ML20064N351

Responds to Ltr Re Conversion of Gtrr from High to Low Enriched U Fuel.Answers to Questions Listed

ML20064N351
Person / Time
Site:	Neely Research Reactor, 05000276
Issue date:	03/21/1994
From:	Karam R Neely Research Reactor, ATLANTA, GA
To:	Mendonca M Office of Nuclear Reactor Regulation
Shared Package
ML20064N355	List: ML20064N351 ML20064N358
References
NUDOCS 9403290271
Download: ML20064N351 (6)

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~ March 21, 1994-Mr. Marvin M. Mendonca, Senior Project Manager Non-Power Reactors and Decommissioning Project Directorate Division of Operating Reactor Support Office of Nuclear Reactor' Regulation U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 l

Dear Mr. Mendonca:

This is in . response to your letter dated March 3, 1994, concerning the conversion.of the GTRR from High-to Low-enriched uranium fuel. The answers to the questions follow. The answer to Question #1'is answered by-me. The answers to the other Questions were provided by-Dr. Woodruff of ANL.

Question #1:

L In reference to letter of January 21, 1993, Attachment'2, Section 2.b., <

A. Described the bases for the 760 gallons per minute (GPM).

limit. Explain how the orifice limits minimum flow in the core to 760 GPM. Describe how this and'other flow rates are used in the analyses and how these flow rates are ensured.

B. In order to ensure that the information used in the -)

analysis is in docketed material, reference "la" should '

bet i.

Letter, R. A. Karam to Director, Office of Nuclear Reactor Regulation, U.S. Nuclear Regulatory Commission, -

January 21, 1993, Attachment 1 " Analyses for Conversion of the Georgia Tech ' Research Reactor from HEU' to LEU Fuel," J. M. Matos,-S.C. Mo, and W. L Woodruff, Argonne National Lab., September 1992.

Answer 2

'A. The GTRR has two primary coolant pumps: one is a 1800 GPM pump that is used in Mode 2 operation (> one MW) and gg another pump rated at 1000 GPM that is used in Mode ~1' 9403290271 DR 940321 y - 'I p ADDCK 05000160 W L Tew 542507 GTmocAATL . PDR j ru 404.es3-932s (venty 404 894 390o)

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4 Mr. Marvin M. Mendonca March 21, 1994 Page 2 operation (1 one MW). The analysis that was made in 1967,in~ the original SAR, arbitrarily constrained the flow to 760 GPM as a conservative measure. It was found' that even at a flow of 760 GPM, no departure from nucleate boiling would occur until the power reached 5.5 MW.(Figure II-1-Technical Specifications).

The flow trip set point for Mode 1 operation is 1000 GPM. The flow trip set point for Mode 2 operation is 1625 GPM. Normal flow rates obtained from the two pumps are 1800 GPM and 1100 GPM respectively.

B. Reference "la" has been changed to read as recommended.

The Answers to Ouestions 2, 3. and 4 Our response to questions 2, 3 and 4 are contained in a letter from Dr. William L. Woodruff to me. This letter is appended-as Attachment 1.

Should you have additional questions, please let me know.

Sincerely, QD, f-}- hkk R.A. Karam, Ph.D., Director Neely Nuclear Research Center RAK/ccg Enclosures-2 1

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' O Argonne National Laboratory J1 TECHNOLOGY DEVELOPMENT DtV.

9700 South Cass Avenue, B207 Argonne,IL 60439-4841 March 11,1994 Dr. Ratib A. Karam, Director Neely Nuclear Research Center Georgia Institute of Technology Atlanta, GA 30332

Dear Ratib,

We are assuming thatyou can address Item 1 and thus will address only Items 2 - 4 of the NRC's request for additional information (FAX ofMarch 3,1994 letter from the NRC with attachment).

In Item 2A, lx>th numbers are correct. The number from page 6 in NUREG-1313 is for silicide fuel with a volume fraction of 0.45, while the LEU fuel specified for the GTRR has a volume frac-tion of only 0.31. A figure is enclosed from Appendix A of NUREG-1313 that shows that at 31%

the thermal conductivity is about 100 W/mK (a more conservative number of 90 W/mK was used I to allow for uncertainties). In Item 2B, the clading material is not pure Al but rather a 6061 alloy whose conductivity is about 180 W/mK (104 Blu/hr-fbF). j in item 3, the range of meat dimensions quoted in the table represents the tolerances in the spec- l ification for fabrication of the fuel. For the neutronics analysis an average value has been used.

In the safety analyses of the hot channel these uncertainties are assumed to be included in the engineering uncertainty factors introduced (see Attachment 2 of the ANL report Engineering Uncertainty Factors).

For item 4, I amjust enclosing copies of one page from ANic6675 and a plot from the JANUS analysis for the Weatherhead DNB correlation and two pages from IAEA-TECDOC-233 for the Whittle and Forgan flow instability correlation. These both cover the range of operating condi-tions in the GTRR. The main reason for using the Weatherhead correlation was to maintain con.  !

sistency with earlier analyses of the GTRR . These data are taken from the references listed in the ANL report. By the way I spotted a typo in reference 24 of that report it has ANL-6674, and j this should be ANL-6675 as shown above and in the enclosure. j l

I hope this information will be sufTicientforyour response to the NRC. If there are still questions

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please let me know what more can be done.  ;

k U. S. Department of Energy University of Chicago

g-4 i Sincerely, William L. Woodruff, RERTH Program enclosure: documentation ec: J. E. Matos, J. L. Snelgrove, A. Travelli i

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Page 2

8 NUREG-1313 Safety Evaluation Report related to the Evaluation of Low-Enriched Uranium Silicide-Alumin'um Dispersion Fuel for Use in Non-Power Reactors U.S. Nuclear Regulatory Commission Office of Nuclear Reactor Regulation July 1988

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- NUREG-1313 16 Appendix A 'I