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MONTHYEARML1023100752010-08-13013 August 2010 Request for Additional Information Regarding Financial Qualifications for the License Renewal Review Project stage: Request ML1024400342010-08-25025 August 2010 Request for Additional Information Regarding the Application for License Renewal Project stage: Request ML1030701252010-10-19019 October 2010 Letter Armed Forces Radiobiology Research Institute - Approval of Request for an Extension Response to Request for Additional Information Dated July 19, 2010 Project stage: Response to RAI ML1030701212010-10-21021 October 2010 Letter Armed Forces Radiobiology Research Institute-Request for Additional Information Regarding the Application for License Renewal Project stage: Request ML1104606872011-02-0707 February 2011 Request for Additional Information Regarding the Application for License Renewal Project stage: Request ML11165A0162011-06-0303 June 2011 Armed Forces Radiobiology Research Institute, Response to Request for Additional Information Dtd 07/19/2010 Regarding the Application for License Renewal Project stage: Response to RAI ML11269A0302011-09-0606 September 2011 Response to Request for Additional Information Regarding the Application for Renewal of License R-84 Project stage: Response to RAI ML11341A1332011-11-28028 November 2011 Esponse to Request for Additional Information Regarding the Application for License Renewal Project stage: Request ML12032A0542012-01-17017 January 2012 Response to Request for Additional Information Regarding the Application for License Renewal Project stage: Response to RAI ML15296A4512012-04-20020 April 2012 21C025, Rev. 0, Bloost Code Validation Report. Project stage: Other ML12122A1462012-04-20020 April 2012 Request for Additional Information Regarding the Application for License Renewal Project stage: Request ML12272A3032012-09-21021 September 2012 Request for Additional Information Regarding the Application for License Renewal Project stage: Request ML1018000132012-10-26026 October 2012 Armed Forces Radiobiology Research Institute - Determination of Acceptability and Sufficiency for Docketing and Opportunity for a Hearing Regarding the Application for Renewal of Facility License No. R-84 for the Afrri Reactor Project stage: Other ML13182A0842013-06-28028 June 2013 Armed Forces Radiobiology Research Institute - Response to Request for Additional Information Regarding the Application for License Renewal Project stage: Response to RAI ML13254A0642013-08-27027 August 2013 Us Dept of Defense, Uniformed Services University of the Health Sciences - Submittal of Revised Technical Specifications, Docket 50-170 Project stage: Request ML14115A1692014-05-16016 May 2014 Armed Forces Radiobiology Research Institute (Afrri) - Request for Additional Information for the for the License Renewal Review of the Afrri Reactor Facility Project stage: RAI ML14349A3192014-12-0404 December 2014 Request for Additional Information Regarding the Renewal of Facility Operating License No. R-84 for the Afrri Triga Reactor Facility Project stage: Request ML15026A4192015-02-23023 February 2015 Request for Additional Information Physical Security Plan Review for License Renewal Project stage: RAI ML15093A0992015-03-30030 March 2015 Letter from Stephen L. Miller Enclosing Revision of the Technical Specifications for the Armed Forces Radiobiology Research Institute Reactor (License R-84, Docket 50-170) Project stage: Request ML15182A2392015-06-25025 June 2015 Us Dept of Defense, Armed Forces Radiobiology Research Institute - Response to Request for Additional Information Regarding the Physical Security Plan Review for License Renewal Project stage: Response to RAI ML15273A4772015-11-0202 November 2015 Armed Forces Radiobiology Research Institute (Afrri) - Request for Additional Information Regarding the Renewal of Facility Operating License No. R-84 for the Afrri Triga Reactor Facility Project stage: RAI ML15317A0142015-11-0404 November 2015 Response to Armed Forces Radiobiology Research Institute - Request for Additional Information Regarding Physical Security Plan Review for License Renewal Project stage: Request ML16040A3102016-02-0909 February 2016 Request for Additional Information Regarding the Application for License Renewal Project stage: Request ML16060A2102016-02-26026 February 2016 Submittal of Technical Specifications for the Armed Forces Radiobiology Research Institute Facility Project stage: Request ML16089A3732016-03-23023 March 2016 Armed Forces Radiobiology Research Institute - Transmittal of 2015 Annual Operating Report Project stage: Request ML16232A1642016-08-0505 August 2016 Response to NRR Request for Additional Information Regarding the Application for License Renewal for Affri Facility Project stage: Request ML16232A1672016-08-0505 August 2016 Technical Specifications for the Affri Reactor Facility Project stage: Other ML16232A1662016-08-0505 August 2016 Response to NRR Request for Additional Information Regarding the Renewal of the Armed Forces Radiobiology Research Institute, Triga Reactor Facility Project stage: Request ML16218A2242016-08-0505 August 2016 Armed Forces Radiobiology Research Institute TRIGA Research Reactor proposed license renewal IPaC Trust Resources Report Project stage: Request ML16258A4642016-09-12012 September 2016 Reactor Operator Requalification Program for the Affri Triga Reactor Facility Project stage: Request ML16258A4632016-09-12012 September 2016 Us Dept of Defense, Armed Forces Radiobiology Research Institute (Afrri), Submittal of Request for Additional Information Regarding the Application for License Renewal Project stage: Request ML16253A2342016-09-15015 September 2016 Afrri Request for Additional Information for License Renewal Project stage: RAI ML16267A4472016-09-21021 September 2016 Request for Additional Information Regarding the Application for License Renewal Project stage: Request ML16278A1112016-09-30030 September 2016 Us Dept. of Defense, Armed Forces Radiobiology Research Institute (Afrri), Response to Request for Additional Information Regarding Application for License Renewal Project stage: Response to RAI ML16077A3022016-09-30030 September 2016 AFRRI Technical Specifications Project stage: Request ML16321A4612016-11-16016 November 2016 Us Armed Forces Radiobiology Research Institute Letter Regarding Review of Draft License R-84 Project stage: Request ML13211A1912016-11-18018 November 2016 Armed Forces Radiobiology Research Institute - Environmental Assessment and Finding of No Significant Impact Regarding Renewal of Facility Operating License No. R-84.) Project stage: Other ML13211A1902016-11-18018 November 2016 Environmental Assessment and Finding of No Significant Impact Regarding License Renewal for the Armed Forces Radiobiology Research Institute (Afrri) Triga Mark-F Research Reactor (FRN) Project stage: Other ML16077A2842016-11-30030 November 2016, 1 December 2016 Afrri Renewal of Facility Operating License Project stage: Request ML16278A3472016-11-30030 November 2016 SER: Renewal of the Facility Operating License for the Armed Forces Radiobiology Research Institute TRIGA Reactor Project stage: Request ML16077A3032016-11-30030 November 2016 Armed Forces Radiobiology Research Institute - Issuance of Renewed Facility Operating License No. R-84 for the Armed Forces Radiobiology Research Institute Research Reactor Project stage: Approval ML16077A3012016-12-0101 December 2016 Federal Register Notice - Afrri License Issuance Project stage: Other NRC-2012-0272, Federal Register Notice - Afrri License Issuance2016-12-0101 December 2016 Federal Register Notice - Afrri License Issuance Project stage: Other 2015-11-02
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Category:Letter
MONTHYEARIR 05000170/20232012023-09-26026 September 2023 Armed Forces Radiobiology Research Institute - U.S. Nuclear Regulatory Commission Safety Inspection Report No. 05000170/2023201 ML23163A2262023-08-10010 August 2023 Examination Result Letter No. 50-170/OL-23-01, Armed Forces Radiobiology Research Institute ML23214A1552023-07-13013 July 2023 Uniformed Services University of the Health Sciences - Change of Director at the Uniformed Services University of the Health Sciences (Usuhs), Armed Forces Radiobiology Research Institute (Afrri) in Bethesda, Maryland ML23163A2252023-06-13013 June 2023 Examination Report Letter No. 50-170/OL-23-01, Armed Forces Radiobiology Research Institute ML23040A4612023-05-0404 May 2023 Examination Confirmation Letter No. 50-170-OL-23-01, Armed Forces Radiobiology Research Institute ML23080A0162023-03-10010 March 2023 2022 Annual Operating Report for the Armed Forces Radiobiology Research Institute (Afrri) ML22263A2382022-09-12012 September 2022 Uniformed Services Univ. of the Health Sciences - Letter of Reply to the Event Report No. 54349 IR 05000170/20222012022-08-24024 August 2022 Armed Forces Radiobiology Research Institute - U.S. Nuclear Regulatory Commission Safety Inspection Report No. 05000170/2022201 ML22131A3712022-06-27027 June 2022 Armed Forces Radiobiology Research Institute - Issuance of Amendment No. 26 to Renewed Facility Operating License No. R-84 ML22118A8682022-04-28028 April 2022 Armed Forces Radiobiology Research Institute (Afrri) - Supplement to the License Amendment Request for the Digital Instrumentation and Control Upgrade ML22096A2802022-04-0404 April 2022 Uniformed Services Univ. of the Health Sciences, Armed Forces Radiobiology Research Institute (Afrri), Submittal of Supplement to License Amendment Request for the Digital Instrumentation and Control Upgrade ML22090A1762022-03-31031 March 2022 Submittal of 2021 Annual Operating Report Required by the Technical Specifications for the Armed Forces Radiobiology Research Institute (Afrri) Facility Operating License No. R-84, Docket 50-170 ML22067A2462022-03-29029 March 2022 Armed Forces Radiobiology Research Institute (Afrri) Digital Instrumentation and Control (I&C) Audit Report ML21362A7662022-01-14014 January 2022 Armed Forces Radiobiology Research Institute Routine Inspection Report No. 05000170_2021203 ML22007A2642022-01-0707 January 2022 Us Dept. of Defense, Uniformed Services Univ. of the Health Sciences - the Armed Forces Radiobiology Research Institute (Afrri) Is Submitting a Supplement to the License Amendment Request for the Digital Instrumentation and Control Upgrade ML21327A3812021-12-30030 December 2021 Examination Confirmation Letter No. 50-170/OL-22-01, Armed Forces Radiobiology Research Institute ML21316A0332021-11-0808 November 2021 Afrri - LAR - Digital IC - Functional Requirement Specification ML21302A0972021-10-28028 October 2021 Afrri LAR for the Digital Instrumentation and Control Upgrade Revision 1 ML21270A0672021-10-22022 October 2021 Letter - Armed Forces Radiobiology Research Institute - Exemption from 10 CFR 55.31(a)(5) and 55.45(b) ML21302A1072021-10-15015 October 2021 Enclosure 4 - Affidavit for Proprietary Information ML21285A0252021-10-0707 October 2021 Afrri - RO Licensing Exemption Request Supplemental Information ML21260A1842021-09-17017 September 2021 Us Dept of Defense, Uniformed Services Univ. of the Health - Afrri Exemption Request for Licensing of Reactor Operators ML21253A0012021-09-13013 September 2021 Us Department of Defense Armed Forces Radiology Research Institute - Regulatory Audit Plan for Digital Instrumentation and Control System Upgrade IR 05000170/20212022021-08-24024 August 2021 Armed Forces Radiobiology Research Institute - U.S. Nuclear Regulatory Commission Routine Inspection Report No. 05000170/2021202 IR 05000170/20212012021-08-24024 August 2021 Armed Forces Radiobiology Research Institute - Nuclear Regulatory Commission Security Inspection Report No. 05000170/2021201 (Public) ML21138A9092021-05-14014 May 2021 Uniformed Services Univ. of the Health Sciences, Interim Reactor Facility Director Change Update ML21316A0372021-04-27027 April 2021 Enclosure 4 - Affidavit for Proprietary Information ML21089A1212021-03-29029 March 2021 Uniformed Services Univ. of the Health Sciences - 2020 Annual Operating Report ML21053A2672021-02-25025 February 2021 Armed Forces Radiobiology Research Institute Acceptance of the Application for a Llicense Amendment Digital Instrumentation and Control Upgrade ML21042B8412021-02-11011 February 2021 Transmittal of Proposed Changes to the Technical Specifications in Support of the License Amendment Request for the Digital Instrumentation and Control Upgrade for the Afrri Triga Reactor ML21041A1652021-02-10010 February 2021 EA-2020-056, Armed Forces Radiobiology Research Institute, Relaxation Letter ML21036A2972021-02-0505 February 2021 Response to NRC 01/08/2021 Letter Re License Amendment Request for Facility Operating License No. R-84 for the Afrri Triga Reactor Docket No. 50-170 IR 05000170/20202012021-01-14014 January 2021 Armed Forces Radiobiology Research Institute - Nuclear Regulatory Commission Routine and Follow-up Inspection Report No. 05000170/2020201 ML20303A2062020-11-19019 November 2020 Cover Letter to Confirmatory Order and NRC Investigation Report 1-2019-003 to Armed Forces Radiobiology Research Institute (EA-20-056) ML20318A3392020-11-10010 November 2020 Afrri LAR for Digital I&C Upgrade ML20322A0372020-11-0909 November 2020 Signed Consent and Hearing Waiver from Armed Forces Radiobiology Research Institute (EA-20-056) ML20108F5342020-03-30030 March 2020 2019 Annual Operating Report Required by the Technical Specifications for the Armed Forces Radiobiology Research Institute Reactor (License R-84, Docket 50-170) ML20023C3412020-03-0303 March 2020 Armed Forces Radiobiology Research Institute - U.S. Nuclear Regulatory Commission Notice of Violation IR 05000170/20192032019-12-30030 December 2019 Armed Forces Radiobiology Research Institute - U.S. Nuclear Regulatory Commission Reactive Inspection Report 05000170/2019203 ML19357A0622019-12-13013 December 2019 Armed Forces Radiobiology Research Institute (Afrri) - Change in Afrri Licensee (Level I Management), Docket No. 50-170, License R-84 ML19281C3322019-09-0505 September 2019 Appointment of Walter (Dale) Tomlinson as the Reactor Facility Director for the Armed Forces Radiobiology Research Institute (Afrri) Training; Docket 50-170, License R-84 ML19058A3272019-08-14014 August 2019 Armed Forces Radiobiology Research Institute - Issuance of Amendment No. 25 Regarding Changing the Required Qualifications of Reactor Facility Director Per Technical Specification 6.1.3.1.B. and 6.2.5 Audit Frequencies IR 05000170/20192022019-07-17017 July 2019 Armed Forces Radiobiology Research Institute - Nuclear Regulatory Commission Reactive Safety Conscious Work Environment Issue of Concern Follow-Up Interim Inspection Report No. 05000170/2019-202-0004 ML19170A1052019-06-0606 June 2019 Us Dept. of Defense, Armed Forces Radiobiology Research Institute - Reply to Notice of Violation Dated May 10, 2019 ML19087A1272019-03-18018 March 2019 Us Dept. of Defense, Uniformed Services Univ. of the Health Sciences - Submittal of 2018 Annual Operating Report IR 05000170/20192012019-03-14014 March 2019 Armed Forces Radiobiology Research Institute - U.S. Nuclear Regulatory Commission Routine Inspection Report No. 05000170/2019201 ML19101A1932019-02-27027 February 2019 Armed Forces Radiobiology Research Institute (Afrri) - License Amendment Request (LAR) for Reactor Facility Director (Rfd) Qualification Tech Spec, Operations Minimum Staff Tech Spec, and Audit Function Tech Spec, Docket No. 50-170, License ML18347B3852018-12-14014 December 2018 Armed Forces Radiobiology Research Institute - Acceptance of Requested Licensing Action Regarding License Amendment for Changing the Required Qualifications of Reactor Facility Director for the Armed Forces Radiobiology Research Institute . ML18354A7292018-12-0606 December 2018 Us Dept. of Defense, Uniformed Services Univ. of the Health Sciences - One Time Fuel Movement at the Armed Forces Radiobiology Research Institute Reactor Facility ML18318A3062018-11-0808 November 2018 Us Dept of Defense, Uniformed Services Univ. of the Health Sciences - Submittal of License Amendment Request (LAR) for Reactor Facility Director (Rfd) Qualification Tech Spec, Operations Minimum Staff Tech Spec, and Audit Function Tech Spec 2023-09-26
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mARMED FORCES RADIOBIOLOGY RESEARCH INSTITUTE 8901 WISCONSIN AVENUE BETHESDA, MARYLAND 20889-5603
- 0) September 21, 2012 Nuclear Regulatory Commission ATFN: Document Control Desk Washington, DC 20555-0001
SUBJECT:
REQUEST FOR ADDITIONAL INFORMATION REGARDING THE APPLICATION FOR LICENSE RENEWAL (TAC NO. ME1587)Sir: The Nuclear Regulatory Commission previously requested additional information necessary to allow processing of our research reactor license renewal application (License R-84, Docket 50-170). We are now submitting revised answers to three of those questions.
The enclosed revised answers replace the original submission as indicated:
- 1. Response to Question 6 of first RAI set. Originally submitted on April 20,2012.2. Response to Question 18 of first RAI set. Last submitted on October 20, 2011.3. Response to Question 3b of second RAI set. Originally submitted on October 21, 2010.If you need further information, please contact Mr. Steve Miller at 301-295-9245 or I declare under penalty of perjury that the foregoing and all enclosed information is true and correct to the best of my knowledge.
Executed n September 21, 2012.
Enclosures:
L REW HUFF as COL, SAF Acting Director-" ' " ...-" " I ." ! ... " '?. ,'
- 6. NUREG-1537 Part 1,Section 13 provides guidance to the licensee to discuss potential occident scenarios.
Section 13.1.5 of the SAR presents the results of an analysis of a reactivity insertion of $0.51. Justify the magnitude of this assumed reactivity insertion In comparison with the maximum reactivity Insertion associated with any single experiment.
The following analysis will replace the reference to a reactivity insertion of $0.51 of the SAR: The failure of an experiment or experiments could result in Instantaneous insertion of reactivity.
The worst possible case would be the prompt addition of $3.00 (2.1% Ak/k) within the reactor core. The Technical Specifications establish that the sum of the absolute reactivity worths of all experiments in the reactor and in the associated experimental facilities shall not exceed $3.00 (2.1% Ak/k). The instantaneous insertion of $3.00 (2.1% Ak/k) to the reactor core as a result of a worst case reactivity insertion is bounded by the analysis of the $3.50 (2.45%Ak/k) pulse limit and would not result in any adverse safety conditions within the AFRRI TRIGA core.In addition to this analysis, the loss-of-coolant (LOCA) scenario has been updated to reflect the 1.1 MW licensed power limit. The following analysis will be added to SAR Section 13.2.1.3.As described in 13.2.1 of the AFRRI SAR, the reactor fuel elements rely on ambient air natural convection through the core to cool the reactor fuel In the event of a loss-of-coolant accident (LOCA). A buoyancy force to drive this natural convection is developed by a hot air column within the core and a cooler column of air outside of the core. This accident has been analyzed for an instantaneous loss of water and a loss of water occurring over a 15 minute period. In addition, this analysis indudes scenarios for infinite full power operation and 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> per week operation over a 40 year period.If all reactor coolant was suddenly lost, the primary concern would be the integrity of the fuel cladding.
Maintaining a fuel cladding temperature below the NUREG-1282 specification of 950 0 C ensures that the cladding maintains sufficient strength to prevent failure under the pressure of hydrogen gas buildup within the element. Therefore, operating conditions must be such that In the event of a LOCA the fuel cladding temperature will not exceed 950 0 C.General Atomics Report No. E-1 17-196 provides a detailed analysis showing that air natural convection cooling Is adequate to maintain fuel cladding below 900*C assuming power levels no higher than 21 kW per element are achieved.
This calculation assumes an instantaneous loss of all coolant and Infinite operation at 1 MW. If a 15 minute delay between reactor scram and total coolant loss is assumed, fuel cladding will remain below 900 0 C up to a power level of 22 kW per element. Analysis provided In the Oregon State TRIGA Reactor SAR shows that if reactor operating history Is assumed to be 70 MW-hrs per week over a 40 year period, these limits for maximum power level per element increase to 25.2 and 26.4 kW, respectively.
As described in 13.2.1.3 of the AFRRI SAR, assuming an operational history of 72 MW-hrs per week for 40 years, maximum fuel cladding temperatures following LOCA are 548 0 C assuming instantaneous coolant loss and 477 0 C assuming a 15 minute delay time. These calculations assume operation at 1 MW.The current maximum licensed steady state power of the AFRRI reactor is 1.1 MW. Section 4.5.8 of the AFRRI SAR discusses the power peaking within the 85-3 core and determines the highest power factor of 1.552 to occur in position B04. Assuming 1.1 MW with 88 fuel elements, the B04 element has a power of 19.4 kW. This is within the 21 kW per element limit set for the worst-case LOCA, and substantially less than the more representative 26.4 kW per element limit. In reality, AFRRI's operating history is far below 70 MW-hours per week, with a historical average closer to 500 kW-hours per week.(Revised September 21, 2012)
- 18. TS 3.1.2: ANSI/ANS-15.1-2007, Section 3.1(3) provides guidance for the LCO for pulse limits.In TS 3.1.2, the LCO for pulse mode operatiOns specifies the maximum step insertion of reactivity shall be $4.00 in the pulse mode. Anaolyses performned by the licensee indicate that this magnitude pulse may achieve a peak fuel temperature that exceeds the fuel vendor's recently recommended peak temperature of 830 degrees C during pulse mode operations.
Please analyze and discuss how TS 3.2.1 should be revised to meet the fuel vendor recommendation.
TS 3.1.2 has been modified to change the maximum allowable pulse size to $3.50. This smaller size pulse will not affect AFRRI operations since experimental pulses over $3.50 have not been required in more than 20 years and are not expected to be needed in the future. The TS basis has been revised to indicate the current temperature analysis from the new Safety Analysis Report Chapter 4 submitted on March 4, 2010.The Limiting Safety System Setting from the TS will remain at 600 0 C. Maintaining a fuel cladding temperature below the NUREG-1282 specification of 9500C (when the cladding equals the fuel temperature) ensures that the cladding maintains sufficient strength to prevent failure under the pressure of hydrogen gas buildup within the element. This 950 0 C temperature limit does not account for the cooling provided by the primary water and thus yields a conservative value. When fuel cladding is maintained below 500tC, a peak fuel temperature limit of 11500C is recommended.
The AFRRI TRIGA Limiting Safety System Setting specified in the Technical Specifications Is 600f. This provides a significant safety margin to ensure the Safety Limit Is not exceeded during reactor operations.
There are two fuel temperature monitoring channels within the reactor core (one in the B ring and one In the C ring). The highest power density occurs in these two rings, and therefore provides temperature monitoring in the hottest locations of the reactor core. Table 4-14 of the AFRRI SAR identifies the rod power factors for each fuel location in the reactor core. Within the B ring, the highest and lowest power factors are 1.552 and 1.525, respectively.
Assuming the instrumented fuel element (IFE) is located in the lowest power density position (801), a temperature indication of 6000C would yield a peak temperature at the highest power density location (B04) of 6110C. This value is well within the conservative NUREG-1282 limit of 950WC.Within the C ring, the highest and lowest power factors are 1.438 and 1.374, respectively.
Assuming the instrumented fuel element (IFE) is located in the lowest power density position (C12), a temperature indication of 6000C would yield a peak temperature at the highest power density location (C09) of 628 0 C Similarly, this value is well within the conservative NUREG-1282 limit of 9500C.(Revised September 21, 2012) 3b. Where Is the person located? If this dose Is ftom immersion in the Ar-41 plume when it reaches ground level, confirm that a higher dose is not possible from radiation shine from the plume passing over a person closer to the focility than the point at which the plume reaches ground level or from a person exposed to direct radiation shine from the Ar-41 source before release from the AFRRI research reoctor focility.In order to provide a thorough evaluation of the consequences from Ar-41 release, the following will address the estimated doses to members of the public outside of the AFRRI facility and radiation workers within the reactor room.Theoretical Dose to Members of the Public from Ar-41 Release The following analysis illustrates that even under operating conditions that are orders of magnitude above those found at AFRRI, no member of the public will exceed the 10 CFR 20 limit of 100 mrem as a result of Ar-41 release during reactor operations.
The maximally exposed member of the public is located at the Zachary and Elizabeth Fisher House, 91 meters from the AFRRI research reactor stack. This location represents the closest"full occupancy" area, e.g. an area occupied full-time by an individual or permanent residence position from the AFRRI research reactor stack. Other features located less than 91 meters from the AFRRI research reactor stack are roads, sidewalks, parking lots, parking garages, and the AFRRI front or rear patios. None of the aforementioned outdoor areas could be considered either a permanent residence or a full occupancy area.In order to calculate the theoretical dose to a person exposed to direct radiation shine from an Ar-41 source released from the AFRRI research reactor facility, simulations were conducted utilizing MicroSkyshineg.
If we assume continuous 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of operation at 1 MW with an Ar-41 production rate of 5.1 ptCi/sec, we obtain a value of 0.44 Ci of Ar-41. If, for the sake of conservatism, 0.44 Ci is rounded to 0.5 Ci, and we presume a member of the public was standing ten feet from the AFRRI building exterior, the exposure rate from direct radiation shine would be approximately 0.023 mR/hr (0.00023 mSv/hr).In radiation protection, the occupancy factor for an area is defined as the average fraction of time that the maximally exposed individual is present while radiation is being produced.
NCRP Report No. 151 "Structural Shielding Design and Evaluation from Megavoltage X- and Gamma-ray Radiotherapy Fadlities" recommends an occupancy factor of 1/40 for outdoor areas with only transient pedestrian or vehicular traffic, unattended parking lots, vehicular drop off areas (unattended), stairways, and unattended elevators.
Applying this 1/40w occupancy factor to an 8,760-hour year results in an occupancy time of 219 hours0.00253 days <br />0.0608 hours <br />3.621032e-4 weeks <br />8.33295e-5 months <br />, resulting in a dose of 5 mR in a year, well below 10 CFR 20 limits.
If we apply the NCRP-recommended occupancy factor of 1/20 for outdoor areas with seating (the AFRRI patios) to an 8,760-hour year, the result is an occupancy time of 438 hours0.00507 days <br />0.122 hours <br />7.242063e-4 weeks <br />1.66659e-4 months <br />, resulting in a dose of 10 mR in a year. If, for the sake of conservatism, we assume the occupancy time was increased to a standard 2,000-hour working year with an occupancy factor of 1 (100%), the resulting 46 mR dose to a member of the public remains well below 10 CFR 20 limits. In practice, the perimeter of AFRRI is continually monitored by AFRRI security personnel to discourage loitering; hence the occupancy of these outdoor areas is limited to well below the occupancy times recommended in NCRP Report No. 151.Theoretical Dose to Radiation Worker within the Reactor Room from Ar-41 The following analysis illustrates that even under operating conditions that are orders of magnitude above those found at AFRRI, no radiation worker will exceed the 10 CFR 20 limit of 5 rem as a result of Ar-41 release during reactor operations.
The reactor room is posted as a high radiation area and a Reactor Controlled Area. This means that all personnel entering the room must be equipped with dosimetry per AFRRI Instruction 6055.8F "Radiation Protection Program." All dosimeters for AFRRI radiation workers are analyzed approximately quarterly and flagged if they exceed AFRRI ALARA limits, which are established below 10 CFR 20 limits. The AFRRI personnel monitoring program ensures that no personnel will exceed 10 CFR 20 limits as a result of Ar-41 release into the reactor room during operations.
As described in the AFRRI SAR, the equilibrium Ar-41 concentration in the reactor room during operation at 1 MW is 3.2 x 10U jLCi/cm 3.Although this concentration exceeds the 10 CFR 20 DAC of 3 x1 4 i LCi/cm 3 , in an absolute worst case scenario a radiation worker remaining in the reactor room for an entire working quarter (520 hours0.00602 days <br />0.144 hours <br />8.597884e-4 weeks <br />1.9786e-4 months <br />) while the reactor was continuously operated at 1 MW would receive an approximate dose of 1.3 rem. This dose exceeds the AFRRI ALARA limit and would trigger an investigation into the radiation worker's dose and a limit on their exposures for the remainder of the year, thus ensuring that the worker would never exceed 10 CRF 20 limits. For comparison, to achieve the 5 rem dose described in 10 CFR 20, the reactor must operate at 1 MW during the entire working year (2,000 MW-hrs) while the historical operating records at AFRRI indicate an average annual operation of 20 MW-hrs. A radiation worker remaining in the reactor room for all 20 MW-hrs of operation in a single year would receive an approximate dose of 53 mrem, -10% of the 10 CFR 20 limit.(Revised September 21, 2012)