ML090990541

University of Florida Training Reactor, Submittal of Startup Report Based on Issuance of Order Modifying License No. R-56 to Convert from High-To-Low-Enriched Uranium Fuel (Amendment No. 26)

ML090990541
Person / Time
Site:	05000083
Issue date:	04/06/2009
From:	Haghighat A Univ of Florida
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML090990541 (9)

Text

UNIVERSITY of UFI LORIDA College of Engineering 202 Nuclear Sciences Bldg.

Department of Nuclear & Radiological Engineering PO Box 118300 Gainesville, FL 32611-8300 352-392-1401 x306 352-392-3380 Fax haghighat@ufl.edu April 6, 2009 Document Control Desk U.S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Rockville, MD 20852-2738

SUBJECT:

STARTUP REPORT BASED ON ISSUANCE OF ORDER MODIFYING LICENSE NO. R-56 TO CONVERT FROM HIGH - TO LOW - ENRICHED URANIUM FUEL (AMENDMENT NO. 26) - UNIVERSITY OF FLORIDA TRAINING REACTOR Please find enclosed the Startup Report for University of Florida Training Reactor, Docket No. 50-83. This report is being submitted as required by issuance of order modifying License R-56 dated September 1, 2006. If you have questions on the content of this report, please contact Dr. Alireza Haghighat, Interim Director of the University of Florida training Reactor, at 352-392-1401.

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

Executed on April 6, 2009.

Si Alireza Haghighat, PhD Professor and Chair of the NRE Department Interim Director of UFTR Cc Mr. Alexander Adams Jr., Senior Project Manager, NRC Mr. Duane Hardesty, Project Manager, NRC Mr. Johnny Eads, Branch Chief, NRC Mr. Thomas Blount, Deputy Director, NRC Mr. John Donahue, Inspector, NRC Mr. Craig Bassett, Inspector, NRC Mr. Brian Shea, Reactor Manager, UF Dr. Ce Yi, Research Scientist, UF Dr. Glenn Sjoden, RSRS Committee Chair The Foundationfor The Gator Nation An Equal Opportunity Institution

UFTR Operation Report with the New LEU fuel Prepared by:

Dr. Ce Yi Dr. Alireza Haghighat Brian Shea University of Florida Training Reactor Nuclear & Radiological Engineering Department University of Florida Gainesville, Florida 32608 Submitted to:

Mr. Alexander Adams Jr., Senior Project Manager Mr. Duane Hardesty, Project Manager U.S. Nuclear Regulatory Commission Office of Nuclear Reactor Regulations Mail Stop: O-12D3 Washington, DC 20555-0001 (April 6, 2009)

Title 10 of the Code of Federal Regulations (10 CFR) Section 50.64 requires licensees of research and test reactors to convert from the use of high-enriched uranium (HEU) fuel to low-enriched uranium (LEU) fuel, unless specially exempted. The University of Florida Training Reactor (UFTR) completed the fuel conversion in August 2006. NRC requested an outline of the reactor startup report after the fuel conversion, which should include the following information:

1. Critical Mass Measurement with HEU Measurement with LEU Comparisons with calculations for LEU and if available, HEU

2. Excess (operational) reactivity Measurement with HEU Measurement with LEU Comparisons with calculations for LEU and if available, HEU

3. Regulating and Safety control rod calibrations Measurement of HEU and LEU rod worths and comparisons with calculations for LEU and if available, HEU

4. Reactor power calibration Methods and measurements that ensure operation within the license limit and comparison between HEU and LEU nuclear instrumentation set points, detector positions and detector output.

5. Shutdown margin Measurement with HEU Measurement With LEU Comparisons with calculations for LEU and if available, HEU

6. Partial fuel element worths for LEU Measurements of the worth of the partial loaded fuel elements

7. Thermal neutron flux distributions Measurements of the core and measured experimental facilities (to the extent available) with HEU and LEU and comparisons with calculations for LEU and if available, HEU.

8. Reactor physics measurements Results of determination of LEU effective delayed neutron fraction, temperature 2

coefficient, and void coefficient to the extent that measurements are possible and comparison with calculations and available HEU core measurements.

9. Initial LEU core loading Measurements made during initial loading of the LEU fuel, presenting subcritical multiplication measurements, predictions of multiplication for next fuel additions, and prediction and verification of final criticality conditions.

10. Primary coolant measurements Results of any primary coolant water sample measurements for fission product activity taken during the first 30 days of LEU operation.

11. Discussion of results Discussion of the comparison of the various results including an explanation of any significant differences that could affect normal operation and accident analyses.

These above items are discussed as follows:

1. Critical Mass Table I compares U-235 and total uranium mass for the LEU and HEU cores.

Table 1. Uranium mass in the LEU and HEU cores Type of fuel U-235 mass (g) Total uranium mass (g)

HEU core (fresh core, calculated) 3422.00 3679.57 LEU (fresh core, calculated) 3850.00 19,493.67 LEU (fresh core, measured) 3841.88 19,504.06

• Measured data are from fuel manufacturer (Ref. 1)

The nominal U-235 mass per fuel plate is 14.5 g for HEU, and 12.5 g for LEU fuel. The total mass of U-235 for the fresh core is calculated by multiplying U-235 mass per plate and number of fuel plates loaded in the core. The total uranium mass for fresh core can be estimated using U-235 mass divided by the fuel enrichment (H4EU: 93.00%; LEU:

19.75%). The HEU core had 21 full bundles (11 plates per bundle) plus a partial bundle with 5 plates, while, currently, the LEU core has 22 full bundles (14 plates per bundle).

Details of comparison between LEU and HEU fuel can be found in Table 4-1 of the UFTR fuel conversion SAR.

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2. Excess (operational) reactivity Table 2 compares the measured and calculated excess reactivity for the LEU and HEU cores.

Table 2. Calculated and measured excess reactivity Excess reactivity HEU (depleted) LEU (fresh)

Calculated (Ak/k %) 0.470 1.013 Measured (Ak/k %) 0.380 1.015 For details of the calculations results, see Table 4-12 in the fuel conversion SAR and Ref. 2

3. Regulating and Safety control rod calibrations Table 3 compares the blades worth for both measurement and calculations of LEU and HEU core.

Table 3. Comparison of Control Blades Worth for the HEU and LEU cores Control HEU HEU LEU-fresh LEU Blade (calculated) (measured) (calculated)* (measured)

(Ref. 2)

Regulating 0.87% 0.82% 0.93% 0.76%

Safety 1 1.35% 1.21% 1.45% 1.40%

Safety 2 1.63% 1.36% 2.04% 1.73%

Safety 3 2.03% 1.88% 2.11% 1.95%

• Calculated with 22 fuel bundles and two dummy bundles and B-10 concentration of 0.12ppm; estimated based on averaging all-in and all-out approaches.

4. Reactor power calibration The Nuclear Instrumentation (NI) systems remain unchanged after the fuel conversion.

The NI and power calibration procedures during the First Power Run include:

0 I Wto verify proper instrumentation response, and expected critical position.

0 100 W to verify proper instrumentation response.

0 1 kW to verify proper instrumentation response, and conduct partial restricted area radiological survey to verify shielding effectiveness.

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• 10 kWto verify proper instrumentation response, and conduct partial restricted area radiological survey to verify shielding effectiveness.

& 90 kWto verify proper instrumentation response, and conduct partial restricted area radiological survey to verify shielding effectiveness; perform heat balance calculation to verify NI performance (conservative at < 100 kW)

• 100 kW to verify proper instrumentation response, and conduct partial restricted area radiological survey to verify shielding effectiveness; complete SOP A-2 Surveillance (multiple runs)

UFTR full power rate for both LEU and HEU core is 100 kW. The reactor power trip point is lowered to 119 kW (LEU) from 125 kW (HEU).

5. Shutdown margin Table 4 compares shutdown margins for both LEU and HEU cores. Note that shutdown margin is conservatively calculated and measured with the most reactive control blade (Safety 3) fully withdrawn.

Table 4. Shutdown Margins for the Current HEU Core and the Reference LEU Core Depleted HEU Core HEU Core Reference LEU Core LEU core (calculated) (measured) (Calculated) (measured)

Shutdown Margin 3.110 3.010 2.900 2.875 (Ak %)

6. Partial fuel element worths for LEU Individual fuel bundle worth is not measured. However, during initial loading of the LEU core, detector responses for different number of fuel bundle are recorded (See Section 9).

The calculated power contribution from each fuel bundle in both the fresh LEU core and HEU depleted core is listed in Table 4-11 of the fuel conversion SAR.

7. Thermal neutron flux distributions The measurement and calculated results for HEU core fluxes in the center vertical port are given in Table 4-9 of the fuel conversion SAR as follows:

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Table 5. Comparison of Measured and Calculated Foil Reaction Rates in the CVP and Rabbit System (from fuel conversion SAR Table 4-9)

Measured Calculated Ratio Foil ID Foil Type Foil Position Reaction Reaction Rate Measured Rate (relative error) to Calculated I Cd-covered Vertical port 6.77E+09 6.78E+09 1.00 Au (7.47%)

6 Au Vertical port 2.39E+10 2.43E+10 0.98 (3.79%)

2 Cd-covered Vertical port 6.91 E+09 5.80E+09 1.19 Au (8.25%)

7 Au Vertical port 2.23E+10 1.82E+10 1.23 (4.70%)

10,12 Cd-covered Rabbit system 5.96E+09 6.05E+09 0.99 Au (6.10%)

5,11 Au Rabbit system 2.17E+ 10 2.29E+10 1.06 (3.22%)

The details of the calculated HEU and LEU flux distributions for different energy groups (including thermal) are given in Section A.5 of the HEU to LEU fuel conversion SAR.

8. Reactor physics measurements Table 6 shows the measured and calculated reactor physics parameters for the LEU and HEU core.

Table 6. Kinetics Parameters and Reactivity Coefficients Calculated for UFTR Accident Analyses.

HEU Fresh LEU Measured Parameter Core Core LEU Core 3eff P 0.0079 0.0077 N/A Cvoid (Ap , %void) -1.48E-03 -1.53E-03 N/A Cwater (Ap, °C) -5.91E-05 -5.68E-05 -7.33E-5 Cfuel (Ap, °C) -0.29E-05 -1.65E-05 N/A 6

9. Initial LEU core loading Table 7 shows the initial LEU core loading sequence and the measurement results.

Table 7. Detector count rates (cps) during initial LEU core loading No. of loaded Water Water 1 blades 2 blades 3 blades 4 blades fuel bundles down up out out out out No fuel 4.0 4.5 4.5 4.5 4.5 4.5 4 9.5 5.5 5.5 5.0 5.5 5.5 8 10.0 5.5 6.0 6.0 6.0 6.5 10 10.0 6.0 7.5 9.0 7.5 8.0 12 10.5 9.0 9.0 10.0 10.0 10.0 14 10.5 12.0 12.0 12.0 12.0 14.0 16 10.5 12.0 13.0 14.0 17.0 20.0 18 11.0 17.0 20.0 21.0 26.0 28.0 20 13.0 25.0 37.0 40.0 60.0 100.0 21 13.0 30.0 40.0 50.0 N/A N/A 22 13.0 40.0 60.0 100.0 N/A N/A 23 13.0 55.0 100.0 N/A N/A N/A

10. Primary coolant measurements Table 8 shows reactivity measurement results of 100 ml primary water sample along with water samples from secondary coolant and shield tank.

Table 8. Water reactivity measurement results Sample Identification Beta Activity Alpha Activity (uCi/ml) (uCi/ml)

Primary coolant system 1.6E-6 2.5E-8 Secondary Sample Tank <LLD* 5.OE-8 Secondary Heat Exchanger <LLD 4.0E-8 Shield Tank Water <LLD 2.5E-8 LLD: Lower Limit of Detection

11. Discussion of results The current LEU core includes 22 full bundles with two fully dummy bundles. It is concluded that for achieving similar excess reactivity, the B-1 0 concentration in the graphite has to be set to 0.12 ppm. The calculated excess reactivity, shutdown margins, and control blades worths are verified with measurements. The larger observed 7

differences between the calculation and experimental worth of control blades can be attributed to the differences in computation and experimental approaches. Other test results, including the primary water measurements, also confirm that UFTR is operating in normal condition with the LEU fuel. In summary, UFTR has been operating normally with the new LEU fuel.

Reference

1. UFTR LEU fuel loading document: core unloading sequence, 09/ 2007

2. UFTR annual control blade worth measurement, 05/2008 8