ML19220C704
| ML19220C704 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 04/20/1979 |
| From: | Carbon M Advisory Committee on Reactor Safeguards |
| To: | Gilinsky V NRC COMMISSION (OCM) |
| Shared Package | |
| ML19220C699 | List: |
| References | |
| ACRS-R-0827, ACRS-R-827, NUDOCS 7905140053 | |
| Download: ML19220C704 (2) | |
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UNITED STAT ES rt' ;- (7j' sg NUCLEAR REGULATORY CCMMISSION M ~Q'7.. l ADVISORY COMMITTEE ON REACTOR SM EGUARDS
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April 20, 1979 Hor.orable Victor Gilinsky Auting Chcir:2n U. S. Suelear Regulatory Cecmission b:ashington, DC 20555 C-mar Dr. Gilinsky:
?.is letter is in resp:n.te to yourr. of April 18,1979 '..hich requested that the ACFS notify the Commissicners i=ndiately if W believe any of car er:1 recccaridations of April 17 should be acted up:n before our nen. regularly scheduled meetire3 at sich va could c. retare c fo :al 1
. letter. The Comnittee discussed this topic by conference telephcne cc11 en' April 19 and offers the fc!!cwirg ec= ants.
All cf the rec c.:ndatfons made by the AC7:S in its meetir,g with the Ccc..R cicnces en April 17, 1979, are generic in nature red cpply to all F',Gs. #:ne were intended to recuire i:r.Tediate changes in oper: ting pro-
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e:<duros or plcnt codificatiens of cperating P.G.I.
Such changes sh:LO.d bc.rede cnly after study of their effects on over.all safety.
Su;h stud-ie.c ch:t.M be ede by the licensees and their suppliers or consultads and by the IGC Staf f.
7he Comittee beliwes that these studies should b-beg' 1 in the near future on a time scale that will not divert the -
!!RC Staff or the industry representatives frem their tasks relating to the coold:.,n of Taree P.ile Island Unit 2.
Fi: wever, t!>e Cc.i.mi ttes be-
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lievcs that it vould be pessible and desirable to initiate 1::aediately a cu vey of cocratire proceduces for achievire natural circulatien, in-clufirg the case den offsite power is lost, and the role of the pres-curi:er heaters in such procedures.
I.: its :nct'Ing en April 15 and 17, 1979, the Ce mittec discussad.uith e ERC St.aff the f.',atter of natural circulatica for the 7nree Mi.T.c Is-
.' a-d Uni t 2 pla.nt.
Tne C =.ittee belicves that this =tter is receiv-
,'n:. c;reful attentiori b' tha 1GC Staff and the licensee.
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To E00 for.cppropri.ite Action.
Distribution:
Chm, Cars, FE. OGC, OCA, SELY, 5 3, OIA.
Rapi fc xc d to EDO, PA, E. Case.
79-1117.
101 141 7Dosisoos3
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ii'ec.rable Victor Gilinsky Iq@ril 20,1979 Tn; Cc.walttet's cwn recm ncidations to the Cc:caission on April 17 scre
- e. t interded to apply to Tarce Mile Island Unit 2.
w'3 plan to write a further re;: ort en these matters nt our Fa.y lo s 1979 tac:.tirig.
Sincerely,
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a rbon Chair.an
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P 101 142
pa atcog U.'.'ITED STAT ES E
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( i NUCLEAR REGULATORY CO..', MISSION
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ne ADVISORY COf'.f.'.lTTEE OfJ REACTOR SAFCGUARDS k i #( f f
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WASHINOToN. O. C. 20555 April 18, 1979 MEMORA'!DUM rTR: Chaiman Hendrie Commissioner Gilinsky Cornissioner Kennedy Cornissioner Bradford Comaissioner Ahearne FP^i4:
R. F. Fraley, Executive Director Advisory Committee on Reactor Safeguards Attached for your infomation and use is a copy of the recommenda-tions of the Advisory Ceraittee on Reactor Safeguards v.hich were orally presented to and discussed with you on April 17, 1979 re-garding the recent accident at the Tnree Mile Island Nuclear Sta-tien Unit 2.
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R. F. Fraley Executive Ditector At tachm.ent:
Recem=cndations of the NRC Advisory Com:nittee on Reactor Safeguards Re. the 3/28/79 Accident '
at Tne Three Mile Island Nuclear Station Unit 2 DUPLICATE DOCUMENT 101 1!3 Entire document previously entered hl into system under:
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UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, DC 20555 APRIL 21, 1979 IE Bulletin 79-05B NUCLEAR INCIDENT AT THREE MILE ISLAND - SUPPLEMENT Description of Circumstances:
Continued NRC evaluation of the nuclear incident at Three Mile Island Unit 2 has identified measures in addition to those discussed in IE Bulletin 79-05 and 79-05A which should be acted upon by licensees with reactors designed by B&W.
As discussed in Item 4.c. of Actions to be taken by Licensees in IEB 79-05A, the preferred mode of core cooling following a transient or accident is to provide forced flow using reactor coolant pumps.
It appears that natural circulation was not successfully achieved upon securing the reactor coolant pumps dur.ing the first two hours of the Three Mile Island (TMI) No. 2 incident of March 28, 1979.
Initiation of natural circulation was inhibited by significant coolant voids, possib!
aggravated by release of noncondensible gases, in the primary coolant system. To avoid this potential for interference with natural circulation, the operator should ensure that the primary system is subcooled, and remains subccoled, before any attempt is made to establish natural circulation.
Natural circulation in Babcock and Wilcox reactor systems is enhanced by maintaining a relatively high water level on the secondary side of the once through steam generators (OTSG).
It is also promoted by injection of auxiliary feedwater at the upper nozzles in the OTSGs. The integrated Control System automatically sets the OTSG level setpoint to 50% on the operating range when all reactor coolant pumps (RCP) are secured.
- However, in unusual or abnormal situations, manual actions by the operator to increase steam generator level will enhance natural circulation capability in anticipation of a possible loss of operation of the ~ reactor coolant pumps.
As stated previously, forced flow of primary coolant through the core is preferred to natural circulation.
Other means of reducing the possibility of void formation in the reactor coolant system are:
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Minimize the operation of the Power Operated Relief Valve (PORV) on the pressurizer and thereby reduce th-
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reduction by a blowdown through a POR DUPLICATE DOCUMENT 1 0 1 i n,,
Fntire document previously entered into system under:
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