ML20209F841
| ML20209F841 | |
| Person / Time | |
|---|---|
| Issue date: | 09/09/1986 |
| From: | Russell W Office of Nuclear Reactor Regulation |
| To: | Bernero R Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20209C630 | List: |
| References | |
| FOIA-87-10 NUDOCS 8609120278 | |
| Download: ML20209F841 (3) | |
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UNITED STATES J[ T.. / i NUCLEAR REGULATORY COMMISSION
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September 9, 1986.
t MEMORAt:0UM FOR: Robert M. Bernero, Director Division of BWR Licensing, NRR FROM:
William T. Russell, Director i
Division of Human Factors Technology, NRP.
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SUBJECT:
GENERIC REOUIREMENTS FOR BWR CONTAINMENT RESPONSE TO SEVERE ACCIDENTS The Division of Human Factors Technology concurs with the technical content of your generic letter to BWR Licensees and Applicants on " Proposed BWR Severe Accident Containment Requirements (Generic Letter 86-
)."
We suggest, however, for the sake of clarity, that the editorial consnents on the enclosed marked-up copy be implemented.
1 bf William. Russell, Director Division of Human Factors Technology, NRR
Enclosure:
As stated cc w/ enclosures:
H. R. Denton R. H. Vollmer R. W. Houston G. C. Lainas H. L. Thompson i
G. Holahan J. L. Funches M. Srinivasan J. A. Zwolinski
- 0. R. Muller E. G. Adensam W. R. Butler l
B. D. Liaw f
M. W. Hodges L. Hulman
~ / g, D. B. Vassallo f01N
0 CONTACT: Millard L. Wohl, NRR (49-29853)
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ENCLOS &E UNITED STATES ecg\\
NUCLEAR REGULATORY COMMISSION
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- ,,..... /TO ALL BOILING WATER REAtTOR (BWR) LIC ig B0ILING WATER REACTOR LICENSES Gentlemen:
PROPOSED BWR SEVERE ACCIDENT CONTAINMENT
SUBJECT:
(GENERICLETTER86- )
l er Severe accidents doreinate the risk to the public assoc ence of Policy is,to take all reasonable steps to reduce >the chances of o plant accidents.
of such an accident should a severe accident and to mitigate the consequencesThe Reactor 4
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'the I.robabilities of accidents resulting in core melt were low, but d tended to cne occur.
containment perfomance following a severe accident was poor an Subsequent actions offset the benefits of low BWR core melt probabilitfes.
difications and resulting from the TMI Action Plan have led to several plant mo i
the likelihood required improvements in plant procedures to'further red accidents resulted in the fonnation of the Industry Degradedamaging of severe accidents.
.(IDCOR) group to address the concerns related to corevaluations 20COR effort has led to industry methodo7ogy for Indivess system reliab (IPEs) to search for the risk outMers and p The staff has concluded, containment performance on a plant sprJff. basis.
has been however, that for SWR containments,'a set of g t inment ld be possible via perfomance and will lead to speedier implemeMation than wou Severe accident analyses have indicated several areas for follows:
improvement in BWR containments which should be prompt the IPEs.
f Provisions should'be made for symptomatic urge that the 1.
and vent pa*is at set pressure conditions as a means to assure lead to cor.tainment pressure from beyond-design-b d
ath for l as a releases which will maximize the use of the suppression poo s
condensing and filtering medium.
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Provisions should be made for reliable operation of drywell o containment sprays for a broad spectrum of acrident sequ 2.
Backup water enhanced by providing independent water and power sources.
blackout sequences.
ld be sources and pumps, hose connection and use of l
ld be explicitly exposures' that could result from manual action
' considered.
WR Owners Group Such provisions development of the Emergency Procedures Guidelines.d assure should minimize the risk of implosion,and hydrogen combus ii
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thattheequipmentwouldbe/preservedinunfloodedcondton.
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bstantial assurance s control provisions should provide ent failure due to hydrogen combusti n is not likely in the 3.
Combustible The that contai severe accident sequences, including # blackout sequences.
periods of cperations while Mark I and II containments are deinerted while more likel at power, particularly during potential preshutdown conditions, should be minimized by reducing the present Technical Specifications permitted value of 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.
Paths for core debris travel should be evaluated for conditions representa-Where the expected path of debris travel 4.
tive of a large scale core melt.
indicates a substantial likelihood of loss of the suppression pool as a release filtering or debris quenching medium in Mark I containments, the torus room under the suppression pool should contain a 3 foot high barrier to trap water and core debris.
Emergency procedures and training should be reviewe 5.
conditions and use plant equipment to best advantage under s be implemented promptly following the staff's review and approval.
conditions.
In addition, improved automatic depressurization system operation for station blackout response (battery backs), and drywell debris barriers in front of suppression pool vents for Mark I containments are highly desirable. The s believes that such barriers are justified if the cost does not greatly exceed about one million dollars.
This proposed generic le'tter has identified areas for im We welcome coments on the which can be implemented at a reasonable cost.
The goal is to proposed actions and other suggestions on the subject ma Sincerely, Robert M. Bernero Director Division of BWR Licensing Office of Nuclear Reactor Regulation
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