THAM-A - Accelerator Health Physics Orlando IV 10:00 - 11:45
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| Chair(s): Stefania Trovati, Marcia Maria Campos Torres
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THAM-A.1
10:00 Radiation Safety Systems for the LCLS-II Project at SLAC: Use of Beam Loss Monitors to Supplement Shielding SH Rokni*, SLAC National Accelerator Laboratory
Abstract: The Linac Coherent Light Source II (LCLS-II) project at SLAC National Accelerator Laboratory (SLAC) will add a new 4 GeV continuous-wave superconducting (SC) linear accelerator capable of eventually generating up to 1 MHz, 1 MW of average beam power to the existing SLAC Linear accelerator Facility.
LCLS-II will be installed in the existing accelerator housing, parts of which were shielded for lower beam power of few kW. The shielding in such areas will be augmented with a redundant system of fast beam loss monitors inside the shielded enclosure. These monitors will detect beam losses and shut off beams if losses could result in excessive radiation levels in occupied areas, or damaging safety devices such as stoppers, dumps or collimators. The role of active beam loss monitors as part of the overall radiation safety system for the LCLS-II project, design requirements and tests of performance of the systems are presented.
This work was supported by U.S. Department of Energy contract DE-AC02-76SF00515
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THAM-A.2
10:15 Review of RAM Experiments a Graded Approach on Radiological Controls MC Torres*, SLAC
Abstract: SLAC conducts about 50 radioactive experiments (RAM) a year at SSRL. Experiments are categorized in two main categories: Transuranic and other radionuclides which includes Uranium and Technetium as the main isotopes. Radiological controls are applied based on the form of the matrix (e.g. solid, liquid, powder), type of radionuclides and activities of the samples. SLAC is reviewing the existent radiological controls applied to the different samples and is using a graded approach to evaluate if relief from radiological controls can be applied without compromise safety and gain efficiency when providing radiological coverage to the stakeholders.
ACKNOWLEDGEMENTS. This work is supported by Department of Energy Contract DE-AC02-76SF00515
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THAM-A.3
10:30 Radiation Shielding Design of a Cryo-Module Test Facility S Trovati*, SLAC
; M Santana Leitner, SLAC; L Ge, SLAC
Abstract: LCLS-II and its projected upgrade LCLS-II HE will accelerate electron beams at 1 MHz repetition rate in the SLAC Linac. This will be achieved by means of 12-m long cryo-modules, each with 8 super-conducting 9-cell niobium cavities operated at high gradients. These components require extensive testing and optimization prior to installation, or for reconditioning. Thus, for the long term SLAC is considering building an on-site facility with vertical test benches for cavities, a fully-integrated cryomodule test bunker and an RF-gun test stand.
This facility would require shielding and associated controls, as, at high RF gradients, the niobium cavities would emit electrons that would in turn be accelerated, constituting an intense source for radiation. This source has been simulated by means of the Track3P code, while radiation transport on a 3D model of the cryomodule and of the entire facility was evaluated with the FLUKA Monte Carlo code. With this setup, comparisons between future readings of end-cap Faraday cups, radiation monitors, and simulations could be helpful to better understand field emitters in each cryomodule, which can produce high radiation levels.
A preliminary shielding design for this facility is presented.
This work is supported by Department of Energy contract DE-AC02-76SF00515
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THAM-A.4
10:45 Developing Compact Deuterium-Deuterium (DD) Generator Based In Vivo Neutron Activation Analysis (IVNAA) as a New Method for Measuring Sodium (Na) in Bone and Soft Tissue MC Coyne*, Purdue University
; AJ Lobene, Purdue University; CM Weaver, Purdue University; LH Nie, Purdue University
Abstract: Excess dietary sodium (Na) is directly related to hypertension and an increased risk of developing many chronic diseases, but there is currently no method to directly quantify Na retained in the body. Because of this, the locations of Na storage and its exchange mechanisms are not well known. This information is critical for understanding the impact of increased Na intake in modern diets. In order to non-invasively quantify Na in bone and soft tissue, a compact deuterium-deuterium (DD) neutron generator-based based in vivo neutron activation analysis (IVNAA) system was developed. MCNP was used to design a custom irradiation assembly to maximize Na activation in hand bone while minimizing dose. The dose was simulated and measured experimentally with an electronic personal dosimeter (EPD) and neutron and photon meters. For a 10 minute irradiation, the hand receives 47 mSv, which meets the design goal of 10% of the occupational limit. Considering the body weight percentage of the hand, tissue weighting, and including the dose outside of the cavity, the total body dose is estimated to be 27 uSv. In order to test the system, live pigs were used. Two 100% efficient high purity germanium (HPGe) detectors collected Na-24 counts over 24 hours post irradiation. From the pig studies, a two-compartment model of exchange was developed for Na, with an average fast exchange time of 51 minutes and a slow exchange compartment identified, likely to be bone. In the most recent study, baseline IVNAA was performed on two pigs before a 14 day dietary intervention (high and low Na diets). Baseline bone Na was 1395 +/- 87 ppm and 1147 +/- 66 ppm, while post diet bone Na was 1029 +/- 67 ppm and 1153 +/- 67 ppm, for the low and high Na diet pig, respectively. These results show a distinction between the high and low Na pigs and the impact of the diet. With these results, we conclude IVNAA is a useful method to measure Na and is ready for application in human studies.
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THAM-A.5
11:00 Characterization of Measured Activity and Collection Efficiency of Tritium Smears AJ Stavola*, Thomas Jefferson National Accelerator Facility
; AM Hartberger, Thomas Jefferson National Accelerator Facility
Abstract: Tritium particulate collection efficiency varies as a function of smear media. The use of porous smear materials leads to an increase in the measured tritium activity as a function of time when the measurement is performed with liquid scintillation counters. Operational inclusion of the efficiency differences and the time dependence of the tritium smear activity is necessary to preclude inadvertently releasing materials or areas. Thomas Jefferson National Laboratory Radiological Control Department identified a contaminated stainless steel containment vessel which previously housed a target containing more than 1000 Ci of tritium. The item was systematically sectioned and surveyed to compare three smear types: water-wetted cotton swabs, water-wetted paper smears, and ethanol-wetted Styrofoam wipes (NUC-Wipes trademarked). The total activity of each section was determined using repeated decontamination. The time dependence of the measured activity was also studied. The measured activity of both paper smears and cottons swabs showed significant time dependence. The cotton swabs also showed significantly reduced collection efficiency. Given the widespread use of both of these media in routine contamination surveys, site operational limits were derived using fitted curves for time dependence and average efficiency results. The use of these more restrictive limits allows for rapid measurement of tritium smears while ensuring regulatory compliance.
This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177
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THAM-A.6
11:15 Implementation of ALARA Practices for Accelerator Maintenance Work in High Radiation Areas LA Overbay*, Los Alamos National Laboratory
; MA Duran, Los Alamos National Laboratory
Abstract: The Los Alamos Neutron Science Center (LANSCE) is home to an 800 MeV proton accelerator that delivers beam to 5 user facilities (Isotope Production Facility, Lujan Neutron Scattering Center, Weapons Neutron Research (WNR), Ultra Cold Neutron, and Proton Radiography). The Lujan facility uses 100 µA of beam supplied by the Proton Storage Ring (PSR) for its 7 experimental flight paths. PSR extracts beam from the main beamline to “stack” pulses of protons and change the time structure of beam delivery to the Lujan Center. During the 2018 run cycle, there were numerous problems encountered with the PSR equipment resulting in a shutdown of beam delivery to the Lujan Center and impacted beam delivery to WNR facilities when performing maintenance. When repairing the compromised equipment, the Mechanical Design and Engineering (MDE) team entered High Radiation Areas with dose rates between 500-750 mrem/hr in the immediate work area for extended periods of time. This work resulted in increased dose consequences to the MDE team and supporting Radiation Control Technicians. This presentation will discuss the ALARA practices and controls implemented by the Health Physics team to manage both individual and collective doses during the 2018 PSR repair work, as well as what is expected for the upcoming repairs this year.
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