ML19323J344
| ML19323J344 | |
| Person / Time | |
|---|---|
| Site: | Maine Yankee |
| Issue date: | 05/28/1980 |
| From: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Groce R Maine Yankee |
| References | |
| NUDOCS 8006200043 | |
| Download: ML19323J344 (1) | |
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UNITED STATES
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KING OF PRUSStA, PENNSYLVANIA 19406 May 28, 1980 Docket No. 50-309 Maine Yankee Atomic Power Company ATTN:
Mr. Robert H. Groce Senior Engineer - Licensing 25 Research Drive Westborough, Massachusetts 01581 Gentlemen:
The enclosed IE Circular No. 80-13, " Grid Strap Damage in Westinghouse Fuel Assemblies," is forwarded to you for information.
No written response is required.
If you desire addition 1 information regarding this matter, please contact this office.
Sincerely, l
f?
i Boyce H. Grier Director
Enclosures:
1.
IE Circular No. 80-13 with Attachment 2.
List of Recently Issued IE Circulars CONTACT:
D. L. Caphton (215-337-5262) cc w/encis:
E. Wood, Plant Superintendent E. W. Thurlow, President THIS DOCUMENT CONTAINS 8006200643,
POOR QUALITY PAGES
ENCLOSURE 1 SSINS No.: 6830 Accessions No.:
UNITED STATES 7910250495 NUCLEAR REGULATORY COMMISSION f [fd OFFICE OF INSPECTION AND ENFORCEMENT I D
WASHINGTON, D.C. 20555 uo ou Jl IE Circular No. 80-13 Date:
May 28, 1980 Page 1 of 2
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GRID STRAP DAMAGE IN WESTINGHOUSE FUEL ASSEMBLIES Description of Circumstances:
During the refueling operation at Salem Unit 1, it was noted by the licensee that some of the assemblies that were removed had suffered grid strap mechanical damage.
This was reported to the NRC in LER 79-44.
Subsequent to this discovery all fuel assemblies were removed from the core for examination.
The degree of the damage to the grid straps was classified in three categories: small pieces missing (15 assemblies), grid material ripped and laid over (5 assemblies),
larger sections missing and fuel pins exposed (11 assecblies).
No damage to the fuel pins was observed.
A total of 31 assemblies suffered some grid damage.
The damage appeared to be the result of corner to corner interaction of the grid straps of diagonally adjacent fuel assemblies during the vertical loading
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and unloading movements.
No correlation of the damage to core location, grid strap elevation, or manufacturing and shipping batches has been identified.
The licensee and the fuel manufacturer established the following guidelines for reloading damaged assemblies: (1) those assemblies with full width pieces missing will not be reloaded for cycle 2, (2) those assemblies with deformed edges and those with small pieces missing will be reloaded with special pro-cedures to prevent furthe.r damage.
Salem Unit 1 is fueled with 17X17 Westinghouse assemblies.
Similar grid problems have occurred at other facilities fueled with 14X14 and 15X15 Westing-house assemblies; however, fewer assemblies were damaged in those instances.
Recommended Actions:
All licensees using 14X14, 15X15, or 17X17 Westinghouse assemblies are advised to:
(1) Visually inspect grid straps of those fuel assemblies which are discharged from the core as well as those assemblies which are moved to the spent fuel pool for control rod replacement and are subsequently returned to the core.
i
IE Circular No. 80-13 Date:
May 28, 1980 Page 2 of 2 (2) Review the fuel handling precautions recommended by Westinghouse at a meeting on May 25, 1979, with NRC and the licensee for Salem (Attachment 1). Adopt those recommendations which are pertinent.
No written response to this Circular is required.
If you required additional information regardin NRC Regional Office.g these matters, contact the Director of the appropriate
Attachment:
Summary of Meeting Notice dated 5/30/79 y
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Attachment to IE Circular No. 80-13
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UNITED STATES E9 NUCLEAR REGULATORY COMMISSION WASHINGTON D. C. 20555 C
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Docket No. 50-272 LICENSEE:
PUBLIC SERVICE ELECTRIC & GAS COMPANY (PSE&G)
FACILITY:
SALEM UNIT NO. 1
SUBJECT:
SUMMARY
OF MEETING HELD ON MAY 25, 1979. TO DISCUSS DAMAGE OBSERVED TO FUEL GRID ASSEMBLIES DURING THE SALEM UNIT NO. 1 REFUELING OUTAGE On May 25, 1979, we met with representatives of Public Service Electric &
Gas Company (PSE&G) and Westinghouse to discuss the cause and extent of damage observed to the Salera Unit No.1 fuel grid assemblies during the current refueling outage for cycle 2.
A list of attendees is-enclosed.
Significant discussions are sumarized below.
The licenses anii Westinghouse provided a detailed discussion of the da:. age observed to the Salem fuel grid assemblies during the cycle 2 refueling outage which comenced in April 1979.
Due to the Indications
. observed during the initial stages of the outage, the decision was made
- to unload all fuel hssemblies from the core.
Of the fuel assemblies (193) inspected, 28 assemblies were detemined to have varying degrees of danage to one or more of the eight grid assemblies per fuel assembly, The grid asse-blies provide lateral support to the fuel rods.
In no i
l case was dacage observed to the fuel rods themselves. The grid assembly dar. age observed, which was generally located at the corners of the grid assemblies, was categorized as follows:
Ca aaory Type of Damace No. of Grid Assemblies 1
small pieces missing 15 2
grid' material ripped 4
and laid over 3
larger sections missing and 9
fuel pins exposed 1
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Attachment to IE Circular No. 80-13
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Meeting Sumary for Salem Unit 1 -
Of the above, fuel assemblies with categories 1 and 2 damage were detennined by the licensee to be acceptable-for use and will be reloaded for cycle 2! as a precautionary measure assemblies with category 3 damage i
will not be reloaded.
The basis for this detemination was that assemblies with category 1 and 2 damage can be used without any loss of function of i
the damaged grids.
Fuel assemblies Qith category 3 damage, however, no longer fully restrain all fuel rods in the manner provided for in the design. Their reuse should be based on further analysis.
Of the data collected and the reload films reviewed, no pattern has been established for the observed damage.
Also, it has not been determined whether the damage occurred during fuel insertion for cycle 1, or during removal or readjustments for cycle 2, or both.
It is believed that corner-to-cornsr interaction may have occurred between grid assemblies of adjacent fuel asse:blies especially when diagonal fuel assocblies have been renoved and scme degree of lateral movement is possible.
Under these conditions the grid assernblies may have been aligned such that the corners interacted during vertical movement.
Of the pieces missing (about 61), a total area of about 25in2 is involved.
These pieces range from about.3in2 up to about 5.5in2 Approximately 12in2 of material has been recovered from' the core or the fuel asse:rblies during the unloading of the core.
In addition, the core was inspected with a TV camera.
With regard to the potential for flow blockage from the missing material, Westinghouse indicated that if all the peices originally missing were to be located such as to partially block the inlet nozzle area of the one fuel assembl, analyses similar to that described in Section 3.4 of the Salem FSAR indicate that no problem would exist.
The smaller pieces still missing are expected to easily pass up through the fuel asse:ablies during operation and not present any problems to the control rod drive mechanisms.
The largest that any of the missing pieces could be, based on the base areas on grid assemblies, is slightly greater than 2in2 Westinghouse has reco:::nende~d additional fuel assembly handling precautions Ao minimize the potential for corner-to-corner interaction between grid assemblies.
Included among these recomendations are,1) a revised Icading sequence which would load fuel assemblies 'froa the sides of the
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core toward the center, 2) a slight offset in position as corner fuel assemblies are lowered into the core until they are about 10" above the base plate and then making a lateral adjustment into final position,
- 3) the conditionally accepted assemlies in categories 1 and 2 would be leaded in a special sequence to minimize relative motion with adjacent i
i assecblies, 4) those assemblies in category 2 would be loaded against the H
- r. ore baffle, where possible and 5) revised load cell limits on the mani-i pulator crane in an attemp: :o more easily detect increased loads i
during fuel handling.
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Attachment to I'E Circular No. 80-13
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Meeting Sumary for Salem Unit 1 -
Westinghouse acknowledged and sumarized similar grid assembly problems that have occurred at other facilities.
Although these other oc.currences did not involve as many fuel assemblies as in this Salem situation, similar damage has been observed to 14x14,15x15 and 17x17 fuel assemblies.
In some instances the fuel was removed, and in others, the fuel was re-loaded with no known adverse effects.
With regard to the Salem Unit 1 refueling analysis, the licensee indicated praliminarily, that the core parameters are expected to be essentially unchanged due to the revised core loading that will result.
The licensee agreed to address the potential effects that the unaccounted for pieces of grid material might have on the core thermal hydraulic analysis and on control rod operation.
This information will be included prior to restart of Salem 1 in a supplement to the licensee's reload application for cycle 2.
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0 Gary G. Zech, Project Manager Operating Reactors Branch #1 Division of Operating Reactors
Enclosure:
List of Attendees cc:
w/ enclosure
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See next page 6
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I ENCLOSURE 2 IE Circular No. 80-13 Date:
May 28, 1980 Page 1 of 1 RECENTLY ISSUED IE CIRCULARS Circular Subject First Date Issued To No.
of Issue 80-03 Protection from Toxic 3/6/80 All Power Reactor Facil-Gas Hazards ities with an (Operating License (OL),
80-04 Securing Threaded lack-3/14/80 All Power Reactor Facil-ing Devices on Safety-ities with an OL or CP Related Equipment 80-05 Emergency Diesel Gen-4/1/80 All Power Reactor Facil-erator Lubricating Oil ities with an OL or CP Addition and Onsite Supply 80-06 Control and Account-4/14/80 Medical Licensees in ability Systems for Categories G and G1 Implant Therapy Sources 80-07 Problems with HPCI 4/3/80 All Power Reactor Facil-Turbine Oil System ities with an OL or CP 80-08 BWR Technical Speci-4/18/80 All General Electric fication Inconsis-BWRs holding a power tency - RPS Response reactor OL Time 80-09 Problems with Plant 4/28/80 All holders of Internal Communi-a reactor OL cations Systems or CP 80-10 Failure to Maintain 4/29/80 All Power Reactor Environmental Facilities with an Qualification of OL or CP Equipment 80-11 Emergency Diesel 5/13/80 All Power Reactor Generator Lutie Oil Facilities with an Cooler Failures OL or CP 80-12 Valve-Shaft-To-Actu-5/14/80 All Power Reactor Faci-ator Key May Fall Out of lities with an OL or CP Place h en Mounted Below Horizontal Axis