ML24289A186

Clarification Questions on Fort Calhoun Station Phase 1 Final Status Survey Report Request for Additional Information Responses

ML24289A186
Person / Time
Site:	Fort Calhoun
Issue date:	10/09/2024
From:	Jack Parrott Reactor Decommissioning Branch
To:	Pearson B Omaha Public Power District
References
Download: ML24289A186 (1)

Text

1 Clarification Call Comments/Questions FCS Phase 1 FSSR RAI Responses RAI-01-01 RAI-01-01 requested that instrument and sample analysis minimum detectable concentrations calculated for comparison with the DCGLs be explicitly stated in the SURRs, including calculations for a posteriori MDC.

A) Response (1)(a) indicates that the scan MDC for the 44-20 was calculated by using the TSD for the 44-10 and substituting the correct CPMR for a 44-20 with an assumed 100%

Cs-137 radionuclide mix. The ERC is discussed in the paragraph below and the value chosen was taken from the 44-10 TSD with an assumed radionuclide mix of 95% Cs-137 and 5% Co-60. The fraction used in FC-19-006 is 90% Cs-137 and 10% Co-60 allowing for some variability. Table 5-3 of the LTP applies the mixture fraction for the AB/TB/RWPB for soils. In addition, Eu-152 is considered in FSS planning. Explain the use of a 95% Cs-137 and 5% Co-60 fractions given the difference in site data.

1) The response, which a given background of 76,000 cpm appear to be a priori MDC. The background range for all survey units in the Phase I submittal range from 18,087 cpm to 36,880 cpm. Explain the use of a background rate of 76,000 cpm, particularly in the case where the background range is significantly below this value.

2) In response (1)(a), a d value of 1.38 was given corresponding with a true positive of 95% and a false positive of 60%. Explain the selection of an index of sensitivity of 1.38 based on site-specific considerations. Note that the confirmatory surveys utilize a d value of 2.32, which corresponds to a false positive value of 0.25 and the acceptable probability of a detection at 95%.

B) Response (2) states that a TSD specifically for the Ludlum 44-20 is in preparation. What additional information not currently in the RAI response will be included in the 44-20 TSD? When would this TSD be submitted for review?

RAI-01-06 A) Response (a) states that if no samples were taken in an SU, relative shift was calculated using general survey area characterization data. If samples were taken in a specific SU during this characterization, that subset of samples was used to calculate relative shift.

1) While Table 3-1 of the various SURRs reflect this (or appear to), the calculated relative shift for those SUs using Survey Area data versus those SUs using Survey Unit Specific data are the same. Explain why this is?

2) Note that sample statistics and relative shift were calculated using both random +

judgmental samples...should be calculated using just random samples.

2 B) Response (b) states the licensee plans to provide a description of the survey unit specific relative shifts and the characterization samples used for the calculation of the relative shifts in a revision to the SURR. Additionally, Eu-152 data will be added to Table 3-1, to facilitate the reproducibility of the relative shift from the data contained within each SURR.

1) When do you expect to submit an updated version of the SURR with this data? If a significant delay is expected, in the interim, please provide a spreadsheet containing the results of the samples used to calculate the summary statistics in Table 3-1 for survey units 8101, 8106, 8202, and 8305 similar to that included in Table 2-48 of the LTP. Alternatively, for 8101, 8202, and 8305 point to the specific data in Chapter 2 of the LTP used for these calculations.

C) Response (c) acknowledges that the LBGR is set as the mean of the characterization data set expressed as an SOF and the standard deviation as the weighted standard deviation of the characterization data set.

1) While 8101, 8103, 8104, 8105, 8109, and 8110 used different data sets with differing means and standard deviations, Equation 5-1 for these survey units applies the same mean and standard deviation. A similar situation occurs with 8202 and 8203, and 8305 and 8307. Differing data sets should not yield identical values. Please explain why this is the case.

The staff also notes that the licensee proposes the following revisions to the Phase I SURRs.

a. Addition of instrument and ISOCS MDCs directly comparable to the DCGLs.

b. Addition of onsite and offsite laboratory sensitivities.

c. Inclusion of a statement on how the ISOCS was applied in open land area surveys.

d. Modification of the SOF to remove ISOCS measurements.

e. Addition of the descriptions of the survey unit specific unit specific relative shifts and the characterization samples used for the calculation.

f. Addition of Eu-152 data to Table 3-1, to facilitate the reproducibility of the relative shift.

g. Figures will be provided in the SURRs to accurately display all scan areas and the location of random samples within each unit.

h. Clarity and consistency will be provided for scan area designations in Table 7-1 of the SURRs.

i.

Correction of inconsistencies in the maximum OpSOF between the executive summary and Table 7-4 for Survey Units 8103 and 8109.

j.

Correction of background measurement heights for the NaI detector for Survey Units 8103 and 8106.

Will these revisions be submitted with the SURR update?