ML17193B240
| ML17193B240 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 03/23/1981 |
| From: | Goddard R NRC OFFICE OF THE EXECUTIVE LEGAL DIRECTOR (OELD) |
| To: | Little L, Remick F, Wolf J Atomic Safety and Licensing Board Panel |
| Shared Package | |
| ML17193B241 | List: |
| References | |
| NUDOCS 8103250014 | |
| Download: ML17193B240 (6) | |
Text
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OFFICE~ OEL John F. ~~lf, Esq., Chairman 3409 Shepherd Street Chevy Chase, Maryland 20015
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Dr. Linda W. Little ~
5000 Hermitage Drive Raleigh, N~rth Carolina 27612 Dr. Forrest J. Remick 305 E. Hamilton A~enue State College, PA 16801 In the Ma*tter of COMMONWE6LTH EDISON. COMPANY (Dresden Station its 2 and 3)
Docket No~/.. _0-237 and 50-249 (Spent Fuer-t'O odification)
Dear Licensing Board Members and Parties:
Enclosed is th~ NRC Staff's supplemental testimony on spent fuel assembly channel bowing, by Horace K. Shaw.
The Staff is awaiting word from the Licensing Board regarding Board Question 2 *and the testimony, if any, sought by the ~oard t~ereon, as was discussed in the conference call held on March :13, 1981.
. ~ : ~~\\'..'.
cc: Philip P. Steptoe, Esq.
(iary N. Wright Mary Jo M~rray, Esq.
Atomic Safety and Licensing Board Panel Atomic Safety a_nd Licensing Appeal :poard Panel Docketing~*and Service Section Respectfully submitted, Richard J. Goddard Counsel for NRC Staff NRC Cen tra 1 OELD FF (2)
Shapar/Engelhardt Olmstead/Karman Christenbury/Scinto RJGoddard/chron (2)
CABarth P0 1Connor, 314 Phil.*
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DATE~
NRC FORM 318 1101801 NRCM 0240 OFFICIAL RECORD *copy
,-, USGPO: 1980-329*824
UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION In the Matter of COMMONWEALTH EDISON COMPANY Docket Nos. 50-237 and 50-249 (Spent Fuel Pool Modification)
(Dresden Station, Units 2 and 3)
- SUPPLEMENTAL TESTIMONY OF HORACE K. SHAW ON FUEL CHANNEL BOWING I am employed as a Senior Mechanical Engineer, Division of Licensing, Office of Nuclear Reactor Regulation, United States Nuclear Regulatory Commission.
A statement of my professional qualifications is attached to this testimony.
Introduction The purpose of this testimony is to present the results of the NRC review of Applicant's testimony concerning potential interference resulting between surfaces where certain fuel assemblies with large total deformations (bulge plus bow), which are to be stored in certain minimal-size storage locations within the proposed Dresden spent fuel racks.
Description The Dresden Nuclear Power Plant Units 2 and 3 have proposed a spent fuel rack modification to accomplish high density spent fuel storage.
New racks will b~ of 9xll-and 9xl3-array configuration and will be fabricated by spacing stainless steel tubes at specific pitches. Because of the tolerances permitted in the fabrication process, dimensional deviations in the pitch would develop; some storage locations will be smaller than others.
S.10825 o 0 7..:Z Spent fuel assemblies are deformed.
During normal *reactor operation, neutron flux tends to produce bowing of the fuel channel box and pressure differential across channel walls induced by core coolant flow tends to produce bulge
-deformation in fuel channels.
Concern has thus been raised as to the possible interference between the deformed fuel assembly channel box and the storage rack walls that may develop during insertion or withdrawal of a deformed fuel assembly into or from a minimal-size storage location.
Two possible inter-ferences have been identified.
The first possible interf~rence may develop between the wall of the fuel channel in mid-span where the total (bulge and bow) deformation is at a maximum, and that of the storage location. The second possible interference may exist at the top of a minimal size storage location where the lead-in clip further reduces the size of the opening.
Our evaluation will assume the worst combination of dimensional interferences.
Discussion The Commonwealth Edison Company has measured the inside dimensions of some storage location openings.
Measurements taken from four 9xll array racks currently stored in the Dresden facility indicated that only one storage rack location measures less than 5.74".
The measured dimension is 5.729" with an accuracy of+/-. 0.01".
Efforts were also made to measure 1736 channel sides.
The total (bulge and bow) deformation found was not more than 0.15" and 0.2" respectively for 86% and 94.5% of all the channel sides measured.
Only 15
- sides have total deformations greater than 0.3".
The greatest total deformation reading was found to be 0.43" (once) and the next greatest reading was found to be 0.39" (once).
With the conservative assumption that the centrally situated channel with the greatest total deformation is in the smallest storage location, max bum interferences of 0.25" may exist at the mid-span of the channel, and 0 -y. )II may exist at the lead-in clips.
Forces required to overcome dra~
caused by these interferences were estimated conservatively to be 310 lbs.
and 200 lbs., respectively.
Fuel assemblies are inserted into storage locations by their own weights.
Since each fuel assembly weighs 680 lbs. and will produce about 600 lbs.
gravitational force even when it is fully submerged in water, there should be no other force required to insert the worst deformed fuel assembly into the smallest storage location.
No extraordinary loadings will be experienced by the load handling system.
To withdraw this fuel assembly from the storage location, however, the handling system must produce forces to overcome the gravitational force caused by the weight of the fuel assembly as well as the drag force caused by the inter-ferences.
The maximum force is thus estimated to be 1190 lbs. This is well within the capability of the handling system.
Analyses also indicated that stress level caused by this loading is below design for all components in the handling system.
The structural integrity of the storage racks and fuel assemblies were also checked and found to be within the design cap?bilities.
Drag forces will be proportionally greater if actual interferences should be greater than the assumed figures.
However, assuming the total deformation is 0.50" instead of 0.43" drag force will increase to 409 lbs. instead of 310 lbs.
Even this unlikely deformation will not change the analytical results substantially.
The Dresden facility currently is or shortly will be imple-menting the following procedures:
- a.
Channel boxes manufactured using a new heat treatment and fabrication process resulting in more dimensional stability for these channels will be used.
- b.
A screening process which will eliminate channels with large total deformation from further service.
- c. *An operating procedure which describes actions to be taken in case a fuel assembly is stuck in a storage location.
Con cl us ion Based on the above evaluation, it is the conclusion of the NRC staff that the concern raised regarding interference developed between walls of fuel assemblies and storage locations within the proposed Dresden spent fuel racks does not represent a safety problem.
HORACE K. SHA\\.J Professional Experiences:
Senior Mechanical Engineer, USNRC, 1974-present Specialist-Research, Member of Technical Staff, Atomics International Div., Rockwell International Corp., 1965-1974 Consultant, Private Practice, 1964-1965 Project Engineer, Johnson and Johnson, 1955-1964 Design Engineer, Koppers Company, 1952-1955 Research Fellow, University of Washington, 1949-1950 Plant Engineer, Chinese Petroleum Corp., 1945-1948 Staff Engineer, Tzu-Yu Iron and Steel Works, 1943-1945 Educational Background National Central University, China, BSME, 1943 University of Washington, Seattle, MSME, 1950 Registered Professional Engineer in Illinois