Deposition Velocity Issues at Y-12

Bruce A WilsonChief Engineer, Nuclear Facility Safety

Douglas ClarkAnalyst

B&W Technical Services Y-12

May 9, 2012

Deposition Velocity Issues at Y-12

Brief History & Timeline

• 2007/2008 DNFSB issues with ARF and Dispersion Modeling Codes

• May 2008, agreed upon MACCS2 with DV = 1 cm/s, issued response to Board

• WTP letter on DV issued– B&W prepares tech. basis for DV

• May 2011 - HSS safety bulletin issued– B&W revises tech. basis to

address all items in safety bulletin

• Currently in continuing dialogue on technical basis.

Deposition Velocity Issues at Y-12

Response Letter

• Included specification of every parameter to be used in dispersion modeling for UPF and consequence analysis for new and existing facilities at Y-12

Deposition Velocity Issues at Y-12

Attachment to Response Letter

Deposition Velocity Issues at Y-12

Use and Presentations on DV

• DV=1.0 cm/sec used on “parking lot” fires for UPF

• Used in first annual update of HEUMF along with MACCS2 and POSTMAX

• Presentation by Megan Houchin at November 2010 SAWG meeting– Followed DNFSB staff report on DV at Hanford– Concluded dose would increase by 4.75 from DV=0.0 to

DV=1.0 but does NOT change safety classification of controls.

Deposition Velocity Issues at Y-12

HSS Bulletin and Aftermath

• HSS Bulletin issued in May 2011

• Y-12 Design Analysis Calculation (DAC) also issued in May 2011

• DAC was revised in September 2011 to more completely address HSS bulletin– Added DV calculations based on GENII2

• Again revised in November 2011 to address HSS and CDNS comments

• Conclusion remained: “Taking into account Y-12 site specific conditions, all calculated DVs exceed 1 cm/s.”

Deposition Velocity Issues at Y-12

Rev. 2 of the Deposition Velocity Calculation

• Discussion of calm wind conditions

• Includes particle size analysis and detailed basis for each parameter

• Uses 5 years of site-specific meteorological data

Deposition Velocity Issues at Y-12

Calm Wind Conditions At Y-12

Deposition Velocity Issues at Y-12

Surface Roughness Estimates for DV only

• Used AERSURFACE program (Rev. 2 used annual averages)

• Neglected topographical roughness

Deposition Velocity Issues at Y-12

Information provided to DNFSB since November 2011 meeting

Dispersion Analysis (MACCS2 and Deposition Velocity): Agenda DV- Telecon Agenda – UPF dispersion Parameter Telecon DAC-F000Y12-F-0005, “Technical Basis for Atmospheric Dispersion using MACCS2 DAC-FS-900000-A033, Draft Appendix B, “Determination of Atmospheric Stability Category” Diabatic Wind Profile Under Calm Conditions, White Paper MACCS2 input files Single Slide for DV-Sensitivity.pptx Spreadsheet entitled “UPF-DV-Simplified(GENII2)-Rev2.xls Surface Roughness – AERSURFACE OUTPUT FILE WP-PM-801768-A001, Comparison of Modules and Recommendations for Wake Effects and

Surface Roughness Coefficients in the MACCS2 and HGSYSTEM/WAKE Atmospheric Transport and Dispersion Models

Meteorology: EMPO-556, “Oak Ridge Y-12 National Security Complex Meteorology Monitoring System Pictures of Y-12 West Tower Proposed DNFSB Staff Teleconference Agenda Y-12 Meteorology Data – Responses

Other Issues: DAC-FS-900000-A024, “Impact Analysis of Revised Consequence Modeling Parameters (U)”

Deposition Velocity Issues at Y-12

DV Feeds into Parametric Dispersion Analysis

Deposition Velocity Issues at Y-12

Parametric Evaluation of Dispersion at Y-12

Deposition Velocity Issues at Y-12

Parametric Evaluation Range

Deposition Velocity Issues at Y-12

Parametric Evaluation Recommendations

Deposition Velocity Issues at Y-12

Deposition Velocity Issues at Y-12

Current Status (conclusion)

• DNFSB letter of April 2, 2012 identified: – “(5) the need to use reasonably conservative values

to calculate dose consequences for several accident analyses that may require safety class controls.”

• DNFSB report states that the dry deposition calculation is compliant with the HSS Bulletin but uses non-conservative parameters.

• Meeting with DNFSB on May 7, 2012 to present 30 day response to letter.

Deposition Velocity Issues at Y-12

Disclaimer

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