|
---|
Category:Report
MONTHYEARML24166A1982024-06-0707 June 2024 NIST - Independent Third-Party Second Nuclear Safety Culture Assessment, Revision 1 ML24064A1992024-03-0101 March 2024 Us Dept. of Commerce, National Institute of Standards & Technology (NIST) - Change to the Nbsr Requalification Plan in Response to an NRC Request for Additional Information (ADAMS Accession No. ML22223A146) ML24064A0282024-02-29029 February 2024 Requalification Program for the Nbsr ML24023A6212023-12-0606 December 2023 Us Dept. of Commerce, National Institute of Standards & Technology - Problem Identification and Resolution (Pi&R) Performance Area Assessment Report ML24023A6192023-10-23023 October 2023 NIST Center for Neutron Research Reactor Operations and Engineering (NCNR-ROE) Assessment of NCNR-ROE Procedures Program ML24023A6222023-09-0505 September 2023 Final Report - Safety Evaluation Committee (Sec)/Safety Assessment Committee (Sac) ML24023A6232023-09-0101 September 2023 Independent Nuclear Safety Consultant Assessment of Training at the NIST Center for Neutron Research (NCNR) - Final ML24023A6202023-07-11011 July 2023 Independent Nuclear Safety Consultant Assessment of the Root Cause Analysis Performed by NCNR Into the February 3, 2021 Event at the NIST Center for Neutron Research, Revision 1 ML23207A0412023-06-0202 June 2023 Us Dept. of Commerce, National Institute of Standards & Technology, Independent Third-Party Nuclear Safety Culture Assessment of the NIST Center for Neutron Research ML23040A3402023-03-0909 March 2023 NIST Restart Authorization Technical Evaluation Report ML22293B8082022-10-19019 October 2022 National Institute of Standards & Technology (NIST) - License Amendment Request ML22350A0692022-08-19019 August 2022 Us Dept. of Commerce, National Institute of Standards & Technology (Nist), Response to Request for Additional Information on License Amendment Request - Gamma Spectrum Analysis Report ML22227A1502022-08-15015 August 2022 Us Dept of Commerce, National Institute of Standards & Technology (Nist), Request NRC Permission to Restart the Reactor Upon Completion of Listed Corrective Actions and Recovery Efforts ML22223A1462022-08-11011 August 2022 Docket Number 50-184 and the Nbsr Requalification Plan ML21340A0072021-12-0303 December 2021 Analysis of Cooling Flow Through 29 Fuel Elements with Fuel Element 1175 Dislodged ML21294A3722021-10-21021 October 2021 National Institute of Standards and Technology - Supplement to October 1, 2021 Report and Restart Request ML21288A5532021-10-15015 October 2021 NIST Center for Neutron Research - Problem Identification and Resolution ML21274A0252021-09-30030 September 2021 Corrective Action Plan Corrective Actions Required Prior to Reactor Startup ML21274A0262021-09-30030 September 2021 Corrective Action Plan Corrective Actions Required Post-startup ML21274A0232021-09-21021 September 2021 Latch Improvement Safety Analysis ML21274A0222021-09-20020 September 2021 Root Cause Response, Revision 1 ML21274A0192021-09-13013 September 2021 NCNR Twg Report Root Cause Investigation of February 2021 Fuel Failure, Revision 2 ML21274A0212021-08-12012 August 2021 Final Report Sec Subcommittee Report: Review of the NCNR Event Response and Technical Working Root Cause Analysis and Corrective Action Plan ML21274A0202021-06-0303 June 2021 NCNR Twg Report Addendum to Root Cause Investigation of February 2021 Fuel Failure ML21153A3972021-06-0202 June 2021 Requalification Program for the Nbsr ML21340A0082021-05-17017 May 2021 Heat Transfer in a Disc Wedged Between Two Fuel Element Plates ML18157A1382018-05-31031 May 2018 Technical Evaluation of the Preliminary Safety Evaluation Report Supporting the Conversion to Low-Enriched Uranium Fuel for the National Bureau of Standards Reactors ML0907001322009-03-0303 March 2009 Us Dept. of Commerce, NIST, Response to Request for Additional Information on Operator Requalification Program 2024-06-07
[Table view] Category:Technical
MONTHYEARML24166A1982024-06-0707 June 2024 NIST - Independent Third-Party Second Nuclear Safety Culture Assessment, Revision 1 ML24064A1992024-03-0101 March 2024 Us Dept. of Commerce, National Institute of Standards & Technology (NIST) - Change to the Nbsr Requalification Plan in Response to an NRC Request for Additional Information (ADAMS Accession No. ML22223A146) ML24064A0282024-02-29029 February 2024 Requalification Program for the Nbsr ML24023A6212023-12-0606 December 2023 Us Dept. of Commerce, National Institute of Standards & Technology - Problem Identification and Resolution (Pi&R) Performance Area Assessment Report ML24023A6192023-10-23023 October 2023 NIST Center for Neutron Research Reactor Operations and Engineering (NCNR-ROE) Assessment of NCNR-ROE Procedures Program ML24023A6222023-09-0505 September 2023 Final Report - Safety Evaluation Committee (Sec)/Safety Assessment Committee (Sac) ML24023A6232023-09-0101 September 2023 Independent Nuclear Safety Consultant Assessment of Training at the NIST Center for Neutron Research (NCNR) - Final ML24023A6202023-07-11011 July 2023 Independent Nuclear Safety Consultant Assessment of the Root Cause Analysis Performed by NCNR Into the February 3, 2021 Event at the NIST Center for Neutron Research, Revision 1 ML23207A0412023-06-0202 June 2023 Us Dept. of Commerce, National Institute of Standards & Technology, Independent Third-Party Nuclear Safety Culture Assessment of the NIST Center for Neutron Research ML23040A3402023-03-0909 March 2023 NIST Restart Authorization Technical Evaluation Report ML22293B8082022-10-19019 October 2022 National Institute of Standards & Technology (NIST) - License Amendment Request ML22350A0692022-08-19019 August 2022 Us Dept. of Commerce, National Institute of Standards & Technology (Nist), Response to Request for Additional Information on License Amendment Request - Gamma Spectrum Analysis Report ML22223A1462022-08-11011 August 2022 Docket Number 50-184 and the Nbsr Requalification Plan ML21340A0072021-12-0303 December 2021 Analysis of Cooling Flow Through 29 Fuel Elements with Fuel Element 1175 Dislodged ML21288A5532021-10-15015 October 2021 NIST Center for Neutron Research - Problem Identification and Resolution ML21274A0252021-09-30030 September 2021 Corrective Action Plan Corrective Actions Required Prior to Reactor Startup ML21274A0262021-09-30030 September 2021 Corrective Action Plan Corrective Actions Required Post-startup ML21274A0232021-09-21021 September 2021 Latch Improvement Safety Analysis ML21274A0222021-09-20020 September 2021 Root Cause Response, Revision 1 ML21274A0192021-09-13013 September 2021 NCNR Twg Report Root Cause Investigation of February 2021 Fuel Failure, Revision 2 ML21274A0212021-08-12012 August 2021 Final Report Sec Subcommittee Report: Review of the NCNR Event Response and Technical Working Root Cause Analysis and Corrective Action Plan ML21274A0202021-06-0303 June 2021 NCNR Twg Report Addendum to Root Cause Investigation of February 2021 Fuel Failure ML21153A3972021-06-0202 June 2021 Requalification Program for the Nbsr ML21340A0082021-05-17017 May 2021 Heat Transfer in a Disc Wedged Between Two Fuel Element Plates ML18157A1382018-05-31031 May 2018 Technical Evaluation of the Preliminary Safety Evaluation Report Supporting the Conversion to Low-Enriched Uranium Fuel for the National Bureau of Standards Reactors 2024-06-07
[Table view] Category:Response to Request for Additional Information (RAI)
MONTHYEARML22350A0682022-12-13013 December 2022 Us Dept. of Commerce, National Institute of Standards & Technology (Nist), Response to Request for Additional Information on License Amendment Request ML22350A0672022-12-13013 December 2022 Us Dept. of Commerce, National Institute of Standards & Technology (Nist), Response to Request for Additional Information on License Amendment Request ML22322A2112022-11-17017 November 2022 NIST Center for Neutron Research, License Amendment Request. Response to NRC Questions Regarding the Primary and Effluent Monitoring Systems ML22350A0692022-08-19019 August 2022 Us Dept. of Commerce, National Institute of Standards & Technology (Nist), Response to Request for Additional Information on License Amendment Request - Gamma Spectrum Analysis Report ML21340A0102021-12-0303 December 2021 NCNR Response to November 17, 2021 Request for Supplemental Information ML21340A0072021-12-0303 December 2021 Analysis of Cooling Flow Through 29 Fuel Elements with Fuel Element 1175 Dislodged ML21340A0082021-05-17017 May 2021 Heat Transfer in a Disc Wedged Between Two Fuel Element Plates ML17333A1242017-11-17017 November 2017 Supplement for Request for Changes to Nbsr Technical Specifications to Allow Low Power Testing ML17324A4412017-11-17017 November 2017 Supplement for Request for Changes to Nbsr Technical Specifications to Allow Low Power Testing ML17284A1812017-10-0505 October 2017 U.S. Dept. of Commerce, National Institute of Standards & Technology (NIST) - Response to Request for Additional Information on Preliminary Safety Analysis Report ML16211A0642016-07-21021 July 2016 Us Department of Commerce National Institute of Standards and Technology, Response to Request for Additional Information on Preliminary Safety Analysis Report 2022-08-19
[Table view] |
Text
R. E. Williams J. M. Jurns 05/17/2021 Heat transfer in a disc wedged between two fuel element plates Determine a criterion for re-use of the fuel elements that are offloaded - what is the possible effect of the maximum possible obstruction after restart. What size obstruction (if any) is acceptable in an element and still safe to use that element?
Assumptions Assume an obstruction that is cylindrical in shape, with L defined by the width of the cooling channel between fuel plates in a position where the fuel plate makes the most heat and D varied to determine the overall size and mass of the obstruction (see figure 1).
Consider this for two cases - (1) the obstruction is an aluminum disc, and (2) the obstruction is a disc made entirely of fuel meat.
Heat is conducted into the disc from both circular surfaces directly through the solid contact between fuel plate aluminum cladding and the surface of the cylinder. For the case of a disk of fuel, it is assumed that the disk has the same constituents as NBSR fuel meat, and that heat is generated in the disk at the same rate as the fuel in the adjacent plates.
The cylindrical surface of the inclusion is constantly cooled by the normal coolant flow. The average flow through an element cooled by the outer plenum is 267 GPM (6400 GPM, 24 elements), distributed through 18 coolant channels. For the case of an aluminum obstruction, the disc is heated by a constant 137 W/cm2 from the fuel element. For the case of a fuel meat obstruction, heat is generated from the obstruction itself by a constant 5400 W/cm3, as well as from the fuel element (see figure 2).
Analysis For the case of an aluminum obstruction, the heat into the obstruction equals the 137 W/cm2 multiplied by the area of the disc times two surfaces (assume the disc contacts fuel element on each side of the gap). The heat removed from the obstruction is determined by the heat transfer to the D2O flowing across the cylinder. The disc diameter is increased and obstruction heat in and heat out calculated until the inlet heat exceeds heat being removed. At this point, boiling onset occurs, and obstruction temperature rapidly rises resulting in melting of the obstruction and the fuel element cladding.
For the case of a fuel meat obstruction, the meat itself generates heat as well as the fuel element. The heat generated is 5400 W/cm3. The diameter of the obstruction is increased until the surface temperature of the disk is well above the D2O saturation temperature at which point convection heat transfer is impeded by water vapor resulting in a rapid temperature rise and melting of the obstruction and fuel element cladding.
Results For the case of an aluminum obstruction, a disc 0.295 cm thick and 1.4 cm in diameter (mass = 1.23 g) will result in insufficient heat removed and melting of aluminum obstruction and fuel element cladding.
For the case of a fuel meat obstruction, a disc 0.295 cm thick and 0.2 cm in diameter (mass = 0.03 g) will result in insufficient heat removed and melting of aluminum fuel element cladding.
R. E. Williams J. M. Jurns 05/17/2021 Note that if the obstruction were spherical (not a 0.28 cm thick disc), the equivalent diameter of the smallest obstruction (fuel meat case) is 0.4 cm, which is larger than the width of a channel.
Conclusion It is unlikely that an aluminum obstruction would become wedged in a fuel element gap. It is also unlikely that a spherical fuel meat obstruction would become wedged in a fuel element gap. However, it is possible that a fuel meat disc could become wedged in a fuel element gap as its diameter is less than the gap. These estimates are very conservative in that we assume the obstruction is located at the hot spot in the core, and that any obstruction would likely have an irregular shape with more surface area available for heat transfer to the D2O.
Figure 1.
Figure 2.
R. E. Williams J. M. Jurns 05/17/2021 Heat Transfer in a Disk of Fuel Wedged between Two NBSR Fuel Plates The temperature distribution within a long cylinder with a uniform volumetric heat source is [1]:
T(r) = TS + Sr2/4k (1) where:
S = Volumetric heat source TS = temperature at the outer surface k = thermal conductivity.
Assuming the disk is reconstituted fuel meat (80% Al, 20% U3O8 by volume) wedged between fuel plates at a hot spot we have:
S = 5400 W/cc = 5.4 x 109 W/m3, k = 0.8 x 235 + 0.2 x 0.3 = 188 W/m-K See the attached spreadsheet for calculations.
Heat Transfer in a Disk of Aluminum Wedged between Two NBSR Fuel Plates As aluminum does not generate heat as fuel wedged in a fuel element would, calculated aluminum heat rise can be expressed as:
=
(2)
Where Q is the heat flux x disc area x 2 (heat from both sides):
Heat flux = q = 137 W/cm2 A = *r2disc Heat is removed from the same aluminum obstruction by D2O flowing over it. The heat removed is expressed as:
=
(3)
Where:
=
(4)
=
(5)
Heat removed from the aluminum disc is subtracted from heat input from the fuel element. As aluminum disc diameter increases, so does heat into the disc. When heat into the disc becomes greater than heat removed by the D2O, D2O becomes two phase with a rapid rise in aluminum temperature.
Note that if one calculates an effective equivalent Q per unit volume (as with the fuel meat case), the result from that calculation yields the same resulting aluminum disc diameter - 1.4 cm.
See the attached spreadsheet for calculations.