Summary of phone call between PMT and NEI (March 22, 2011; 9:30AM – 9:48AM)
Ellen Anderson (exa(bnei.org) (leader)
Others (complete list to be emailed by NEI to [email protected])
In response to NEI’s questions on the assumptions the NRC used for the two RASCAL dose assessments that accompanied the March 16, 2011 NRC press release, the PMT provided NEI the following:
The first assessment assumed release from Unit 2. It assumed an ex-vessel, unfiltered release from a totally failed containment, 100% fuel damage, and actual meteorological conditions during early morning hours. The low dispersion characteristics included low wind speeds, relatively stable air, and light precipitation. The assessment considered the conditions of the plant at the time and possible degrading conditions. The assumptions included total failure, sprays off, no removal mechanism (e.g., scrubbing), no mitigation by the operator. A ground level release was assumed with release duration of 16 hours.
The second assessment assumed 30% core damage at Units 2 and 3, and 100% fuel damage for the Unit 4 spent fuel pool. The Unit 4 spent fuel pool was assumed to include only a full core offload from the current outage. To account for the combined inventories of the three units sources (i.e., from Units 2 and 3 and Unit 4 spent fuel pool), the staff adjusted the reactor power level, fuel burnup and number of assemblies, and included that in one calculation. This resulted in 917 assemblies in the core. The
assumptions included total failure, sprays off, no removal mechanism (e.g., scrubbing), no mitigation by the operator. The shutdown time was assumed to be 14:46 hours on March 11, 2011, and the core was assumed uncovered at 19:50 hours on March 16,
2011. This run was modeled as LOCA. In addition, the source term included two additional days of decay before release. For the multi-unit assessment, the increase decay time before release and the greater atmospheric dispersion significantly reduced
the resultant dose estimates. The meteorological conditions for the second assessment also assumed actual conditions with light precipitation, calm wind (between 2 and 5 meters per second) conditions with occasional higher wind speeds (around 10 meters
per second). A ground level release was assumed with a release duration used was 15 hours. For these atmospheric conditions, an average wind speed of 5 meters per second and stability class of “D” would seem a good assumption. Wind direction was primarily from the northwest (NW). The same assessment could easily be used with a wind shift to blow from the northeast (NE). Several other RASCAL runs were done to ensure initial PARs were still valid.
Although the dose projections for the first assessment are somewhat higher than the second assessment, the differences in the modeling assumptions did not affect the overall conclusion that protective action guides would be exceeded beyond fifty miles.
Both assessments are highly speculative, given the lack of actual (representative) site data.
NEI requested to have routine and periodic call to discuss and share with the NRC subsequent dose assessments, but the NRC did not believe that there was a reason for this, particularly due to limited resource and NRC’s focus on the ongoing monitoring and assessment activities. NEI (Ellen Anderson) will email to PMT12.hoc(anrc.gov the names and organizations of the NEI attendees for the call.
Pages From ML12128A335 –4 March 22, 2011 – Summary of Phone Call Between PMT and NEI (930AM – 948AM)