ML111950379

University of California, Irvine - *Redacted* Licensee Response to NRC Request for Additional Information Dated May 26, 2010 and Transmittal Letter of Thermal-Hydraulic Analysis and Nuclear Analysis for Uci Triga Reactor

ML111950379
Person / Time
Site:	University of California - Irvine
Issue date:	06/07/2011
From:	Geoffrey Miller University of California - Irvine
To:	Dimeglio A, Linh Tran Document Control Desk, Office of Nuclear Reactor Regulation
Lynch, Steven - NRR/DPR/PRPB, 415-1524
Shared Package
ML120050026	List: ML111950379 ML111950380 ML111950452
References
TAC ME1579
Download: ML111950379 (7)

Text

University of California - Irvine (UCI)

License No. R-116 Docket No. 05000326 Response to NRC Request for Additional Information (RAI)

Dated May 26, 2010 Redacted Version*

Security-Related Information Removed

• Redacted text and figures blacked out or denoted by brackets

UNIVERSITY OF CALIFORNIA, IRVINE BERKELEY

• DAVIS - IRVINE - LOS ANGELES

• RIVERSIDE - SAN DIEGO - SAN FRANCISCO SANTA BARBARA - SANTA CRUZ George E. Miller IRVINE, CA 92697-2025 Senior Lecturer Emeritus (949) 824-6649 or 824-6082 Department of Chemistry and FAX: (949) 824-8571 Director,Nuclear Reactor Facility email : gemiller@uci.edu FacultyAdvisor for Science, UC/ Centerfor EducationPartnerships June 7, 201 I US Nuclear Regulatory Commission Document Control Desk Washington DC 20555 Attention: Linh Tran, SenioIr Project Manager Francis DiMeglio, Senior Project Manager Re: Docket 50-326 Relicense, RAI dated May 2 6 th 2010, TAC ME1579

Dear Ms Tran,

Mr DiMeglio:

Please find attached the final response regarding remaining items from the earliest RAI that were formlerly transmitted to you in draft form. Included are copies of two reports from b.contractor. THESE CONTAIN MATERIAL OF A SENSITIVE NATURE ND SHOULD BE PROTECTED from public disclosure.

I declare under penalty o perjury that the foregoing and the attached are true and correct to my knowle dge.

Executed on June 7, 2011 Dr. George E. Miller Au0

University of California, Irvine Reactor License R-116, Docket 50-326 Response to NRC Request for Additional Information (RAI) dated May 2 6 th 2010 (TAC NO. ME1579)

DatedFebruary28th2011.

Pleasenote that any references to Technical Specifications apply only to PROPOSED TechnicalSpecifications (not yet implemented), a complete copy of which is attachedto this response (may be separatelytransmitted).

Response to three issues raised were deferredpending contractwork to analyze the core.

This response addressesRAI issues3, 5, and 7 (e). A previous response datedMay 2 6 th 2010 dealt with the other R4I issues.

3. NUREG-1 537 states, a thermal hydraulic analysis should be performed for the reactor.

Inyour response dated January 27, 2010 to NRCs request for additional information (RAI) dated December 3, 2009, the analysis is provided through a reference for analyses made at two research reactors. However, the information is incomplete in that no information is provided on thelsimilarity of the research reactors involved.

Please provide a comparison between the thermal hydraulic parameters (i.e., channel dimensions and geometry, linear power, etc.) and characteristics of the UCINRF core vs.

the referenced research reactors core so as to provide validity to using this information for the UCINRF.

A contractbetween DOE ald General Atomic has recently been completed in this regard.

A copy of the full report GA 911201 will be providedfor information. This will be incorporatedinto the faciliýy SAR.

As anticipatedand demonstratedthrough prioroperationsover many years without incident,this core design provides adequate heat removalfor the standardTRIGA fuel employed During either steady state operations,peak power dissipationand temperatureswill remain considerably lower than those that have been routinely experiencedsafely with thisfuel type elsewhere. Analyses were performedusingRELAP5 code up to 300kw (20% above licensedpower). Convection cooling using available channels between elements is clearly more than adequate to maintainfuel temperatures well below any safety limits and avoid any near approachto DNB conditions.

Key parametersdetermined are containedin Table 2-1 which is reproducedbelow.

UCI RAI response 2/28/11 page 1

DESIGN DATA Number of Fuel Rods Fuel Type UZrHx Uranium Enrichment, % 19.79 Zirconium Rod Outer Diameter, mm Fuel Meat Outer Diameter, mm Fuel Meat Length, mm Clad Thickness, mm Clad Material THERMAL-HYDRAULI, REACTOR PARAMETERS Reactor Steady State Operation, kW 250 Limited Safety System Setting, kW 275 Number of fuel elements Diameter, mm (in.)

Length (heated), mm (in.)

Core total flow area, mm 2 (ft2) 36,362 (0.3914)

Core total wetted perirr eter, mm (ft.) 9416 (30.89)

Flow channel hydraulic diameter, mm (ft.) 15.45 (0.05068)

Core total heat transfer surface, m 2 (ft2) 3.587 (38.61)

"Radial" peaking factor~ (rpf)

Axial peaking factor (apf) 1.446 1.352 Hot rod factor (rpf x ap.f) 1.955 Inlet coolant temperature, 'C (OF) 25. (77)

Coolant saturation temperature, °C (°F) 114. (237)

Peak fuel temperature in average fuel element, °C ("F)' 214 (418)

Maximum wall temperature in hottest element, °C (OF) 123 (254)

Peak fuel temperature in hottest fuel element, °C (OF)' 253 (488)

Core average fuel temperature, °C (OF) 1 164 (327)

Minimum DNB ratio at 0.275 MW 7.27 Minimum DNB ratio at 0.30 MW 6.67 1 The thermal-hydraulic parameters shown are for the reactor assumed operating at 300 kW.

UCI RAI response 2/28/11 page 2

5. NUREG 1537, Part 1, Section 4.5, Nuclear Design, states the applicant should discuss normal operating conditions, reactor core physics parameters and operating limits. The discussion should include a discussion of the complete, operable core; control rod worths; kinetic parameters; excess reactivities; shut down margins; and flux distribution for all planned configurations for the life of the core.

Section 4.5 of the 1999 SAR presents a representation of the flux distribution in the core.

However, based on 1999 SAR Figure 4-13, this flux plot in 1999 SAR Figure 4-16.

appears to not be representative in that it shows no flux peaking in the center flux trap and does not portray the flux near the position of the adjustable transient rod (which is important to the Limiting Safety System Setting (LSSS)). Please provide appropriate flux distribution information including how the distribution will affect the peak to average power ratio.

In response to this request, a contract with GeneralAtomic was placed andfulfilled to provide a computer modeling of the UCI reactorcore utilizing MCNPX code. This report, GA 91196, will be p rovidedfor information and incorporatedinto the facility SAR. As anticipated,as a result of burn-up and the addition offuel elements over time, the reportrevises calculatedvalues of some of the core parametersproposedat the time of initial construction. However none of the revisions affects the conclusions as to the continuedsafety of operationsfor thisfacility with its current core andfuel designs. Key parametersdetermined are summarized in Table 2-1 of that report which is reproduced below. Again, the parameteIrsshow that the fuel is operatingwell below any design considerationsfor peakpower concerns, and which are demonstrateddaily to be safe at higherpower TRIGA facilities using similar, and even higherfuel density,fuels.

The calculatedcore designipredictsnegative temperatureand void coefficients, as well as a decreasingmoderator!effectiveness with coolant temperature increases.

UCI RAI response 2/28/11 page 3

DESIGN DATA Number of Fuel Rods Fuel Type UZrH Uranium Enrichment, % 19.79 Zirconium Rod Outer Diameter, mm Fuel Meat Outer Diameter, mm Fuel Meat Length, mm Clad Thickness, mm Clad MaterialI REACTOR PARAMETERS Reactor Steady State dperation, kW 250 Cold Clean Excess Reactivity, Ak/k( 2.82 Measured Cold Clean Excess Reactivity, Ak/kp ($) 2.66 Prompt Fuel Temperatui re Coefficient of Reactivity (BOL), Ak/k-°C, 23-1000oC (x 1 04) -0.70 to -1.11 Coolant Void Coefficient, Ak/k-% void, 0 - 10%,

(x 104) -7.40 to -3.68 Moderator Coefficient, Ak/k -°C, 23-10000 C, (x 10"4) 0.884 to 0.396 Maximum Rod Power at 250 kW, kW/element 4.519 Average Rod Power at 250 kW, kW/element 3.125 Prompt Neutron Lifetime, psec 98.5 Effective Delayed Neu ron Fraction 0.0079 ARI cold, clean core, Ak/kl3 ($) -5.88 Shutdown Margin, Ak/k13 ($) (with most reactive rod out) -2.03 Additional Shutdown case, Ak/kp ($) (with most reactive rod out and next most 'reactive rod stuck 50% out) -1.27 In respect to specificity of the fluxes at various locations,presumably the concerns relate to the fuel temperaturesthat might be attained This is best shown in the thermal report where the maximum power peaking values (>1.40) are shown in Figure 2-3 reproduced below. These occur at only 5 locations;B2, B4, C5, C6, and C7. The present location of the InstrumentedFuel Element (IFE)at B4 is calculatedto be at an ideal locationfor assessing actualfuel temperature reached Technical specification revisions will recognize the conclusions of the analysis in specifying locationsfor the IFE.

It must be emphasized however, that analyses andpractice with similar core andfuel design continue to confirm that operationswith thisfuel type at UCI are well below safety limits and below actual operationallevels at otherfacilities.

UCI RAI response 2/28/11 page 4

7. NUREG 1537, Part 1, Chapter 14, Technical Specifications, states the applicant needs to establish Technical Specifications that will provide reasonable assurance that the facility will function as analyzed in the SAR without endangering the environment or the health and safety of the public and the facility staff.

e) Proposed TS 3.1.5 Fuel Burnup. This statement described why there is no limitation on fuel burnup and is not a TS. Propose appropriate TS wording or justify why a TS is not needed.

While there is no clear casefor establishinga limit on burn upfor 8.5% by weight, stainless steel clad, 20% enriched TRIGA fuel,this issue has been revisitedwith the contractor.

The contractorhas directedour attention to NUREG 1282 (1987) which addressedthe issue of high uranium contentfor TRIGA fuels. In that study the resultsfrom experiments with variousformulations of TRIGA fuel (zirconium hydride alloys) were analyzed. In addition to demonstratingthat increasinguranium content from 8.5 wt% up to 45 wt%

had little effect, the higher uranium contentfuels were irradiatedin ORR to over 50%

burn-up. In this processfuel swelling and growth, rod bowing, hydrogen migration, and fission product releasefraction were measured. Only small percentagechanges were observed. Thusfor 8.5 %fuel (andothersO the contractorfeels confident in stating that fuel burn-up to 50% of uranium content is an acceptablegoalfor TRIGA fuel. This will be incorporatedas a Tech Spec limitationfor the UCI reactor.

UCI RAI response 2/28/11 page 5