ML20245A463

Forwards Supporting Info Re 890313 Request for Exemption from Criticality Monitoring Requirements of 10CFR70.24.Addl Info Covers Refs,Calculational Assumptions & Results Which Led to Exemption Requests for Hot Cell 1

ML20245A463
Person / Time
Site:	07000824
Issue date:	04/10/1989
From:	Christopher Boyd BABCOCK & WILCOX CO.
To:	Rouse L NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS)
References
25426, NUDOCS 8904250211
Download: ML20245A463 (5)

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Babcock & Wilcsx nurontstancs tasonarony a McDermott company P.o. Box 11165 Lynchburg, VA 245061165 I

(804) 522-6000

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Attn:

Leland C. Rouse, Chief Fuel Cycle Safety Branch ww I'"

Divistor. of Industrial & Medical Nuclear Safety Washington, DC 20555

Reference:

Letter from C. C. Boyd to L. C. Rouse, dated March 13, 1989.

Gentlemen

• The Babcock & Wilcox Company, Naval Nuclear. Fuel Division Research Laboratory (NNFD-RL), is providing the requested information to supple-ment our referenced request for an exemption from the criticality monitoring requirements of 10 CFR 70.24.

This additional information will show the references, calculational assumptions, and results which lead to our exemption request for our No.1 Hot Cell.

If you should have any further questions, please contact me at (804) 522-5753.

Very truly yours, BABC0CK & WILC0X NNFD Research Laboratory G

g Charlie C. Boyd, Jr.

License Administrator jhc Attachments I \\

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g C-25426 (4.dN

V The following information will provide the calculational assumptions, and results which lead to our initial request for an exemption from the criticality monitoring requirements of 10 CFR 70.24 (letter from C. C. Boyd to L. C. Rouse, dated March 13, 1989).

A listing of the references used during the evaluation of Hot Cell No.

I and in the following discussion is provided as Attachment 3.

The event used by NNFD-RL for our calculations of dose (shown in ) is based on a burst of IE18 fissions. The requirements for our criticality monitoring system were 'oased on 10 CFR 70.24 which requires that a monitoring systua must be able to respond to an excursion causing a dose of 20 Rads accumulating within 60 seconds at an unshielded distance of 2 meters.

Using Appendix B of Reference 2, we determined that a gamma sensitive detector located outside of Hot Cell No. I would not respond to the minimum excursion as required by the regulations.

Using standard gamma attenuation techaiques in conjunction with XSDRN calculations to determine neutron attenuation, we determined that a 1E18 fission burst would result in a gamma plus neutron dose outside the cell of only 0.006 Rem. The gamma attenuation calculation used a prompt gamma fission spectrum from Reference 5. is a table showing the maximum direct radiation dose (gamma and neutron) from an initial fissions burst occurring in Hot Cell No.1.

With such a low dose rate, 0.006 Rem, the monitors would not detect a criticality if one were to occur.

Also, a total dose of 0.006 Rem does not pose a significant hazard to anyone who would be working next to the cell.

Therefore, based on the information presented above, NNFD-RL submitted the 10 CFR 70.24 exemption request.

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Attachment ' 2 3

MAXIMUM DIRECT RADIATION DOSE FROM INITIAL BURST OF IE18 FISSIONS IN HOT CELL NO. 1 Gamma Dose Neutron Dose Total Dose Distance.

Unshielded Shielded Unshielded Shielded Shielded Feet Rem Rem.

Rem Rem Rem 10' 2237 0.003 7416 0.003 0.006 20 554 0.001

~1824 0.001 0.002 25 352.

0.001~

1159 0.000 0.001' 30 243 0.000 798 0.000 0.000 40 136 0.000 442

-0.000 0.000 50 86 0.000 278 0.000' O.000

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LIST OF REFERENCES Reference-1

." Criticality Accident Alarm. Systems," U.S. NRC _ Regu-latory Guide 8.12 Revision 1, dated January,1981.

Reference 2 "Criticali ty Accident Alarm Sy stems," ANSI /ANS-8.3, 1979.

Reference.3

" Assumptions Used For. Evaluating the Potential Conse-quences of Accidental Nuclear Criticality in a Uranium Fuel - Fabrication Plant, U.S.

NRC Regulatory Guide 3.34 Revision 1, dated July,.1979.

Reference 4

" Radiological Contingency Plan -(RCP), Naval Nuclear Fuel-Division ' Research Laboratory,"' License SNM-778, dated June, 1987.

Reference 5

" Reactor Shielding Design Manual," by leodore Rockwell,

. III, dated 1956.

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