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Title: Simulation of the Post-Shot Radiation Environment in the National Ignition Facility

Abstract

The National Ignition Facility at Lawrence Livermore National Laboratory is the world’s biggest and most energetic laser system for inertial confinement fusion. The NIF is designed to perform shots with varying fusion yield (up to 20 MJ or 7.1 × 10 18 neutrons per shot). A great number of diagnostic instruments are present inside the target chamber (TC) and target bay (TB) during shots. The gamma dose rates due to neutron activation are estimated at various decay times following the high-yield (20-MJ) shots. Several components, like the snout assemblies of the diagnostic instrument manipulators and target positioners are inserted inside the TC, close to the target during the shot. These components represent major sources of gamma decay after retraction outside the TC. Five days after a 20-MJ shot, dose rates near the highly activated (retracted) parts are on the order of 1 mSv/h and dose rates within the TB outside the TC but at distance from the retracted components drop to about 50 to 70 μSv/h. The dose is dominated by decay of 24Na (T 1/2 = 14.95 h) and waiting for two additional days drops the dose rates significantly. Seven days following a 20-MJ shot, dose rates in themore » immediate vicinity of the retracted components drop to <0.2 mSv/h and the general ambient dose rates within the TB (away from retracted components) near the TC drop to <10 μSv/h. Dose rates at much larger distances from the TC (near TB wall) are an order of magnitude lower. Detailed radiation transport simulations are performed to create detailed dose rate maps for all floors inside the TB. The maps are used to measure worker stay-out times following shots before entry is permitted into the TB.« less

Authors:
 [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1]
  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1557056
Report Number(s):
LLNL-JRNL-746277
Journal ID: ISSN 1536-1055; 930635
Grant/Contract Number:  
AC52-07NA27344
Resource Type:
Accepted Manuscript
Journal Name:
Fusion Science and Technology
Additional Journal Information:
Journal Volume: 74; Journal Issue: 4; Journal ID: ISSN 1536-1055
Publisher:
American Nuclear Society
Country of Publication:
United States
Language:
English
Subject:
61 RADIATION PROTECTION AND DOSIMETRY; National Ignition Facility; post-shot dose; neutronics; Monte Carlo

Citation Formats

Khater, Hesham, Brereton, Sandra, Dauffy, Lucile, Hall, Jim, Hansen, Luisa, Kim, Soon, Pohl, Bertram, Sitaraman, Shiva, Verbeke, Jerome, and Young, Mitchell. Simulation of the Post-Shot Radiation Environment in the National Ignition Facility. United States: N. p., 2018. Web. doi:10.1080/15361055.2018.1471961.
Khater, Hesham, Brereton, Sandra, Dauffy, Lucile, Hall, Jim, Hansen, Luisa, Kim, Soon, Pohl, Bertram, Sitaraman, Shiva, Verbeke, Jerome, & Young, Mitchell. Simulation of the Post-Shot Radiation Environment in the National Ignition Facility. United States. doi:10.1080/15361055.2018.1471961.
Khater, Hesham, Brereton, Sandra, Dauffy, Lucile, Hall, Jim, Hansen, Luisa, Kim, Soon, Pohl, Bertram, Sitaraman, Shiva, Verbeke, Jerome, and Young, Mitchell. Fri . "Simulation of the Post-Shot Radiation Environment in the National Ignition Facility". United States. doi:10.1080/15361055.2018.1471961. https://www.osti.gov/servlets/purl/1557056.
@article{osti_1557056,
title = {Simulation of the Post-Shot Radiation Environment in the National Ignition Facility},
author = {Khater, Hesham and Brereton, Sandra and Dauffy, Lucile and Hall, Jim and Hansen, Luisa and Kim, Soon and Pohl, Bertram and Sitaraman, Shiva and Verbeke, Jerome and Young, Mitchell},
abstractNote = {The National Ignition Facility at Lawrence Livermore National Laboratory is the world’s biggest and most energetic laser system for inertial confinement fusion. The NIF is designed to perform shots with varying fusion yield (up to 20 MJ or 7.1 × 1018 neutrons per shot). A great number of diagnostic instruments are present inside the target chamber (TC) and target bay (TB) during shots. The gamma dose rates due to neutron activation are estimated at various decay times following the high-yield (20-MJ) shots. Several components, like the snout assemblies of the diagnostic instrument manipulators and target positioners are inserted inside the TC, close to the target during the shot. These components represent major sources of gamma decay after retraction outside the TC. Five days after a 20-MJ shot, dose rates near the highly activated (retracted) parts are on the order of 1 mSv/h and dose rates within the TB outside the TC but at distance from the retracted components drop to about 50 to 70 μSv/h. The dose is dominated by decay of 24Na (T1/2 = 14.95 h) and waiting for two additional days drops the dose rates significantly. Seven days following a 20-MJ shot, dose rates in the immediate vicinity of the retracted components drop to <0.2 mSv/h and the general ambient dose rates within the TB (away from retracted components) near the TC drop to <10 μSv/h. Dose rates at much larger distances from the TC (near TB wall) are an order of magnitude lower. Detailed radiation transport simulations are performed to create detailed dose rate maps for all floors inside the TB. The maps are used to measure worker stay-out times following shots before entry is permitted into the TB.},
doi = {10.1080/15361055.2018.1471961},
journal = {Fusion Science and Technology},
number = 4,
volume = 74,
place = {United States},
year = {2018},
month = {6}
}

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Works referenced in this record:

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