ML20042A706

Requests Waiver from Tech Spec 5.2-1 Re Fuel for Research Reactor.Waiver Permits Use of Fuel Fabricated in Accordance W/Present Day Practices But Not Meeting Tech Specs Written in Early 1970s

ML20042A706
Person / Time
Site:	MIT Nuclear Research Reactor
Issue date:	03/19/1982
From:	Lisa Clark MASSACHUSETTS INSTITUTE OF TECHNOLOGY, CAMBRIDGE
To:	John Miller Office of Nuclear Reactor Regulation
References
NUDOCS 8203230697
Download: ML20042A706 (3)

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MASSACHUSETTS INSTITUTE OF TECHNOLOGY 'hk oM HAktsNG 138 Albany Street Cambridge. Mass. 02139 L CL Ann. Jn D"ector o' rector o' Reac'or operat'oas (617)253 4202 h

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March 19, 1982 4 -

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Mr. James R. Miller, Chief i

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Subject:

Request for Waiver from Technical Specification 5.2-1, License No. R-37, Docket 50-20

Dear Mr. Miller:

Massachusetts Institute of Technology requests a limited and temporary waiver from Technical Specification 5.2-1, applicable to fuel to be used in the MIT Research Reactor, MITR-II.

The purpose of the waiver is to permit use in the near fut.re of fuel that has been fabricate. in accordance with present-day practices but that does not meet the Technical Specifications written in the early 1970's for the MITR-II.

Technical Specification 5.2-1 states that the fuel core shall be

" clad by a layer of aluminum metal 0.015M :Ob b thick". This requires a minimum clad thickness of 0.010". It is requested that a waiver be granted l

l from the tolerances on the nominal 0.015" clad thickness for three elements I

scheduled for use on March 30th.

t Justification for the waiver is the experience that has been gained over the past decade by research and test reactors using uranium aluminide fuel such as that fabricated for the MITR-II. In particular, the U.S. Depart-mentment of Energy's Advanced Test Reactor (ATR) in Idaho has utilized well l

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/ 4 Mr. James R. Miller, Chief Request for Waiver March 19, 1982 page 2 over one thousand elements of this type, made by the same fabricator that produces the MITR fuel. Reference 1 describes ATR experience and states (p. 148) that the release of radioactive fission gas to the primary cooling water appears to be adequately prevented by cladding of uniform thickness

(>0.2 mm, a0.008 in). This corresponds to the minimum nominal cladding permitted for ATR fuel, where the term " uniform" implies a provision for l minor manufacturing deviations (e.g. scratches, indentations, etc.) from the uniform thickness. The ATR fabrication specifications establish 0.008 in.as a minimum criterion, but provide for limited penetration of UA1, particles to a shallower depth. We wish to be able to utilize the same cladding criteria, particularly since irradiation conditions in the MITR are less stringent than those in the ATR, i.e. lower coolant temp-eratures, pressures, and flow rates, 1cwer neutron flux and lower heat flux.

MIT Reactor experience with this type of fuel to date has been favor-able.. Sixty fuel elements have now been used to varying degrees in the MITR-II. Fourteen have attained average burnups of about 40% and have

, been permanently discharged from the reactor upon attaining the limit of 1

1.8x10 fission /cc (less 15% allowed as an uncertainty factor) permitted by Technical Specification 3.11-2e. Cladding failure was experienced in 21 one element at 1.3x10 fission /ce, but was judged to be a manufacturing defect and is believed not to be related to the cladding thickness criteria.

It is our belief that, typically, research reactor technical specifica-tions do not state the tolerances associated with fuel cladding thickness.

Fabrication records indicate that three of the elements scheduled for use in the near future could have a minimum cladding of 0.008" thick, or 0.002" less than allowed by the Technical Specification. Therefore, a waiver from Ref. 1: Beeston, J.M., R.R. Hobbins, G.W. Gibson, and W.F. Francis,

" Development and Irradiation Performance of Uranium Aluminide Fuels in Test Reactors", Nuclear Technology, Vol. 49 p. 136-149 (June 1980) l

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i Mr. James R. Miller, Chief Request for Walver March 19, 1982 page 3 the lower tolerance limit stated in Specification 5.2-1 is requested for these three elements.

There is no significant accident potential arising from adoption of the ATR tolerances on the cladding specification.

i MIT plans to submit an application to the Commission for an amend-ment to Technical Specification 5.2-1 for the above purpose. Meanwhile, however, a waiver is requested so that the fuel may be used at the earliest possible date.

The Standing Subcommittee of the MiT Reactor Safeguards Committee has approved this waiver request.

We shall be happy to furnish any additional information that may be desired.

Sincerely, ble Lincoln Clark, Jr.

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Director of Reactor Operations LC/sbs

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