1. SLAC Measurement Protocols for Unrestricted Release of Metals and Concrete. James Liu, Jim Allan, Sayed Rokni, Amanda Sabourov Radiation Protection Department SLAC National Accelerator Laboratory. DOE Accelerator Safety Workshop, August 17-19, 2010, SLAC, CA.
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James Liu, Jim Allan, Sayed Rokni, Amanda Sabourov
Radiation Protection Department
SLAC National Accelerator Laboratory
DOE Accelerator Safety Workshop,
August 17-19, 2010, SLAC, CA
SLAC measurement protocol for volumetric radioactivity:
Release criterion of IFB (specific activities for natural radioisotopes, e.g., thorium and 40K, are 1-10 pCi/g)
Can also be used for higher release criteria, e.g., EU Clearance Levels, ANSI N13.12 Screening Levels, or DOE Authorized Limits, for release of slightly radioactive materials.
Presented as an example of possible methods and it is not to form the measurement bounding conditions.
SLAC measurement protocol for surface contamination is the same as those commonly used in nuclear facilities, which have detection capabilities satisfying DOE Order 5400.5 Authorized Limits.
Radioisotopes with long half-lives are of interest.
Hard-to-measure radioisotopes (55Fe, 3H), which emit only low-energy X rays or beta rays.
Proxy radioisotopes (22Na, 54Mn, 60Co), which emit high-energy and high-intensity gamma rays
10 Sv/y ANSI N13.12
Screening Level (SL):
22Na, 54Mn, 60Co: 30 pCi/g
55Fe, 3H: 3000 pCi/g (100 Bq/g)
Detection Limit requirement:
∑i (MDAi / SLi) 1
Radioactivity in the BaBar IFR forward steel plug at three decay times
(SA/SL) for 55Fe is much less than (SA/SL) for 60Co
1/1000 in 1-m
55Fe / 22Na 10
1/10 in 1-m
55Fe / 22Na 2
3H / 22Na 2
55Fe / 22Na 10
55Fe / 22Na 2
3H / 22Na 5
10-year irradiation and 5-year decay
Ludlum Model 18 with 44-2 detector
Ludlum Model 2241 with both a 44-2 detector (1” NaI) and a GM pancake
1) ANSI N13.12 SL values were based on 10 Sv/y dose risk
2) ∑i (MDAi / SLi) 1
Detector near Object Surface
Metal with Potential Volumetric Activation
MDA = 4 B / η
Sensitivity [η incpm/(pCi/g)] for various volumetric distributions for proxy radioisotopes in metals were calculated using MCNP
MDA for the uniform case [η= 162 cpm/(pCi/g)] is most conservative
1) ∑i (MDAi / ALi) 1
Graded measurement approach based on process knowledge
General Process Knowledge:
Physics of radioisotope production based on characteristics of accelerator, beam parameters, and materials
Facility-Specific Process Knowledge:
Accelerator and facility operation and beam loss information
Graded Measurement Approach:
Follow MARSSIM and MARSAME guidance
Identification of Areas of Interest (AOIs) or Activities of Interest
Selection of locations of a facility, surfaces of a component, or areas of a surface to be surveyed
Scanning versus discrete point measurements
Samples for Radioanalysis Laboratory measurements
Independent verification when process knowledge is not known, e.g.,
Field gamma spectrometry
Environmental measurement protocol using HPGe with detection limits at least ten times lower than field measurements (0.1 pCi/g for proxy isotopes and 10 pCi/g for 3H)
Surface swipe for 3H and 55Fe LSC analysis
Portal Gate Monitoring:
Detection limits about 1 Ci for proxy isotopes
Useful to supplement the field measurements
Release decisions (e.g., no potential reuse), authorization, and process knowledge, if any (conditions of accelerator, facility and/or materials)
Large items are individually identified, surveyed, and recorded.
Small items are individually surveyed, and collectively identified and recorded.
Instruments, background signals, surveyor, date/time of survey
Photos may be used.
Survey and measurement procedures
Training records for survey technicians
Amounts and types of materials released
Potential Activation in Electron Accelerators Tunnel
Electron Beam Loss
High-Energy and Low-Energy Neutrons
FLUKA is a Monte Carlo code that can calculate induced radioactivity in a 3-D geometry in accelerator facilities, well benchmarked by SLAC and CERN experiments
Notice how the radioactivity profile of each BaBar component has its maximum on the side that faces the source (i.e., e+ and e- collision point inside BaBar)
SALC RP Note 09-04, 2009
Measured Activity Depth Profiles in Concrete
Measurements by Masumoto et al., of KEK at three electron accelerators “Evaluation of radioactivity induced in the accelerator building and its application to decontamination work” in the Journal of Radio-analytical and Nuclear Chemistry, 255:3, 2003.