ML20128D788

Application for Amend to License R-106,revising TS 5.2.b to Allow Reactor Operation W/Full Flip Fueled Cores Consisting of Less than 80 Flip Fuel Elements While Maintaining Desired Control Over Mixed Cores

ML20128D788
Person / Time
Site:	Oregon State University
Issue date:	02/01/1993
From:	Andrea Johnson Oregon State University, CORVALLIS, OR
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20128D794	List: ML20128D788 ML20128D807
References
NUDOCS 9302100228
Download: ML20128D788 (2)

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! OREGON SnTE UNIVERSITY I

Radiation Center A100 Corvallis, Oregon 97331 5903 Telephone 503 737 2M1 Fax 503 737 0480 il 5

February 1,1993 3-U. S. Nuclear Regulatory Commission -

Document Control Desk

Washington, D. C. 20555 l

Reference:

Oregon State University TRIGA Reactor (OSTR),

l Dacket No. 50 243, License No. R 106

Subject:

Request for Amendment to OSTR Technical Specification 5.2.b Gentlemen:

As part of the preparation for converting the OSTR from high-enriched uranium (HEU) fuel to low 3nriched uranium (LEU) fuel,it is necessary to find the minimum ~ number of . ~

FLIP fuel elements required to run the reector at 1 MW.; This is estimated to require a core i . excess reactivity of about $'3.00 which should be achieved with about 76 FLIP elements.

j in order to confirm the core loading required for a core excess of about $3.00, a revision 2'

to Technical Specification 5.2.b is required.

This specification states 'in part that "Any operational core assembly involving FLIP p fuel shall have no less than 80 Flip fuel elements, located in a contiguous, central region _."'

[ The original p trpose of this specification, as stated in the basis for 5.2.b, and as detailed

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in Technical Specification 3.4, is to limit flux peaking in mixed cores. _ Howeveriit appears L that specification 5.2.b was not concisely worded, and thus it applies not only to mixed f cores but also to cores which consist entirely of FLIP fuel.

Although we believe the broad coverage.of Technical Specification 5.2.b was not

-intended, even if this specification was designed to apply to full FLlP fueled cores there are

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clearly no power density problems associated with full FLIP core assemblies consisting cf '

less than 80 FLlP fusi elements. Evidence of this is provided in the data contained in.

- Amendment No. 4 to the OSTR Safety ~ Analysis Report (SAR). Referring to Tables 3.6 and -- .

3.7, the SAR states at the bottom of page'12 that "The full FLIP cores have lower maximum power densities than mixed cores.-- As more FLIP fuelis added, the maximum

! power per element and the ratio of P ,/Ps, decrease'." The worst case coreshnalyzed were mixed assemblies with only 35 FLIP elements surroundsd by 24_ standard elements.

These had a calculated FLIP fuel power density of Just over 24 kW/ element, which is still

~s ign_ificantly below the 32 kW/ element generated in the Torrey Pines TRIGA reactor.

' However, the worst case small core is not practically feasible because-the initial OSTR :

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criticality required a total of 65 FLIP fuel elements.' Therefore,it is concluded'that a full V

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U.S. Nuclear Regulatory Commission Page 2 February 1,1993 FLIP core consisting of between 65 and 85 fuel elements would have a maximum average power density significantly below 24 kW/elemant, and slightly higher than the 16 kW/ ele-ment calculated for the 85 FLIP element cores. Thus, the maximum power density is still well below that of safely operated reactor cores and well below the maximum safety limit for FLIP fuel.

Therefore, we would like to request that Technical Specification 5.2.b be changed to read (italics indicate change):

"b. The TRIGA core assembly may consist of standard fuel elements, FLIP fuel elements, er a combination thereof (mixed core). Any operational mixed core assembly shall have no less than 80 FLIP fuel elements, located in a contiguous, central region."

This change will allow reactor operation with full FLIP fuelcd cores which consist of

!ess than 80 FLIP fuel elements, while still maintaining the desired control over mixed cores. The proposed change has been reviewed and approved by the OSTR Reactor Operations Committee. In addition, proposed revised pages for the Technical Specifica-tions are attached for your convenience. Should there be a need for further clarification, or should more information be required, please let me know. Thank you for ycur consideration of this request.

Yours sincerely, A. G. oh 'on Director agj\ddWc\techspec.52b cc: Non-Power Reactor, Decommissioning, and Environmental Projects Dircctorate, USNRC, Washington, D. C. 20555 ATTN: Mr. Al Adams Regional Administrator, USNRC, Region V, Walnut Creek, CA USNRC, Region V, ATTN: L. Norderhaug USNRC, Region V, ATTN: Phil Qualls Oregon Department of Energy, Salem, Oregon ATTN: Mr. D. Stewart-Smith Prof. S. E. Binney, Chairman, Reactor Oparations Committee Prof. B. Dodd, Reactor Administrator Prof. J. F. Higginbotham, Senior Health Physicist T. V. Anderson, Reactor Supervisor -

A. D. Hall, Reactor Operator i

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