Radiation Safety Training Session 2: Radiation Protection Systems and Guidelines

Transcription

1 Radiation Safety Training Session 2: Radiation Protection Systems and Guidelines Reading Assignment: LLEINST 6610 Part II, pp. 1 9 Walter T. Shmayda Radiation Safety Officer Laboratory for Laser Energetics University of Rochester

2 Principal radiation sources at LLE facilities Neutron radiation from fusion maximum credible yield shot of neutrons yield 516 rem at the surface of the OMEGA target chamber maximum neutron yield on OMEGA EP is ~10 12 neutrons Gamma radiation from neutron-activated structural components principal sources are Na 24 (15 d) and Mn 54 (213 d) maximum radiation after 10 years not expected to exceed 5 mr/h shortly after a target shot Equipment contaminated by tritium surface contamination airborne releases High-energy x-ray radiation from OMEGA EP fast-electron deceleration in high-z materials prompt radiation activation induced radiation E17573

3 Radiation workers are required to follow standard operating procedures and should consult the RADCON manual Approved standard operating procedures define all key operations living documents: reviewed and optimized referenced during the evolution of any operation emphasis on alertness (non-complacency), understanding the process RADCON manual captures all radiation relevant information for the facility training echoes the chapters of the RADCON manual (sources, protection systems, survey requirements, off-normal responses) provides a variety of survey maps, material entry logs, forms to help standardize and prompt complete reporting living document: updated annually E17574

4 Receipt and disposal of radioactive materials requires Radiation Safety Officer (RSO) approval Receipt verify material type and strength is on our permit arrange through Radiation Safety Unit (RSU) Do NOT transport any radioactive material in personal vehicle Do NOT ship any radioactive materials person-to-person Usage use in approved/properly identified work location secure source in pre-assigned storage facility when not in use All radioactive material/waste is ALWAYS disposed through the RSU. E17846

5 Response to activated materials and radioactive sources depends on the activity level An activated material is defined to be radioactive >0.1 mrem/h on contact tag, log in Radiation Material Log book enter date, activity level, where stored store in pre-approved locations release when activity drops below 0.1 mrem/h on contact Working with activated material >0.1 mrem/h on contact work in pre-approved work space mark work space with Caution Radioactive Material sign mark all entrance ways with Notice to Employees sign E17847

6 Your response to a radiation area is determined by the strength of the source Radiation area: Source 5 mrem/h at 30 cm work in a pre-approved radiation area isolate the area with one entry point post Caution Radiation Area signs around the perimeter RW must be badged controlled access pre-approved work scope limited stay time High radiation area: >100 mrem/h at 30 cm set barrier at 5 mrem/h post a Caution High Radiation Area sign no access to the area E17848

7 Tritium is distributed throughout the Target Chamber and on all components attached to the TC E11598h an

8 Mobile surface contamination is measured by smearing 100 cm2 of a surface and counting the activity collected in the Liquid Scintillation Counter job specific surveys are required when exposed to or handling contaminated materials (TC entry, decontamination activities, maintenance, clearing items ) weekly area surveys are required where tritium is present or handled to verify the cleanliness of the area personnel smears are encouraged when contact with highly active surfaces is suspected (>10 7 DPM/100 cm 2 ) E17577

9 Area and material limits and responses to mobile surface contamination <1000 DPM/100 cm 2 all accessible areas two surveys taken 8 h apart are needed to verify that a component is not contaminated >1000 DPM/100 cm 2 establish Controlled Surface Contamination Areas >10 4 DPM/100 cm 2 pre-defined inaccessible Controlled Surface Contamination Areas examples: TIM s, TC, Moving Cryostat Transport Carts (MCTC s) decontaminate using air purges or pump and vent cycles sample breathable air with portable tritium monitor E17578

10 Ten inch manipulators (TIM) are purged to reduce tritium release when they are opened Swipe Survey Target Debris TC Wall P TC-TRS TM1 Blower Reactor Target chamber Flapper valve Payload door Air purge Air N 2 TIM Vent Other TIMS Aux roughing Purge bypass CMR Recirculation loop H/X Cooler Preheater Recycle valve Drier Low-press receiver E16076a TC-TRS bypass TM2 To stack

11 Controlled surface-contamination areas are used to limit the spread of contamination Establish a Controlled Surface-Contamination Area (CSCA) when the activity of an area or surface >1000 DPM/100 cm 2 work on components with activities >1000 DPM/100 cm 2 is required Establish a barrier and a controlled entry point Post a warning: Controlled Surface Contamination Area Do Not Enter Survey the work area and equipment before clearing the CSCA if >1000 DPM/100 cm 2, clean, re-survey the area 8 hours later For work on components with activities >1000 DPM/100 cm 2 sample airborne activity around the item before transfer install a diffusion cell in the CSCA before the work starts E17849

12 Tritium is a diffuse radiation source. Ventilation and decontamination are the best approaches to reduce dose and cross-contamination Tritium gas (DT, DTO) diffuses from the point of origin to the extremities of a room in a few minutes Surfaces exposed to tritium gas will promptly release DT and then slowly release DTO (and HTO) over an extended period Tritiated water presents a dual hazard DTO vapor and skin absorption of liquid E17579