ML091470390

University of Wisconsin, Madison, Response to Request for Clarification Regarding Heu/Leu Conversion for License Amendment No. 17

ML091470390
Person / Time
Site:	University of Wisconsin
Issue date:	05/01/2009
From:	Agasie R Univ of Wisconsin - Madison
To:	William Schuster Office of Nuclear Reactor Regulation
References
RSC 1008, TAC MD9592
Download: ML091470390 (4)

Text

UNIVERSITY OF WISCONSIN NUCLEAR REACTOR LICENSE NO. R-74 DOCKET NO. 50-156 RESPONSE TO REQUEST FOR CLARIFICATION REGARDING HEU/LEU CONVERSION REDACTED VERSION SECURITY-RELATED INFORMATION REMOVED REDACTED TEXT AND FIGURES BLACKED OUT OR DENOTED BY BRACKETS

1 Nuciear Reactor Laboratory UWNR University of Wisconsin-Madison 1513 University Avenue, Room 1215 ME, Madison, WI 53706-1687, Tel: (608) 262-3392,.. FAX: (608) 262-8590 email: reactor@engr.wisc.edu, http://reactor.engr.wisc.edu May 1, 2009 RSC 1008 Mr. William Schuster Project Engineer, Research and Test Reactors United.States Nuclear Regulatory Commission Washington, D.C. 20555

Subject:

Docket 50-156, License. R-74 Response to Request for Clarification for Amendment No. 17 to Facility License No. R-74 University of Wisconsin Nuclear Reactor TAC No. MD9592

Dear Mr. Schuster:

By telephone conference, on April 301 2009, you requested clarifying information to our April 10, 2009 response to the Commission's request for additional information, dated February 26, 2009. Specifically, you requested clarification to the responses to questions 52 and.55.

the calculated drain time of to the In' question 52 we. indicate represents the time to drain during a postulated reduction in cooling accident, which is analyzed in section 13.3 of our safety analysis report (SAR), submitted to the Commission on August 25, I

2008. In question 55 we supplied the analysis that demonstrates a complete loss of coolant accident (LOCA) is more limiting than

a partial LOCA.

The analyses in. section 13.3 of the SAR and in response to question 55 may not be bounding since the air cooled transients begin at  ; however, using the assumptions in section 13.3.1 of the SAR, it would only takes to drain to This reduction in time before the air cooled transients begin results in a 5.6% higher initial decay heat power of 19.6kW,. as compared to the assumed power of 18.6kW and therefore, slightly higher rod temperatures.

However the drain time calculated in section 13.3.1 is based on nominal dimensions of the reactor pool and beam ports. Using

as-built measurements for the reactor pool surface area, accounting for beam port tube wall thickness and the actual low reactor pool water level SCRAM set point, a more accurate drain time can be calculated using equation 13.3.1 from the SAR as follows:

td = -AA0 -[ [l- ] Equation 13.3.1 where:

td- Time to drain pool from the low reactor pool water level SCRAM set point to-a height of , in seconds.

g Acceleration due to gravity given as 32.174 ft/s 2 .

AP Actual area of pool surface-measured as A0 = True open area of beam port tube is .

NOTE: Section 13.3.1 of the SAR incorrectly reports the nominal dimension of the beam port tube, of 0.5ft, as the inside diameter.

Cd Discharge coefficient assumed to be 0.6.

h, = Height of water from the low reactor pool water level SCRAM set point to determined to be 3 h = Height of water from the to determined to be The actual drain time to from an assumed sheared open beam port accident would be , which is greater than the assumed drain time of . As a result, the decay heat at is 18.5kW and the analyses of section 13.3.3 of the SAR and question 55 are bounding.

It should be noted however, that the analyses of SAR section 13.3.3 and question 55 neglect several mitigating-measures that minimize the occurrence and consequence of this type of

accident. Specifically, it is assumed the reactor has operated continuously for 50 days," but the facility is not staffed for round-the-clock operations. Additionally, the beam ports are filled with beam stop plugs when no experiment is inserted and the beam port can not be opened during reactor operations due to hazardous radiation levels. To limit the release of Ar-41 to the environment, administratively, beam ports can not be opened any earlier than 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> following reactor operations. When experiments are inserted into the reactor beam port thiy must incorporate a flanged end that seals the experiment in the beam port and provide an air tight and water tight seal. Finally, the beam port incorporates.a lead shutter internal to the biological shield, that is normally~closed, and could easily reduce the flow out of a postulated sheared open beam port.

Therefore, true drain time from a damaged beam port would be' considerably longer and actual decay heat much lower than assumed in the foregoing analyses.

If you should have any further questions, please do not hesitate to contact me.

Reactor Director