ML19351G222

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Forwards Rept Re Fuel Assembly Heat 64G6XS Holddown Spring Failure Found During Cycle 4 Fueling Outage,Per NRC 810209 Request.Spring Was Replaced Prior to Reinsertion for Third Cycle of Irradiation
ML19351G222
Person / Time
Site: Arkansas Nuclear Entergy icon.png
Issue date: 02/13/1981
From: Trimble D
ARKANSAS POWER & LIGHT CO.
To: Reid R
Office of Nuclear Reactor Regulation
References
1R-0281-06, 1R-281-6, NUDOCS 8102230306
Download: ML19351G222 (2)


Text

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ARKANSAS POWER & LIGHT COMPANY POST OFFICE BOX 551 LITTLE ROCK. ARKANSAS 72203 (501)371-4000 b- February 13, 1981 1R-0281-06 Director of Nuclear Reactor Regulatiot ATTN: Mr. Robert W. Reid, Chief Operating Reactors Branch #4 Division of Licensing U. S. Nuclear Regulatory Comm.

Washington, D.C. 20555

SUBJECT:

Arkansas Nuclear One - Unit 1 Docket No. 50-313 License No. DPR-51 Fuel Assembly Holddown Spring Failure Information (File: 4135, 0510)

Gentlemen:

Your letter dated February 9,1981 requested a report on the fuel assembly nolddown spring failure discovered during the current refueling outage at ANO-1. Attached is a report covering the information requested.

l AP&L will perform a 100% inspection of the ccrc fuel assembly hold-down springs during the next refueling outage and report on the results of the inspection to the NRC.

l Very truiy yours ,

Mt. 74A David C. Trimble Manager, Licensing i

DCT: Y:'ip Attachment l

l 8102230Mdeye,n y,oote sour- uvitir;ss sysTeu

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A REPORT ON ANO-1 BROKEN HOLDDOWN SPRING In the end-of-cycle 4 refaling outage at ANO-1 one fuel assembly out of the 177 examined was found to contain a broken holddown spring.

The broken holddown spring had a single torsional-type through fracture in the top active coil about 30 away from the active / dead coil transition area. The position of the break resulted in the holddown spring maintaining a preloaded condition. The fuel assembly was examined for any evidence of axial motion and none was observed. This fuel assembly is a Batch 5, twice burned assembly.

The failed spring was from Heat 64G6XS, as were all springs used in Batch 5 (56 fuel assemblies). Fifty-seven springs from this heat had_ pre-viously gone through three cycles of irradiation at Oconee-III without failure. An additional 56 springs at Oconee-1 and 50 at Oconee-II from this heat are in their third cycle of operation. Twenty-one springs from this heat have been irradiated for one cycle in TMI-1. No failures have been reported.

The AN0 failure is similar in frequency and visual appearance to the Crystal River-3 spring failure, which hot cell examination showed to be l

fatigue, initiating at a surface anomoly. Because of this similarity to the Crystal River-3 spring, there are no plans to have the AN0 failed spring analyzed for metallurgical condition.

The spring was replaced on the subject fuel assembly prior.to reinsertion for its third cycle of irradiation. The replacement spring, as were all springs in Batch 7, came from a heat that had demonstrated an acceptable grain structure and had undergone a stringent surface examination, both now design requirements. These tighter requirements should reduce or eliminate any future holddown spring failures.