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Significant Sensitivities in Developing Radiological Dose Consequences When Using MACCS2

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Significant Sensitivities in Developing Radiological Dose Consequences When Using MACCS2

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    1. Significant Sensitivities in Developing Radiological Dose Consequences When Using MACCS2 20th Annual EFCOG Safety Analysis Workshop April 28th 2010 Kevin Brotherton, EIT Nuclear Safety Consultant Kevin.Brotherton@WSMS.com Ms. Stephanie Aceto & Dr. Dave Thoman

    2. Objective #1 – Show the effect of using DOE-STD-1189-2008 c/Q value instead of c/Q values determined by site specific meteorological data in regards to the 100 meter worker dose consequence Objective #2 – Show the effect of dry deposition on the dose consequence to the 100 meter worker Objective #3 – Show the effect of changing MACCS2 grid locations for the 100 meter worker in regards to dose consequence Points of Interest

    3. Objective #1 – Show the effect of using DOE-STD-1189-2008 c/Q value instead of c/Q values determined by site specific meteorological data in regards to the 100 meter worker dose consequence Objective #2 – Show the effect of dry deposition on the dose consequence to the 100 meter worker Objective #3 – Show the effect of changing MACCS2 grid locations for the 100 meter worker in regards to dose consequence Objective #1

    4. Objective #1 – DOE-STD-1189-2008 General Information Approved March 2008 Integration of Safety into the Design Process Appendix A – Safety System Design Criteria Prescribed c/Q value to be used for dispersion calculations regarding the co-located worker c/Q value to be used is 3.5E-03 sec/m3

    5. Objective #1 – DOE-STD-1189-2008 c/Q Specifics 100 Meter Receptor Location F Stability Class No Buoyancy 1.0 m/sec Wind Speed at 100 Meters 1.0 cm/sec Deposition Velocity Small Building Size – 10 Meters x 25 Meters Does NOT account for ground shine Does NOT account for cloud shine Does NOT have a specific release duration

    6. Objective #1 – Site Specific Meteorological Data Analyzed Idaho National Lab – INL 2005 95th Percentile Los Alamos National Lab – LANL 2003 – 2007 95th Percentile Lawrence Livermore National Lab – LLNL 1999 90th Percentile Oak Ridge National Lab – ORNL 1996 – 1998 90th Percentile Sandia National Lab – SNL 2002 – 2004 95th Percentile

    7. Objective #1 Site Specific Meteorological Data Analyzed Savannah River National Lab – SRS 1997 – 2006 95th Percentile Waste Isolation Pilot Plant – WIPP 2004 95th Percentile Waste Treatment Plant - Hanford 2002 – 2007 95th Percentile

    8. Objective #1 Results – 3 Minute Release Duration c/Q Values

    9. Objective #1 Results – Percentage Decrease in Co-Located Worker c/Q for 3 Minute Release

    10. Objective #1 Results – 20 Minute Release Duration c/Q Values

    11. Objective #1 Results – Percentage Decrease in Co-Located Worker c/Q for 20 Minute Release

    12. Objective #1 Results – 1 Hour Release Duration c/Q Values

    13. Objective #1 Results – Percentage Decrease in Co-Located Worker c/Q for 1Hour Release

    14. Objective #1 Results – 8 Hour Release Duration c/Q Values

    15. Objective #1 Results – Percentage Decrease in Co-Located Worker Dose for 8 Hour Release

    16. Objective #1 Results Summarized Using the prescribed c/Q value from DOE-STD-1189-2008 can increase the co-located worker c/Q by up to 270% (SRS – 8 Hour Release Duration) Using the prescribed c/Q value from DOE-STD-1189-2008 can decrease the co-located worker c/Q by up to 79% (LLNL – 3 Minute Release Duration)

    17. Objective #1 – Important Things to Consider DOE-STD-1189-2008 c/Q value does NOT include cloud shine and ground shine Isotopes such as Cs-137/Ba-137m can have 20% to 30% of their dose due to shine, how should these be treated?

    18. Objective #1 – Important Things to Consider DOE-STD-1189-2008 c/Q value only has one associated release duration Should events such as an explosion have the same release duration as spills? ARR are to be multiplied by release duration, should resuspension use a c/Q value associated with one release duration and then use a different release duration when applying the ARR? Release duration associated with DOE-STD-1189-2008 c/Q value is 30 minutes based on NUREG 1140

    19. Objective #1 – Show the effect of using DOE-STD-1189-2008 c/Q value instead of c/Q values determined by site specific meteorological data in regards to the 100 meter worker dose consequence Objective #2 – Show the effect of dry deposition on the dose consequence to the 100 meter worker Objective #3 – Show the effect of changing MACCS2 grid locations for the 100 meter worker in regards to dose consequence Objective #2

    20. Objective #2 – Deposition General Information Dry Deposition The deposition (removal) of particles from the atmosphere via particles sticking to surfaces during plume transport The rate of deposition is directly linked to the deposition velocity. The deposition velocity gives a rate at which the particles fall to the ground.

    21. Objective #2 – Deposition General Information Deposition velocity is defined as V=F/C V – Deposition Velocity [cm/sec] F – Flux Density [gm/cm2sec] C – Concentration [gm/cm3] Generally, a value of 1.0 cm/sec is used for unmitigated unfiltered? accidents (2-5 micron larger particle size) Generally, a value of 0.1cm/sec is used for mitigated (filtered) accidents (.2 to .4 micron smaller particle size)

    22. Objective #2 – Experiment Specifics Pu-238 1 Becquerel Release Ground Level Release Meteorological Data SRS 1997 – 2001 95th Percentile Release Duration 3 Minute 20 Minute 1 Hour

    23. Objective #2 – Experiment Specifics Surface Roughness 3 centimeter 100 centimeter Dispersion Parameters Tadmor-Gur Power Law Fit Dry Deposition Amount Determination Comparing the c/Q value in MACCS2 output to the centerline air concentration (c/Q value including deposition)

    24. Objective #2 Results – 3 Minute Release Percentage Decrease in c/Q

    25. Objective #2 Results – 20 Minute Release Percentage Decrease in c/Q

    26. Objective #2 Results – 1 Hour Release Percentage Decrease in c/Q

    27. Objective #2 Results – Release Duration Based Percentage Decrease in c/Q

    28. Objective #2 – Conclusion The effect of dry deposition on the co-located worker was generally less than 10% decrease in dose for events using a 3 cm surface roughness. For MACCS the deposition is proportional to the surface level concentration which is higher for lower surface roughness lengths for ground level releases The effect of dry deposition on the co-located worker was generally less than 5% decrease in dose for events using a 100 cm surface roughness. The surface roughness of an event appears to have a direct effect on the decrease in dose due to deposition.

    29. Objective #2 – Conclusion The release duration does not appear to have a significant effect on the decrease in dose due to deposition. Given the results of these experiments and that the decreases in dose are within the uncertainty of the MACCS2 software which is +/- (10%).

    30. Objective #1 – Show the effect of using DOE-STD-1189-2008 c/Q value instead of c/Q values determined by site specific meteorological data in regards to the 100 meter worker dose consequence Objective #2 – Show the effect of dry deposition on the dose consequence to the 100 meter worker Objective #3 – Show the effect of changing MACCS2 grid locations for the 100 meter worker in regards to dose consequence Objective #3

    31. Objective #3 – General Information When preparing for a MACCS2 run, there are several files that are created DCF Early Atmos Within the Atmos file there are specific grid locations where measurements are to be taken When requesting a certain grid location for output, the location given is the midpoint between two of the grid locations

    32. Objective #3 – General Information If one were to want the 100 meter dose, then the dose requested would be 0.20

    33. Objective #3 – Experiment Specifics Pu-238 1 Becquerel Release Ground Level Release Meteorological Data SRS 1997 – 2001 90th, 95th, and 99th Percentile 95th Release Duration 3 Minute 20 Minute 1 Hour 8 Hour

    34. Objective #3 – Experiment Specifics Surface Roughness 3 centimeter 100 centimeter Dispersion Parameters Tadmor-Gur Power Law Fit Grid Locations 0.00 and 0.20 to obtain 100 meter c/Q 0.05 and 0.15 to obtain 100 meter c/Q

    35. Objective #3 – Experimental Specifics The grid locations have changed to narrow the gap between.

    36. Objective #3 – 3 Minute Release Percentage Decrease in c/Q

    37. Objective #3 – 20 Minute Release Percentage Decrease in c/Q

    38. Objective #3 – 1 Hour Release Percentage Decrease in c/Q

    39. Objective #3 – 8 Hour Release Percentage Decrease in c/Q

    40. Objective #3 – Summarized Results Changing the MACCS2 grid locations can decrease the co-located c/Q value by up to 33.51% 99th Percentile 100 cm Surface Roughness 1999 SRS Meteorological Data 8 Hour Release Duration

    41. Objective #3 – Summarized Results Changing the MACCS2 grid locations can decrease the co-located c/Q value by as little as 13.30% 95th Percentile 100 cm Surface Roughness 1999 SRS Meteorological Data 20 Minute Release Duration

    42. Concluding Remarks Special Thanks Ms. Stephanie Aceto WSMS Assisted in running MANY MACCS2 runs in preparation for this presentation Dr. Dave Thoman WSMS MACCS2 SME Personal Accident Analysis Mentor for 3+ Years WSMS Sandia National Lab

    43. Questions

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