ML20049H703

Notifies That on 820217 Core Inspection After Pulse Operation Revealed Final Elements 3376-E & 3389-E in-core Lattice Positions F-9 & F-27,respectively,were Cocked.Cause Undetermined.Fuel Elements Returned to Lattice Positions

ML20049H703
Person / Time
Site:	Armed Forces Radiobiology Research Institute
Issue date:	02/24/1982
From:	Tyler P DEFENSE, DEPT. OF, DEFENSE NUCLEAR AGENCY
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
References
000171, 171, NUDOCS 8203030466
Download: ML20049H703 (3)

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ARMED FORCES RADIOBIOLOGY RESE ARCH INSilTUTE B ETH E 5D A, M AR YL AND 20014

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Dear Sir:

This letter is prepared for information only and not as a re'pirtiiig requirement specified in the AFRRI-TRIGA Reactor License (R-84) nor applicable provisions of 10 CFR. The basis for this correspondence was discussed in a telephone conversation between Mr Robert Gallo, USNRC Region I, and Captain Joseph A. Sholtis, Jr. , the AFRRI Reactor Physicist-In-Charge, on 17 February 1982.

I.

Description:

Just prior to and immediately following a $2.85 pulse operation on 17 Feb 1982, the core was visually inspected by a senior reactor operator. The core inspection before the $2.85 pulse on 17 Feb 1982 did not reveal the presence of any cocked fuel elements, however, the core inspection immediately after this pulse indicated that fuel elements

1. 3376-E and #3389-E in core lattice positions F-9 and F-27, respectively, were cocked. In both cases the bottom fixture of each element had been displaced laterally toward the core shroud while the upper handling fixture of each element was canted toward the core center with a portion of the triflute resting beneath the upper grid plate as shown in the attached photo.

II. Corrective action:

Both fuel elements in question were removed, visually inspected, and measured for bow and elongation sequentially in accordance with proper procedures. No visible damage was observed and the fuel measurements indicated no elongation or bow. In fact, in both cases only slight

( 1 8 Mils) increases in the length have occurred over the total 16 year life of these two fuel elements. After verification that no damage had occurred to the subject elements, they were returned to their original lattice positions in the core.

All accessible fuel elements in the F-Ring as well as several elements in the E-Ring were checked for proper seating. As a result of this check, it was found that fuel element #3306-E was additionally cocked in lattice position F-21. This cocked element was not obviously tilted like the others, i.e., it was not clearly observable. Nevertheless, V

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this element was also visually inspected and measured for bow and elongation to verify that no damage had occurred; this proved to be the case.

Therefore, fuel element #3306-E was returned to core lattice position F-21.

III. Discussion:

The AFRRI Reactor Staff began investigating potential contributors to and the incidence of cocked fuel elements at AFRRI in Feb 1978.

An analysis (on file with USNRC) was performed to determine if the fueled regions of adjacent elements could come into contact for a variety of cocked fuel element configurations. The results show that fuel meat section contact cannot occur.

On 18 February 1982, the AFRRI reactor was pulsed eight times with step reactivity insertions ranging from $1.21 to $2.85 and no instances of cocked fuel elements were observed.

Although cocked fuel elements pose no adverse health and safety consequences and there has never been any damage associated with their occurrence at AFRRI (there does not appear to be any credible potential for system damage), they do cause inconvenience to the operations staff and a temporary delay in operations. Therefore AFRRI is interested in their cause and in reducing or eliminating their recurrence.

N0h PAUL E. TYLER Captain, MC, USN Director a

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