ML19344E121
| ML19344E121 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 07/23/1980 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Gary R TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC) |
| References | |
| NUDOCS 8008260659 | |
| Download: ML19344E121 (1) | |
Text
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UNITED STATES
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- 'o, NUCLEAR REGULATORY COMMISSION OO REGloN IV n
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o 611 RYAN PLAZA DRIVE, SUITE 1000 a,
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July 23, 1980 In Reply Refer To:
RIV Dockit Nos.
50-445/IE Circular No. 80-17 50-446/IE Circular No. 80-17 Texas Utilities Generating Company ATTN: Mr. R. J. Gary, Executive Vice President and General Manager 2001 Bryan Tower Dallas, Texas 75201 Gentlemen:
The enclosed IE Circular No. 80-17, is forwarded to you for information.
If there are any questiors related to your understanding of the suggested actions, please contact this office.
Sincerely,
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- Karl V. Seyfdit ~ /
Director
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Enclosures:
1.
IE Circular No. 80-17 2.
List of Recently Issued IE Circulars 8008260 (ff n
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SSINS #6830 Accession No.:
UNITED STATES 8005050065 NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 IE Circular No. 80-17 Date: July 23, 1980 Page i of 2 FUEL PIN DAMAGE DUE TO WATER JET FROM BAFFLE PLATE CORNER Description of Circumstances:
On May 8, 1980, Portland General Electric submitted a Licensee Event Report No. 344/80-06, concerning. the April,1980 discovery of failure of a fuel pin in each of.two assemblies during the past operating cycle.
The LER stated that each of the fuel pins was located adjacent to a joint in the core baffle, and that the failures had resulted from tube vibration resulting from water jet impingement on the fuel pin.
l This general type of damage has been experienced previously.
Three damaged fuel pins were found in 1971-72 at a non-domestic power plant.
Subsequently, one failed pin was found in 1973 and again in 1975 at non-domestic plants.
In 1975, one fuel pin failed at Point Beach. These six fuel pin failures involved bypass flow through gaps in the inside corner of the baffle (the fuel " sees" a 90' angle, i.e., the edge of a box as seen from inside the box).
The baffle joints in these plants had not been peened prior to initial core loading.
Joints were peened following discovery of the failures, and no subsequent damage has been observed near the joints where the above failures were discovered.
More recently, in July 1979 fuel pin damage was detected in ten fuel assemblies at the Swedish Plant, Ringhals Unit 2.
In November, 1979 fuel pin damage was reported at the KO-RI Unit 1 in Korea on two fuel assemblies.
Most recently in April, 1980 fuel pin failures were discovered in two assemblies at the end of Cycle 2 in Trojan.
In all three of the above recent instances, the failures were encountered in assemblies which had been associated with center injection points (the fuel " sees" a 270 angle, i.e.,
the edge of a box as seen from outside the box).
In addition in all three, the core support struc-tures utilized a baffle plate design with a reduced number of edge to edge bolts on adjoining baffles.
An ultimate fix of the baffle joint problem is to peen the entire joint with a
" flat land" peening technique to reduce the gap between baffle segments.
Because of scheduling concerns, this was not accomplished at Trojan during the recent outage.
Instead, PGE decided to install stainless steel pins adjacent to the two baffle joints of concern, and delay further peening efforts until the next refueling outage.
High velocity coolant cross flow (" jetting") through the gaps of the core oaffle joints can result in damage to only a very limited number (usually 1 or
- 2) Juel pins, and only at certain discrete elevations on those pins.
Since
IE Circular No. 80-17 Date: July 23, 1980 Page 2 of 2 there is no mechanism for propagation of the failures to adjacent pins, these failures are not viewed as a significant safety concern.
However, in order to keep fuel failures and resulting primary coolant activity levels as low as possible, we recommend the following actions.
Recommended Actions for PWR Construction Permit Holders and PWR Licensees:
1.
Determine core locations that might be subject to water jet impingement upon fuel pins that could potentially be damaged by fretting.
2.
(Licensees only). Examine fuel pins that were discharged from those locations, or are now at those locations (during the next refueling outage).
3.
Take appropriate actions to correct / prevent occurrence of this problem.
Although this problem has appeared only in certain Westinghouse PWRs, this Circular is being distributed to all PWRs since there may be other designs where the "as installed" core baffle may have plant specific features which could contribute to similar failures.
No written response to this Circular is required.
If you desire additional information regarding this matter, contact the Director of the appropriate i
NRC Regional Office.
IE Circular No. 80-17 July 23, 1980 RECENTLY ISSUED IE CIRCULARS Circular Subject Date Issued To No.
Issued 80-10 Failure to Maintain 4/29/80 All holders of Reactor Environmental Qualifi-Operating Licenses (OLs) cation of. Equipment and Construction Permits (cps) 80-13
' Grid Strap Damage in 5/18/80 All holders of Reactor Westinghouse Fuel Operating Licenses (OLs)
Assemblies and Construction Permits (cps) 80-14 Radioactive Contamination 6/24/80 All holders of Power and of Plant Demineralized Research Reactor Licensees Water System and Resultant (Operating and Construction Internal Contamination of Permits), and Fuel Cycle Personnel licensees 80-15 Loss of Reactor Coolant 6/20/80 All power reactor facilities Pump Cooling and Natural with an Operating License (OL)
Circulation Cooldown or Construction Permit (CP) 80-16 Operational Deficiencies 6/27/80 All power reactor facilities in Rosemount Model 510DU with an Operating License (OL)
Trip Units and Model 1152 or a Construction Permit (CP)
Pressure Transmitters Enclosure