ML19224C926

Forwards Extracts from Chronology of 770942 Event & Sequence of Events Re 750613 Incident

ML19224C926
Person / Time
Site:	Davis Besse
Issue date:	05/03/1979
From:	Wright R Advisory Committee on Reactor Safeguards
To:	Advisory Committee on Reactor Safeguards
References
ACRS-SM-0107, ACRS-SM-107, NUDOCS 7907100238
Download: ML19224C926 (1)

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M Uhyy ADVISORY COMMITTEE ON REACTOR SAFEGUARDS NUcLEAn nEGULATORY COMMISSION W ASHINGTON. D. C. 70%5 lby 3, 1979 ACn3 t' embers ACPi3 Technical Staff

SUBJECT:

CHRO: OLOGY OF' TiiE SFWDiBER 24, 1977 DAVIS-BESSE 1 EVEtJT Dating discussions inong ACP.S staff menbers the question of conditions under which steca could f orm in the RCS of BLW reactors arose.

It is believed that steam did form in the primary during the course of the Davis-Besse 1 event of September 24, 1977.

I have extracted the at-tached per tinent pr>ints f t co the chr onology of that event. You may finn it of use in your study of 'U4I.

funy of the circumstances in the Davis-Besse 1 event

• ure similar to the T4I accident.

In fact, had the PORV block valve not been closeJ coon af ter it stuck open, the conse-ouences might have been very sericus. A complete discussion of the tvent is included in the referenced letter. Rich f42jor will have a copy of it aftet I leave.

I have also attached a sequence of events for the Oconce 3 event of June 13,1975 when the PCRV stuck open. tb detailed chronology or investigation of this event was made.

Rich Itajor also has a copy of the LER for this event.

Pobert _. Uright Staff Engineer Attachments:

1.

Dettinent Points from the Chronology of the 9/24/77 Davis-bcsse 1 Event 2.

Eequence of Events of the 6/13f/S Oconce 3 Event

Reference:

Ltt., T. D. k'.ur r ay,

Davis-Pesse tbclear Station to J, G. Keppler, I&E, dtd. ll/14f/7 Jjg cc:

m4: Stcmuittee Consultants J J !,

7907100238'

a, ADVISORY COMMITTEE ON REACTOR SAFEGUARDS fJUCLE AR RFGULATORY COM;AESIOfJ w ASHirJGTON. D. C. ;rGZ5 tby 3, 1979 ACRS Members ACRS Technical Staff

SUBJECT:

CHRONOLO3Y OF Tl!E SEPT mBER 24, 1977 DAVIS-BESSE 1 E"E';T Dur ing discussions mong ACRS staf f mcmbers the (;uestion of conditions undet which stema could form in the RCS of B&W r eactors ar It is believed that steaa did form in the pt iraary dur ira the cod.ose.

e of the Davis-Besse 1 event of September 24, 1977.

I have extracted the at-tached pet tinent points from the chronolugy of that event. You ray find it of use in your study of D:I. f uny of the circumstances in the Davis-Besse 1 Event were siiailar to the 31I accident.

In fcct, had the PORV block valve not been closed soon after it stuck cpen, the ccnse-quences might have been very ser ious. A complete discussivn of the evenc is included in the referenced letter. Rich Major will have a copy of it af ter I leave.

I have also attached a sequence of events for the Ceonce 3 cvent of June 13, 1975 when the PORV stuck open. No detailed chrone' Jy or investigation of this event was made.

Rich Major also has a copy of the LER for this event.

Rolar t L. WIight Staff Engineer Attachments:

1.

Pettinent 11;ints from the Chr onology of the 9/24/77 Davis-Besse 1 Event 2.

Ecquence of Events of the 6/13/75 Oconae 3 Event

Reference:

Tcr., T. D. Murray, Davin-Ben se Nucleat Station to J. G. Meppler, I&E, dtd. 13/14/77 cc: DiI Subcocaitt ce Consultants n

x EXTRACT FRG1 CllRONO!L3Y OF D.WIS-DESSE 1 EV!:NT OF SEI'I' EMBER 24, 1977 (RE/C1'OR AT 9% POh'ER)

TIME ACTION RF3d3ON O

1/2 trip in SFRCS Spur ious low level EI; 2 S

58 Complete SFRCS trip s

1" 6 PORV opened & cycled 2255 psig 9 times & Icmained open S

1" 47 Operator tripped taactor Picssutizet level rose to 209 in.

2" 57 HPI initiated RCP = 1600 (automatically) 6" Quench tank topture disc DORV open ruptured m

s 6 14 Operator stcppc.d HPI High pr essor izer level 8"

Steam formation in RCS Satur ation Pressure (measut ed 65 f t. top of cor e and extr apolated to core) 9" 2.s Operator stopped 1 RCP Reduce neat input to RCS in each loop m

PORV block valve closed gy 41" 2nd makeup ptrap started To stop pr ensur izer level dectease 43" PI essur izet heaters Restore pressorizer lecel cut off U

53" 24 J2 HI>I pump stopped Pr essor izer level increasing 57" Mieup r estot el to normal, normal cooldtA/n started T

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SEQUENCE OI? EVENTS CCONEE 3 EVENT JUNE 13,1975 ACTION REASON Oper ator placcd tur bine control Opeator Error station in rnnual ICS could not control feedwater flow Rapid increase in unit load demand 103V opened and stuck open RCP 2255 psig due to oscillating steam generatot level and feed-watet flow Reactor trip and liPI initiated Iow RCP pr essur e PORV isolation valve closed PCRV isolation valve reopened Rising pressuriner level CJench tank tupture disc roptuted PORV open PORV isolation valve closed RCP 800 psi (transient terminated) e on

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