ML20168A458

Final ASP Analysis - Dresden 1 (LER 010-70-LTR)

ML20168A458
Person / Time
Site:	Dresden
Issue date:	06/16/2020
From:	Christopher Hunter NRC/RES/DRA/PRB
To:
Littlejohn J (301) 415-0428
References
LER 1970-LTR-00
Download: ML20168A458 (4)

Text

ailure of Three of Four Safety System Sensors for Primary Drum Low Level resden 1 sequence was:

outine test, three of four primary drum low level scram system sensors failed due to crud build-up in the switches. These failures would ilure to scram on low drum level if that were required.

action:

s were flushed and their proper operation was demonstrated. The switches replaced with differential-type switches at the up-coming refueling, ose of failed system or component:

s provide trip input to the scram system for primary drum low level.

ity of system per WASH 1400:

• ity of component per WASH 1400:

• float switches not considered in WASH- 14 00 ilabilities are in units of per demand D-1. Failure rates are in r hour HR'1

(Reactor condition IThree of four primary Potential unknown) testing drum low level scram Severe in progress jswitches found failed Core Damage No - scram on primary drum low level not required No NSIC 44751 - Actual Occurrence for Failure of Three of Four Safety System Sensors for Primary Drum Level Scram at Dresden 1

I - No Yes No LII Yes Yes NSIC 44751 - Sequence of Interest for Failure of Three of Four Safety System Sensors for imary Drum Level Scram at Dresden 1

N NUMBER: 44751 April 27, 1970

unknown ED: Reactor Protection System OLVED: Primary Drum Level Float Switches d buildup in the float chambers NTEREST: Loss of Main Feedwater ENCE: Switch failure during testing Dresden 1 50-10 BWR ICAL RATING: 200 MWe 10.5 yr INEERS: Bechtel Commonwealth Edison Co.

ine miles E of Morris, Ill.

0 (a) hours G CONDITION: unknown E TYPE OF FAILURE: (a) inadequate performance; (b) failed to start; QDmade inoperable; (d) ___________

HOD: during testing ly abstract available