ML20037B642
| ML20037B642 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 08/31/1976 |
| From: | Stello V Office of Nuclear Reactor Regulation |
| To: | Bolger R COMMONWEALTH EDISON CO. |
| References | |
| NUDOCS 8010270585 | |
| Download: ML20037B642 (4) | |
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E AUG 311976 Docket No.: 50-10 i::;=::
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i Comonwealth Edison Conpany ATTN: !!r. R. L. Bolger h-Assistant Vice President E==
Post Office Box 767 E+-
Chicago, Illinois 60690
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- p Gentlenen:
P.E: DRESDEtt STATIDM - UMIT t10.1
.;:gG In September 1973, The Atomic Enercy Commission published the " Technical Report on Anticipated Transients WIthout Scram for L'ater-Cooled Power
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Peactors" (HASH-1270) establishing acceptance criteria for enticipated
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transients without scrain ( ATWS). These criteria were oeveloped because we believed that a fully satisfactory nethodology for analyzin; the reliability of protection systens from the standpoint of comon node failures was not available at that time, that these types of failures i;:
had occurred in protection systems and that the potential consecuences of some postulated anticipated transients without scram cight be hazaracus to the public. - Subsequent to the publication of WASH-1270, we net with l} "
your Nuclear Steam Supply Systea Vendor, the General Electric Connany (GF),
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en a regt.?ar basis and reviewed their evaluation model, the results of analyses of anticipated transients without scrao, the diversity of the
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systems relied upon to mitigate the consecuences of ATUS, and the sus-R ceptibility of the Reactor Protection System to comon mode failure.
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In January of 1976, the status of our ATWS review and the ceneric analyses and proposals of GE were discussed before the ACRS.
A status report de-scribirr the infnrnation discussed is enclcsed.
Ue rennested fron GE additienal inforoation needed to co r,lete our neneric revic, m tMy i.
re ;wcer ty letter cated July 2,19E he intene in ec clet,<.ur revier of t:'ieir recort and fctomine any necessary plant chares as sosn as prac tic abl e.
In the interm, oased on our revies as cocr19ed in tu sis ut report, ~c 3elicve thn t"e addition of a recirculation nunr, trin vocle
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i significantly linit the consequences of an AWS event. CE took credit for
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a rvcirculation pump trip in the ATFS analysis they provided us and your referenced report, " Analysis of ATWS Consequences for Dresden, Unit - 1" (cover letter dated October 1,1975), also assumed a recirculation pump trip.
It is also our understanding that the recirculation pump trip
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w; described in your report has been removed. A trip of the recirculation pumps in the event of high reactor vessel pressure has the effect of causing an increase in the moderator voids in the reactor core. A substantirl
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negative reactivity results, and the power and pressure surges that might F
otherwise occur in the most' limiting transient (loss of condenser vaccuum) h are substantially reduced.
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We have found that a recirculation pump trip similar in design to the trip cescribed in the enclosed report and in General Electric Report NED0-20626 will provide substantial aaditional protection which is reouired for the public health and safety. Therefore we request that you inforn us of your commitment to modify your plant to provide a recirculation pump trip, and the schedule for doing so. We will review your detailed design to assure
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that the pump trip confoms to current regulatory practice and the description
-;.i-j in the enclosed status report. At least 90 days before your scheduled instal-lation, you should propose Technical Specifications for pressure and level F
setpoints for your recirculating pump trips and for surve11* lance recuirements.
Please provide us with the above infomation within 30 cays of receipt of this letter, including your schedule for submittinC the' cetailed design fer !P.C approval, your schedule for procurement, and your schedule for completion of
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modifications.
Sincerely, W
Original Signed by V Stello Victor Stello, Jr., Director
.,J Division of Operating Reactors
Enclosure:
DISTRIBUTION Status %ucrt on Anticipated N
CLZiemann Trensients Uit5 cut Scram for NRC PDR WEConverse CE Reactors - Decenner 9,1975 Local PDR PW0'Connor ORB #2 Reading RfiDiggs cc w/o enclo,ure:
See next page VStello DEisenhut KRGoller TBAbernathy TJCarter JRBuchanan Dross ACRS (16) 01 (5) ma:oa q o w p;ou n joR: s x:D1ya
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AUG 311976 Commonwealth Edison Company '
cc w/o enclosure:
Mr. John W. Rowe Isham, Lincoln & Beale Counselors at Law One First National Plaza, 42nd Floor Chicago, Illinois 60603
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