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Title: Analysis of activated air following high yield shots in the NIF

During the ignition experimental campaign, the National Ignition Facility (NIF) is expected to perform shots with varying fusion yield (up to 20 MJ or 7.1 x 10 18 neutrons per shot) and a maximum annual yield of 1200 MJ. A detailed MCNP model of the Target Bay (TB) and the two switchyards (SY) has been developed to estimate the post-shot radiation environment inside the facility. During D-T shots, a pulse of 14.1 MeV neutrons streaming outside the Target Chamber (TC) will activate the air present inside the TB and the argon gas inside the laser tubes. Smaller levels of activity are also generated in the SY air and in the argon portion of the SY laser beam path. The activated TB air will be mixed with fresh air from the Operations Support Building (OSB) before release through the stack. Flow of activated air from the Target Bay is controlled by the heating, ventilating, and air conditioning (HVAC) system. 16N (T 1/2 = 7.13 s) dominates the radiation levels during the first minute following the shot. It is expected that 16N will decay away during the confinement time before releasing the TB air through the stack. The other major contributors aremore » 13N (T 1/2 = 9.97 min) and 41Ar (T 1/2 = 1.83 h). In general a low dose rate of < 1 μSv/h is expected near the stack during the first few hours following a 20 MJ shot. Here, the amount of activated Target Bay air released through the stack is very small and does not pose significant hazard to personnel or the environment. In the mean time, due to a very small leakage rate out of the laser tubes, the activated argon gas decays within the tubes and any resulting release to the environment is insignificant.« less
Authors:
 [1] ;  [1]
  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Publication Date:
Report Number(s):
LLNL-JRNL-665140
Journal ID: ISSN 1536-1055
Grant/Contract Number:
AC52-07NA27344
Type:
Accepted Manuscript
Journal Name:
Fusion Science and Technology
Additional Journal Information:
Journal Volume: 68; Journal Issue: 3; Journal ID: ISSN 1536-1055
Publisher:
American Nuclear Society
Research Org:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
61 RADIATION PROTECTION AND DOCIMETRY
OSTI Identifier:
1342063