NUREG/CR-2083, Forwards NUREG/CR-2083, Evaluation of Threat to PWR Vessel Integrity Posed by Pressurized Thermal Shock Events. Joint Ofc of Nuclear Reactor Regulation/Ofc of Research Team Will Review Rept.W/O Encl
| ML19270A274 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 10/09/1981 |
| From: | Dircks W NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO) |
| To: | Bradford P, Gilinsky V, Palladino N NRC COMMISSION (OCM) |
| Shared Package | |
| ML19270A275 | List: |
| References | |
| NUDOCS 8110280123 | |
| Download: ML19270A274 (4) | |
Text
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October 9,1931
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m"'RAUDUti FOR:
Chaiman Palladino Commissioner Gilinsky Conraissioner Bradford
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Corcissioner Ahearne T
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Comissioner Poberts
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Pilliam J. Dircks b
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Executive Director for Operations
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SUBJECT:
STATUS REPORT M PPISSURIZED TFEM AL SHOCK r
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'G In informtion paper SECY-Sl-286 on pressurized themal shock of pressdr$g vessels and in the subsequent briefing of the Concission on June ll,1M the Comnission.as inforned that Oek Ridge Naticnal Laboratory was pre-paring a status report on pressurized themal shock.
f.n interim report focusing on Oconea-1 has now been completed; a preprint copy is enclosed.
As noted in the enclosed report, the purposes of this ORNL work are to identify what is presently known about this preMen including najor arcas of uncertainty and sensitivity, to identify further infomation needs, and to propose and evaluate possible nitigative neasures. This interin report creanizes what is presently known and presents a preliminary assessnent, based on present analysis, of the threat of pressure vessel failure.
Althouah the no linal calculations indicate a proximate threat, the report points out a nunber of flaws in the current themal-bydraulic analysis which reflect a leck of realism. The ouner of the plant, Duke Power Co., was esked to review the analyses for accuracy; the Duke representatives also challenged the validity of currently available analyses.
In order to cvaluate the conclusior-of the report and to assess their significance, a joint NRP/CES teau.ias been set up to review the report as soon as it arrives in 4RC.
In perticular, the steff will evaluate the probabiliW of occurrence of the severe overcooling transients assumed and
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The Comissioners the conservatisms used in other portions of the Oak Ridge analyses. Tha team v:lli be led by the NRR task manager, Roy Woods, and it plar.s to con.-
plete its assessment with a draft report in 2 weeks.
We will keep the Comission infomed of the results of this review.
%d Willin j,g;g William J. Dircks Executive Director for Operations
Enclosure:
NUREG/CR-2083. Evaluation of the Threat to PWR Vessel Integrity Posed by Pressurized Thermal Shock Events cc w/ enc 1: PDR cc w/o enc 1: SECY OPE OGC Distribution:
RES Central File CIRC CHRON DRA Reading DRA Subject Bernero Reading Murley Copy Dircks Copy EDO r/f rs Tamph o"'c t > RES/DM/S REXX JI DST 'D EDO RBekf;pst.. u r.l ey..
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MEMORANDUM FOR: Chairman Palladino Commissioner Gilinsky Commissioner Bradford N
Commissioner Ahearne Commissioner Roberts FROM:
William J. Dircks Executive Director for Operations
SUBJECT:
STATUS REPORT ON PRESSURIZED THERMAL SHOCK
'N In information paper SE 81-236 on pressurized thermal shock of pressure vessels and in the subsequeqt briefing of the Commission on June 11, 1981, the Commission was informed t(at Oak Ridge National Laboratory was pre-paring a status report on pressurized thermal shock. An interim report focusing on Oconee-1 has now bee'n completed and will soon be sent to NRC.
Although the staff has not reviewed the report, the major results were recently discussed with ORNL in a confhrence telephone call. The staff understands that ORNL has considered a lla(ge loss-of-coolant accident (LOCA) and a spectrum of steam line break accidents to generate pressure and temperature vs time curves as input for' fracture mechanics calculations.
Some of the assumed steam line break accidents'\\apparently result in over-cooling conditions considerably more severe thair those in the Rancho Seco s
transient of March 1978, which the staff has beenNsing as a benchmark transient for fracture mechanics calculat',as.
The staff further understands that, for the most severe vercooling trans-ients investigated, the fracture mechanics calculations pNedict vessel cracking at an earlier time in the life of the Oconee-1 pla'nt than pre-s dicted for the Rancho Seco transient. Representatives from Duke Power and Babcock & Wilcox have had an opportunity to review the draft report at the request of RES. The Duke Power representatives believe that many of the assumptions in the thermal hydraulics calculations are unrealistically conservative.
In order to evaluate the cor.clusions of the report and to assess their significance, a joint NRR/RES team has been set up to review the report as soon as it arrives in NRC. In particular, the staff will evaluate the probability of occurrence of the severe overcooling transients assumed and the conservatisms used in other portions of the Oak Ridge analyses. The team will be led by the NRR task manager, Roy Woods, and it plans to com-plete its assessment with a draft report 2 weeks after receipt of the repo rt.
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4 The Comissioners We will keep the Comission informed of the results of this review.
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