In this report, the inventory is updated to account for the decay of radionuclides over two additional decades (1992-2012) and revised tritium, fission product and actinide inventory figures and tables are presented. In that original report, the underground radionuclide inventory at the Nevada National Security Site (NNSS) was decay corrected to September 23, 1992, the date of the last underground nuclear test at the NNSS. This report is an update of report LA-13859-MS (Bowen et al., 2001). Portal monitor count rates corresponding to a committed effective dose E(50) of 10 mSv are reported. The time-dependant organ concentrations of the radionuclides were determined using Dose and Risk Calculation Software Eckerman, Leggett, Cristy, Nelson, Ryman, Sjoreen and Ward (Dose and Risk Calculation Software Ver. The count rates of the portal monitor were simulated for inhalation and ingestion of likely radionuclides from an RDD for each of the phantoms. A model of the portal monitor was created for use with models of six anthropomorphic phantoms in Monte Carlo N-Particle Transport Code Version 5 (MCNP) X-5 Monte Carlo Team (MCNP A General more » Monte Carlo N-Particle Transport Code Version 5. This study evaluated the suitability of a radiation portal monitor for such screening. Since the current laboratory capacity to screen for internal contamination is limited, rapid field screening methods can be useful in prioritizing individuals. « lessįollowing a radioactive dispersal device (RDD) incident, it may be necessary to evaluate the internal contamination levels of a large number of potentially affected individuals to determine if immediate medical follow-up is necessary. However, the intent is to plot the critical mass data along with USL, not to suggest that already accepted handbook data should have new and more rigorous requirements for validation. This paper attempts to take a novel approach to visualize traditional critical mass curves and allows comparison with the amount of mass for which the k eff is equal to the USL (calculational margin + margin of subcriticality). ANSI/ANS-8.1 states that it is acceptable to use handbook data, such as the data directly from the LA-10860-MS, as it is already considered validated (Section 4.3 4) “Use of subcritical limit data provided in ANSI/ANS standards or accepted reference publications does not require further validation.”). The USL was then used to determine the equivalent mass for plutonium metal-water system. The baseline USL for each of the data points of the curves was then computed using Whisper 1.1. A series of critical mass curves for plutonium, similar to those found in Figure 31 of LA-10860-MS, have been generated using MCNP6.1.1 and the iterative parameter study software, WORM_Solver. The combination of the Whisper-derived calculational margin and MOS comprise the baseline upper subcritical limit (USL), to which more » an additional margin may be applied by the nuclear criticality safety analyst as appropriate to ensure subcriticality. Whisper attempts to quantify the margin of subcriticality (MOS) from errors in software and uncertainties in nuclear data. Using these benchmarks, Whisper computes a calculational margin. Whisper uses sensitivity/uncertainty (S/U) methods to select relevant benchmarks to a particular application or set of applications being analyzed. Standard approaches to validation rely on the selection of benchmarks based upon expert judgment. Whisper is computational software designed to assist the nuclear criticality safety analyst with validation studies with the MCNP ® Monte Carlo radiation transport package.
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