ML14205A300

Response to RAI Dated June 19, 2014, Regarding R-113 License Amendment Request

ML14205A300
Person / Time
Site:	U.S. Geological Survey
Issue date:	07/10/2014
From:	DeBey T M US Dept of Interior, Geological Survey (USGS)
To:	Document Control Desk, Office of Nuclear Material Safety and Safeguards
References
TAC ME9424
Download: ML14205A300 (6)

Text

• USGSscience for a changing worldDepartment of the InteriorUS Geological SurveyBox 25046 MS-974Denver CO, 80225July 10, 2014U.S. Nuclear Regulatory CommissionATTN: Document Control DeskWashington DC 20555Subj: Response to RAI dated June 19, 2014, regarding R-113 license amendment request (TAC No.ME9424)Gentlemen:The attached pages are submitted in response to your Request for Additional Information dated June19, 2014. Please contact me if you need additional information.Sincerely,Tim DeBeyUSGS Reactor SupervisorI declare under penalty of perjury that the foregoing is true and correct.Executed on 07/10/2014Copy to:Vito Nuccio, Reactor Administrator, MS 911USGS Reactor Operations Committee Responses to RAI QuestionsResponse to Question 1:It is proposed that License Condition 2.B(2) be changed from the current restriction of enriched uraniumat 93.00 percent to any level of enrichment.BASIS: The basis for the requested change is two-fold. First, the current prescribed enrichment of 93.00percent is assigning more precision to the enrichment value than can be determined, or is specified bythe supplier, for any of the SNM possessed in our existing neutron detectors. Second, the specificationof 93.00 percent enrichment is overly restrictive for the potential use at the facility. Fission chamberneutron detectors may use uranium enriched at various levels, as a method for changing the detector'ssensitivity to fast neutrons. Most reactor instrumentation detectors use uranium enriched to 90% orabove, but other research may benefit from the use of detectors at lower uranium enrichments in orderto enhance fast neutron response.JUSTIFICATION: Research requiring fission chamber neutron detectors can benefit from those detectorshaving enriched uranium at a varying enrichment level. The prior specification of 93.00 percent isunnecessarily and unreasonably restrictive.Response to Question 2:Revised Response to Question 7 of RAI dated January 29, 2014:The amendment request proposes a very minor increase to the mass limit of special nuclear materialcurrently authorized under license R-113 in TRIGA fuel. All TRIGA fuel elements received at the GSTR willbe possessed under the existing SNM limit for TRIGA fuel at the facility. The SNM possessed at the GSTRwill continue to be of low strategic significance, and therefore, within our current license and securityplan. The SNM contained in TRIGA fuel elements possessed at the facility may be utilized but notseparated. A new item of 2 grams of special nuclear material of any enrichment is proposed to allow forreactor experiments, detector calibration, and reference sources related to reactor operation. The effectof the increase of 2 grams of SNM at any enrichment is minimal. The proposed wording for SNMauthorized on the license is:B. Pursuant to the Act and 10 CFR Part 70, "Domestic Licensing of Special NuclearMaterial," in connection with operation of the facility to receive, possess and use (but not separate):(1) up to 9 kilograms of contained uranium-235 enriched to less than 20percent in the isotope uranium-235 in the form of TRIGA reactor fuel;(2) up to 15 grams of contained uranium-235 of any enrichment in the formof neutron detectors; and(3) up to 2 grams of special nuclear material of any enrichment in reactor-basedexperiments, calibration of radiation detectors, and reference sources for reactor basedprograms.(4) such special nuclear material as may be produced by the operation of the facility.1 Response to Question 3:The type of experiment that may be performed using up to 2 grams of special nuclear material couldinvolve irradiation of that material or use of that material as a reference source. The worst casescenario would involve neutron irradiation of 2 grams of SNM to the point where a GSTR technicalspecification limit on iodine inventory (1.5 Ci of 1-131 through 1-135) or strontium inventory (5 mCi of Sr-90) is reached. These limits are given in T.S. 1.9.Any proposed experiment involving irradiation of SNM would have a safety analysis performed, as partof the GSTR experiment review process, to ensure that T.S. 1.9 would not be violated. For example, 2grams of pure U-235 could be irradiated for approximately 9.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> at a neutron flux of 4e12 withoutexceeding T.S. 1.9 limits. An existing GSTR Experiment Authorization allows the irradiation of up to 1.5 gof natural U02 or 10.5 mg of HEU for up to 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> at a neutron flux of 4e12, so that approvedexperiment is well within the limits of T.S. 1.9.The table below summarizes the maximum allowable irradiation times for pure (100%) U-233, U-235,and Pu-239 isotopes, using masses of 2 grams each and a neutron flux (fast and thermal) of 4e12 foreach energy range.Neutron 1-131 Total numberflux Total thru I- of fissions Expt(each, Irrad number of 135 Sr-90 produced in fissionsSNM Mass fast and time fissions in produced produced "hot" fuel rod as % ofisotope (grams) thermal) (hrs) experiment (Ci) (Ci) (22 kW) MHAU-233 2 4.OOE+12 4.15 1.75E+17 1.49 1.18E-07 1.03E+19 1.70U-235 2 4.OOE+12 9.5 4.12E+17 1.49 6.18E-08 2.35E+19 1.75Pu-239 2 4.OOE+12 2.33 1.33E+17 1.49 2.68E-08 5.76E+18 2.31As can be seen from the table, the maximum irradiations that can be performed with the SNM isotopesall produce small fractions of the total fissions (and therefore, fission product inventories) for theMaximum Hypothetical Accident (MHA) analyzed for the GSTR. The scenario that is closes to the MHA isthe irradiation of 2 grams of Pu-239, which produces 2.31% as many fissions as the MHA.Using a ratio of the MHA analysis results, failure and dispersal of the Pu-239 irradiation experiment in airwould conservatively give the following estimated doses to staff members who were present in thereactor room at the time of failure.2 Likewise, failure and dispersal of the Pu-239 irradiation experiment in air would conservatively give thefollowing estimated doses to persons outside of the reactor facility.Distance CDEThyroid (no TEDE (noLocation (m) water) (nrem) water).(mrem)Building 15 south 11 1 1doorEmergency 32 0.3 0.1assembly areaBuilding 21 eastentrance (West 49 1 0.1of Building 15)Average ofeastern 100 0.9 0.06intersectionsBuilding 16 west 175 0.4 0.02entrance200 0.3 0.02-250 0.2 0.01NearestUnrestricted 475 0.06 <0.01Access LocationResidence 640 0.03 <0.01School 720 0.03 <0.01This analysis is based on the MHA analysis that has many conservative factors used, such as no decaytime, the release occurs in air, no filtration of the air, and no containment in the reactor bay. It can beseen that failure of this experiment does not present a significant threat to the reactor staff or nearbymembers of the public. The use of more realistic factors would give significantly lower dose estimates.Response to Question 4:The USGS technical specification on iodine and strontium activities produced in fueled experiments willbe observed for the irradiation of the SNM discussed in this request. As with all GSTR experiments, asafety analysis will be performed to ensure that each experiment authorization for irradiation of SNMwill not violate any requirements of the license, T.S., or procedures. As discussed in the response toQuestion 3 (above), the irradiation times for 2 gram samples of pure SNM would be restricted to thevalues shown in the table below, in order to meet the limits of T.S. 1.9. It is not expected that 2 gramswould be irradiated in any one experiment, so the irradiation time values below are conservative foractual experiments that would be performed. An experiment authorization for irradiation of 0.1 gram ofSNM could allow a significantly longer irradiation time and still meet the T.S. 1.9 requirements.3 Neutron flux Irrad timeSNM Mass (each, fast (hrs) to reachisotope (grams) and thermal) T.S. 1.9 limitsU-233 2 4.00E+12 4.15U-235 2 4.OOE+12 9.5Pu-239 2 4.OOE+12 2.33A new technical specification is not needed, because the experiment review process at the GSTR willensure that T.S. 1.9 requirements are met for all SNM irradiations.Response to Question 5:Our proposed license condition 2.C.l.c has the following sentence: "(Note: following irradiation, if >99%of the radioactivity in the material has been produced in the GSTR, the byproduct material will then beconsidered to be entirely GSTR-produced.)" Our proposed license condition 2.C.1.e has a similar note.The purpose of these notes is to eliminate time-consuming and unproductive inventory accounting workthat has no safety significance.The basis for these notes is licensed material received from other licensees, under proposed licenseconditions 2.C.1, needs to be inventoried on a periodic basis to ensure that the limits of these conditionsare met. The licensed material received from other licensees will decay over time, while most (if not all)of the items will be irradiated at the GSTR. The result is that the originally-received isotope activity willdecrease while GSTR irradiation will produce newly-activated isotopes in that item. If no limit isprovided for the transferred isotope inventory requirement, then vanishingly small values will need tobe calculated, tracked, and recorded with no safety significance.Justification of the proposed notes may be best provided by example. Assume that licensed material (apneumatic sample terminus) containing 0.1 mCi of Cr-51 is received from another TRIGA facility, for useat the GSTR. The Cr-51 isotope has a half-life of about 27.8 days. The terminus is made of 6061aluminum alloy, with 0.3 weight% chromium composition. The terminus is installed in the GSTR where500 grams of the terminus sees a routine neutron flux of 1.36e12 neutrons/cm2-s. After 26 hours3.009259e-4 days <br />0.00722 hours <br />4.298942e-5 weeks <br />9.893e-6 months <br /> ofirradiation, there will have been >10 mCi of Cr-51 produced in the terminus and the Cr-51 received fromthe other licensee will have decayed to <1% of the total Cr-51. In addition, there will have been manymCi of AI-28, Mg-27, and Na-24 also produced in the terminus. The GSTR-produced isotopes willcontinue to grow, while the isotope received from the other licensee diminishes. It is not reasonable atthis point to continue to perform separate accounting of the small amount of Cr-51 remaining from theother licensee. The proposed license condition will allow 100% of the radioactivity in the terminus to beaccounted for as if it was produced in the GSTR.4 Conversely, if an item is received from another licensee and it is not irradiated at the GSTR, then itwould continue to be inventoried as transferred material and it would be subject to the limitations ofproposed license conditions 2.C.1.c and/or 2.C.1.e.Response to Question 6:It is correct that we have not included a license condition to account for SNM produced during operationof the GSTR, so we appreciate your suggested addition of a new condition to include that material. Wepropose adding a new condition 2.B (4):... (4) such special nuclear material as may be produced by the operation of the facility.5