ML19320C745

Forwards Questions Re Fuel Assembly Holddown Spring Failures First Observed at Davis-Besse 1 & Under Investigation by B&W.Results of Holddown Spring Insps at Facility as Well as Safety Significance Required within 60 Days

ML19320C745
Person / Time
Site:	Rancho Seco
Issue date:	07/01/1980
From:	Novak T Office of Nuclear Reactor Regulation
To:	Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT
References
NUDOCS 8007170667
Download: ML19320C745 (6)

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UNITED STATES o$

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NUCLEAR REGULATORY COMMISSION k.*....,o l 3

WASHINGTON. D. C. 20565 f

July 1,1980 Docket No. 50-312 Mr. J. J. Mattimoe Assistant General Manager and Chief Engineer Sacramento Municipal Utility District 6201 S Street P. O. Box 15830 Sacramento, California 95813

Dear Mr. Mattimoe:

Recently we nave been notified by the Toledo Edison Comany that a number of fuel assembly holddown spring failures have been observed at the Davis-Besse, Unit No.1 plant which is currently undergoing its first refueling outage. We understand that as a result of these failures, Babcock & Wilcox has requested that you conduct examinations of fuel assemblies at your facility to determine if any failures have occ trred. We are interested in knowing the results of holddown spring inspections at your facility as well as the safety significance of operating with broken springs in the core.

Enclosed is a set of questions regarding this subject.

It is requested that you provide responses to these questions within 60 days of receipt of this let:cr.

Sincerely,

& ' ZY-Thomas M. Novak, Assistant Director for Operating Reactors Division of Licensing

Enclosure:

Holddown Spring Questions cc'/ enclosure:

See next page 4 AD-OR:CL

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O Eacramento Municipal Utility District ccw/ enclosure (s):

Christopher Ellison, Esq.

David S. Kaplan, Secretary and Dian Grueuich, Eso.

General Counsel California Energy 'Comission 5201 S Street lill Howe Avenue Sacramento, California 95825 P. O. Box 15820 Sacramento, California 95813 Ms. Eleanor Schwartz Sacramento County California State Office Board of Supervisors 600 Pennsylvania Avenue, S.E., Rm.,ol c

827 7th Stre'et, Room 424 Washington, D.C.

20003 Sacramento, California 95814 Docketing and Service Section Office of the Secretary Businass and Municipal Department U. S. Nuclear Regulatory Comission Sacramento City-County Library Washington, D.C.

20555 828 I Street Sacramento, California 95514 Resident Inspector Director, Technical Assassment kg,.

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alifornia 95628 Divisica Office of Radiation Programs Dr. Richard F. Cole (AW-459)

Atomic Safety and Licensing Board U. S. Environmental Protection Agency Panel Crystal Mall #2 U. S. Nuclear Regulatory Comic:'on Arlington, Virginia 20460 Washingten, D.C.

20555 U. S. Environmental Protection Agency Mr. Pederick J. Shen Region IX Office Atomic Safety and Licensing Board ATTN:

EIS CCORDINATOR Parel 215 Frement Street U. S. Nuclear Regulatory Commission San Fra cisco, California 94111 Washington, D.C.

20555 Mr. Robert B. Borsum Elizabeth S. Bowers, Esq.

Sabcock & Wilcox Chairman, Atomic Safety and

.fuelear Fovier Generation Division Licensing Board Panel suite 120, 7735 Old Georgetown Road U. S. Nuclear Regulatory Commission uthesda, Maryland 20014 Washington, DC 20555 Thomas Baxter, Esq.

Shaw, Pittran, Potts & Trowbridge 1800 M Street,"tM clashington, D. C. -20036 -

Herbert H. Brown, Esq.

Mr. Michael R. Eaton Lawrence Coe Lanpher, Esq.

Energy Issues Coordinator Hill, Christopher and Phillips, P. C.

Sierra Club Legislative Office i

1900 M St., NW 1107 9th St., Room 1020 Washington, D. C.

20036 Sacramento, CA 95814 Helen Hubbard P. O. Box 63 Sunol, California 94586 1

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Sacramento Municipal Utility District cc w/ enclosure (s):

Atcmic Safety and Licensing Board Panel U. S. Nuclear Regulatory Commission

!ashington, D.C.

20555 Atomic Safety and Licensing A'ppeal Board Panel U. S. Nuclear Regulatory Commission Washingten, D.C.

20555 California Department of Health ATTN: Chief, Environmental Radiation Control Unit Radiological Health Section 714 P Street, Room 4g8 Sacrsmento, California t

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o Enc 1csure HOLD-DOWN SPRING QUESTIONS TO LICENSEES 1

(If the reactor is down for refueling and the reactor vessel head is off) Examine all fuel assembly holddown springs in the core and in the shent fuel pool and report the number and extent"of damage on the springs and affected assembly components.

or (Alt.) (If the reactor is operating.) Review video tapes of the core from the.last refueling and examine all assemblies in the spent fuel pools.

Report the number and extent of damage on the springs and affected assembly components.

2.

Provide a discussion of the safety significance of operating with one or more broken springs in the core. Your discussion should include, but not necessarily be limited to the following:

Assume the holddown spring is broken, provide an estimate nf the(Provide a.

flow conditions under which the assemblies would be levitated.

the value of the force required to lift the assently, the flow conditions under which that force would be supplied, the number of coolant pumps that would be in operation under such conditions, and the schedule of reactor operations under which such conditions might have been achieved.) Contrarily, demonstrate the margin between the assembly weignt and the calculated maximum applied lift-off force, if there is such margin, b.

Have any loose assetubly parts (i.e., broken springs, pieces of cladding) been observed anywhere in the primary system? Describe your methods for loose part detection. Are there installed noise detectors capable of detection of broken springs, pieces of cladding, or vibrating assembliesi c.

Have there been any excore or in-core neutron detector indicatwT of levitated assemblies? Describe the expected reactivity effects that would result from lift-off or reseating of assemblies with broken hold-down springs. What efforts are being utilized to detect locse assemblies by either nuclear or mechanical monitoring devices?

d.

Have there been any observed indications of lateral repositioning of loose assemblies?. Describe the methods used to detect lateral assembly motion.

Describe the degree of lateral repositioning that is physically (dimensionally) possible after lift-off. What a:e the postulated worst-case effects of a laterally displaced assembly?

e.

(i) Describe the degree of "wont-case" mechanical damage that would be expected as a result of movement of a " loose" assembly (one with a broken spring; against adjacent assemblies, core baffle, or other core components.

'(ii) Discuss the results of flow tests or other experiments that have provided measurements of axial or lateral vibratory motion of an assembly after lift-off or that would otherwise support the response to Q 2.e(i).

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3.

Provide a hescription of the cause of the failures and corrective action i

to reduce the likelihood of future failures at your facility.

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