ML103300040

Response to Request for Additional Information for License Renewal to Facility License No. R-74 University of Wisconsin Nuclear Reactor

ML103300040
Person / Time
Site:	University of Wisconsin
Issue date:	11/22/2010
From:	Agasie R Univ of Wisconsin - Madison
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
TAC ME1585
Download: ML103300040 (3)

Text

tNuclear 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 November 22, 2010 RSC 1070 United States Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555

Subject:

Docket 50-156, License R-74 Response to Request for Additional Information for License Renewal to Facility License No. R-74 University Of Wisconsin Nuclear Reactor TAC No. ME1585 (Technical RAI)

Dear Sirs:

By letter, dated October 26, 2010, the Commission has requested additional information in order to complete the review for the University of Wisconsin Nuclear Reactor's (UWNR) request to renew facility license number R-74.

Enclosed are the responses to the request for additional information. The responses are provided in the same order as the Commission's requests. The format of the enclosure is to restate the request followed by the response. The original request is counter shaded to aid in the separation between request and response.

I certify under penalty of perjury that the foregoing is true and correct.

Since y Executed on: Z e/*

Robert J. gaise Reactor Director Enclosure L'Wýz

UWNR Response to NRC Request for Additional Information NRC RAI:

PrpsdTS321 'Operable Control Rods,'allows operation with ~a rninidmurni of three .

control elements with scramn capability:ý However, the ev'aluation in the Safety An~alysis eportfoof thighenriche uranium to low enriched uranium fuel shows that pin: power and peaking factors~ (arid tihe resulting thermall hydraulic

,calculation~s)were6etermiedk*withethe controlblades banked. Please provide ananalysis thatshows tatt reactor operation isacceptable w control .......... by proposed TS 3 2,1.

Licensee's Response:

It is the facility's intention to operate the reactor at full power with all five control elements operable and banked to ensure uniform fuel burn up. However, it is conceivable that operations may be necessary with the regulating blade and one control element with scram capability out of service due to equipment failure or maintenance, especially since the facility does not possess any spare control element drive components.

The MCNP model from the LEU Conversion SAR was used to calculate maximum pin powers that would result from having the regulating blade and one control element with scram capability out of.service. Placing the out of service control elements in their most extreme positions of either fully inserted or fully withdrawn are bounding since any intermediate position would bring the out of service control element closer to the bank thereby flattening the flux gradient.

The table below indicates the 1.0MW bank height of the remaining three control elements and the resulting maximum pin power at licensed full power. The table also indicates the maximum pin power in the event of a reactor power excursion up to the Limiting Safety System Setting of proposed TS 2.2.2 plus 2% uncertainty, or 1.3MW.

As shown in section 4.7.7 of the LEU Conversion SAR, table 4.7.12, page 111, the design basis maximum pin power is 29.04kW which corresponds to a MDNBR of 1.818 (Groneveld 2006) and 1.211 (Bernath) as shown in table 4.7.13, page 114. As can be seen in the table below the design basis maximum pin power, and therefore the resulting thermal-hydraulic analysis, bounds all conditions with the regulating blade and one control element with scram capability out of service.

It must be noted that the resulting change in pin power peaking factors may preclude currently acceptable physical positions for the location of the IFE as indicated in figure 4.7.39 on page 109 of the LEU Cbnversion SAR. However, proposed TS 2.2.1, requires the IFE to be placed in locations with a pin power peaking factor between 0.87 and 1.16 for a limiting safety system setting (LSSS) of 4000 C or a peaking factor at least 1.16 for a LSSS of 500'C. The model has identified what locations are acceptable but the resulting core maps have not been included for the sake of brevity.

Control Remaining Maximum Pin Maximum Pin Elements Out of Service Elements Power at Power at Out of Service Position Bank Height 1MW 1.3MW

[inches] [kW] [kW]

T-rod rBd Full IN Full IN 14.00 17.09 22.22 Reg. Blade Full IN T-rod Full IN1301722.4 Reg. Blade Full OUT 1.0 72 24 T-rod Full OUT 11.00 21.82 28.37 Reg. Blade Full IN T-rod Full OUT Reg. Blade Full OUT 10.50 21.91 28.48 Blade 1 Re.BaeFlFull IN N16.00 21.50 27.95 Blade 1 Full IN 15.00 21.16 27.51 Reg. Blade Full OUT Blade 1 Full OUT 11.50 18.93 24.61 Reg. Blade Full IN Blade 1 Full OUT 11.00 18.68 24.28 Reg. Blade Full OUT Blade 2 Full IN Reg. Blade Full IN 16.00 21.84 28.39 Blade 2 Full OUT Blade2 FullOUT 11.50 18.85 24.51 Reg. Blade Full IN Blade 2 FullIOUT 11.00 18.60 24.18 Reg. Blade Full OUT Blade 3 Full IN Reg. Blade Full IN 16.00 21.38 27.79 Blade 3 Full IN Reg. Blade Blade Full OUT 3 Full OUT 11.00 18.82 24.47 Reg. Blade Full IN Blade 3 Full OUT Reg. Blade Full OUT 1 1 2