05000344/LER-1982-006, Forwards LER 82-006/01T-0.Detailed Event Analysis Encl

Forwards LER 82-006/01T-0.Detailed Event Analysis Encl

ML20052G444
Person / Time
Site:	Trojan File:Portland General Electric icon.png
Issue date:	05/06/1982
From:	Steele R, Yundt C PORTLAND GENERAL ELECTRIC CO.
To:	Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
Shared Package
ML20052G445	List: 05000344/LER-1982-006, Forwards LER 82-006/01T-0.Detailed Event Analysis Encl 05000344/LER-1982-006-01, /01T-0:on 820426,17 Fuel Assemblies Found to Have Abnormal Clad Degradation.Caused by Water Jet Impingement & Induced Vibration on Fuel Rods.Fuel Assemblies Modified Using Stainless Steel Pins
References
CPY-379-82, IEIN-82-27, TAC-48402, NUDOCS 8205180364
Download: ML20052G444 (4)

LER-1982-006, Forwards LER 82-006/01T-0.Detailed Event Analysis Encl

Event date:
Report date:
3441982006R00 - NRC Website

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s Portland General Electric Company May 6, 1982 Trojan Nuclear Plant CPY-379-82 P.O. Box 439 Rainier, Oregon 97048 (503)556-3713 w

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Mr. R, H. Engelken g

Regional Administrator i

US Nuclear Regulatory Commission

.:i-Creekside Oaks Office Park 1450 Maria Lane - Suite 260 Walnut Creek, California 94596-5368

Dear Sir:

In accordance with the Trojan Plant Operating License, Appendix A, USNRC Technical Specifications 6.9.1.8.c, attached is Licensee Event Report No.

82-06 concerning a situation where abnormal degradation was discovered in the fuel cladding. A total of 17 damaged fuel assemblies were discovered during a preplanned fuel inspection program. An immediate report has already been made regarding this event (letter CPY-368-82 to R. H. Engelken dated April 26, 1982).

Sincerely, C. f ndt

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Gen al Manager S[

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MtL CPY/GJK:ga Attachments c:

LER Distribution File 93.24a(Q) g20 51 Sc% 4 yq t

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REPORTABLE OCCURRENCE 1.

Report No:

82-06 2.

Report Date:

May 6, 1982 3.

Occurrence Date:

April 26, 1982 4.

Facility: Trojan Nuclear Plant, PO Box 439, Rainier, Oregon 97048 5.

Identification of Occurrence:

Abnormal degradation was discovered in 17 fuel assemblies loaded in Trojan Cycle 4 core during a preplanned fuel inspection program while refueling.

6.

Conditions Prior to Occurrence:

The plant was shut down for refueling in Mode 6.

The core was in the process of being unloaded into the spent fuel pool.

7.

Description of Occurrence:

During a preplanned fuel inspection program to locate suspected leaking fuel assemblies, 17 assemblies were found to have degraded fuel cladding.

Severe damage to some perimeter fuel rods was found in 8 Region F fuel assemblies by visual inspection. Portions of rodlets were missing and loose fuel pellets were found.

In addition, 9 other nonobvious damaged fuel failures were found through fuel sipping. A total of 11 Regicn F assemblies, 4 Region E assemblies, and 2 Region D assemblies were found damaged and will not be used in the subsequent cycle. All assemblies being returned to the core for Cycle 5 ha/e been sipped to ensure fuel assembly integrity.

8.

Designation of Apparent Cause of Occurrence:

The apparent cause of the fuel damage is water-jetting induced vibration of fuel pins in fuel assemblies that are adjacent to baffle plate joint locations with enlarged gaps (see attached figure). Two types of baffle gap related failures were present. The first type is the outside corner or conter injection jetting failure identical to the 1980 fuel damage.

In this case the water jet impinges directly on the third rod from the corner and causes it to fail in the lower axial regions from direct water impingement combined with induced rod whirling / vibration. There were 3 fuel assemblies that failed by this mechanism since the peening corrective action in 1981. Less damage occurred in these 3 assemblies than occurred in 1980 indicating that peening was partially successful but did not correct the problem. The second type of baffle gap related failure is the inside corner or corner injection jetting failure whereby a jet of water flows parallel to the fuel bundle perimeter face between the fuel and the baffle plate. The flow causes fuel rod whirling to occur at the first few rod locations and leads to severe rod failure.

It appears dhat the jetting problem for these types of joints was caused by the 1981 poening on the outside corner joints.

(See attached diagram for exact location of fuel assembly failures occurring on baffle plate locations.)

Reportable Occurrence May 6, 1982 Page Two 9.

Significance of Occurrence:

This event had no effect on plant or public safety.

The plant is designed to operated with 1% failed fuel which corresponds to 3.735 pC/gm dose equivalent iodine-131. During operation specific activity of the pr imary coolant reached a nominal value of 85% of the Standard Technical Specification limit paragraph 3.4.8 which allows a maximum of 1.0 pCi/ gram dose equivalent iodine-131.

10.

Corrective Action

An augmented fuel inspection program was conducted. All fuel assemblies that are to be used in the subsequent cycle were leak checked by fuel sipping and visually inspected to be damage free. Accessible loose pellets and debris will be retrieved from dhe reactor vessel internals and refueling cavity. Damaged assemblies adjacent to the baffle will be replaced with new modified fuel assemblies using stainless steel pins and/or other devices (eg, clips) to ensure fuel integrity.

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