fress Rhp/to: Post O!bcc Box 707 d ,

-# Chicago. lihnois 60690 BBS Ltr.-#332-75 Dreeden nuclcar Power Station . 1 1

R. R. #1 -

Morris, Illinois 60450 i May 30, 1975 (Utg ,y ,

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3 Mr. Jamen G. Keppler, Regional Director '

Directorato of Regulatory Operation-Region III ,

U. S. Nuclonr Regulatory Comissicn -

799 Roccovelt Road Glen Ellyn, Illinois 60137 SUB.1ECT: REPORT OP_. fdE!ORMAL OCCURRF: CE PER SECTION 6.6. A OF THE TECH!!ICAL

. SPECIFICATI0DS_ ,

MAIN STCOI LINE HI-TZMP SNI'KH SEPPOD?P DRIFP Roferences: 1) Regulatory Guide 1.16 Rev. 1 Appendix A

2) Notification of Region III of U. S. Nuclear Regulatory Co:cniccion Telephone: P. Johncon, 1400 hours0.0162 days <br />0.389 hours <br />0.00231 weeks <br />5.327e-4 months <br /> on May 23, 1975 Telegram: J. Keppler, 1450 hours0.0168 days <br />0.403 hours <br />0.0024 weeks <br />5.51725e-4 months <br /> on May 23, 1975 I
3) Drawing Nu:::bcr 12E2501 Roport Number: 50-249/1975.28 Report Datos May 30, 1975 s Occurrence Date: May 22, 1975 Facility: Dresden Nuolcar Power Station, & rrio, Illinois 60450

_IDDiPIPICATION OF OCCURRE!CE ,

Main Steam Lino (MSL) Area Temperature Sensora 261-16B, 261-17 A-D, and 261-18D vero found with setpoints above the 200*P technical opecification limit.

CONDITION PRIOR TO OCCURRE CE Unit-3 was in the chutdown modo in a refueling. outage. ,

pesCRIrrIon oP oCCUnan:CE-On May 22,1975, during the routino scheduled calibration of the MSL area temperature censoro, the sotpoints woro found to be above the 200*F limit. The reactor was chutdown with the head rcmoved. .

8306130045 750530 PDR ADOCK 05000249 '

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O Mr. Jamea O. Ktppler May 30, 1975- .

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O O DESIGNATI0'i OF APPiMEN'P CAUSE OF 000URRE!0E (Design Error)

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

ANALYSIS OP OCCURRD'CE The function of tho temperature sensors is to isolate the main steam lines in 4 the event of a steam leak $n the outboard Main Steam Line Isolation valvo area. I The "as-found" sotpoint of the 16 stritches involved would have provided an isolation at 184*F (within the tech. specs limit). It is therefore concluded that tho safety of the plant personnel and the general public was not jeopardized as a result of this occurrence.

CORRIX:TIVE ACTION Inrnediate corrective action was' to roset tho switches to within the technical

.. specification limit.

To prevent a recurrence of this nature, a plant modification (412-3-74-175) will be mado after the liquid filled temperature sensors installed in the IIPCI area hevo been satisfactorily operated. Present data indicates that the liquid filled temperature sensor can be more accurately calibrated, assuring a consistent sotpoint.

FATIIJRE DA?"3

' Many actpoint violations have been discovered on Fenwal temperature sensors on both unita 2 & 3 Subsequent investigation has determined that the existing switches are nisapplied; an accurate "first operatien trip set point" cannot be consistently obtained. The manufacturer of the switches (Fenwal, Inc.)

has investigated the problem and has stated that existing switchco are not properly suited for a "first operation trip setpoint".

The switches involved are Fenwal Series 17000 hometically scaled thermo cw1tch type units. ,

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