1. SHIELDING for a HIGH ENERGY DIGITAL RADIOGRAPHY BAY P.Berry, P. Heintz, S.K.Velarde Los Alamos National Laboratory University of New Mexico Medical School Three Rivers Technical Conference 2010 Rogers, MN Unclassified per T. N. Claytor, ADC 3/15/10

2. WERE GOING HIGH ENERGY

3. OBJECTIVES OBJECTIVES Identify key personnel needed to build a radiography facility Identify key personnel needed to build a radiography facility Know the elements and requirements in the building Know the elements and requirements in the building Know the basic elements in performing shielding calculations Know the basic elements in performing shielding calculations Follow the project after the planning phase through completion Follow the project after the planning phase through completion

4. PLANNING COMMITTEE PLANNING COMMITTEE Management Representative (budget) Management Representative (budget) Radiographers Levels II and III Radiographers Levels II and III Radiological Physicist Radiological Physicist Architect Architect Construction Representative Construction Representative Equipment Vendor Equipment Vendor

5. KEY to SUCCESS KEY to SUCCESS COMMUNICATION COMMUNICATION And perhaps cooperation and consensus

6. Some Issues to be Addressed What accelerator to purchase? What accelerator to purchase? What objects will be radiographed? What objects will be radiographed? What modalities will be used (DR,CT)? What modalities will be used (DR,CT)? Any other activities in the facility? Any other activities in the facility? Types of doors (sliding or swinging)? Types of doors (sliding or swinging)? Handling and storing of radioactive material? Handling and storing of radioactive material? Future use of area around the facility? Future use of area around the facility?

9. Some Issues to be Addressed Some Issues to be Addressed Density of the concrete has to be specified Density of the concrete has to be specified Mechanical penetrations have to be planned in advance Mechanical penetrations have to be planned in advance Plan for HVAC Plan for HVAC If any changes are made to the original plan NOTIFY the physicist IMMEDIATELY If any changes are made to the original plan NOTIFY the physicist IMMEDIATELY Ensue proper concrete pouring techniques Ensue proper concrete pouring techniques

10. door D-primary D-leakage

11. Description of the Environment Outside of the Bay Parking Lot to the left of the bay. Parking Lot to the left of the bay. Grassy area in the direction of the primary beam Grassy area in the direction of the primary beam New office building will be constructed 100 ft in the direction of the primary beam. New office building will be constructed 100 ft in the direction of the primary beam. Radiography bay will be inside of a larger building. Radiography bay will be inside of a larger building. 8 foot wide hallway separating the bay and office space. 8 foot wide hallway separating the bay and office space.

12. PRODUCTION OF RADIATION TYPES IN A LINAC electrons photons BREMSSTRAHLUNG Photo-neutrons production Radioactive nucleus Pair-production positron electron Radioactive nucleus Neutron capture ACCELERATOR HEAD > 10 MeV

13. Photoneutron Production Photoneutron Production Interaction of photon beam with heavy metal accelerator components results in neutron production. Interaction of photon beam with heavy metal accelerator components results in neutron production. For all practical purposes neutron production threshold is 8-10 MeV. For all practical purposes neutron production threshold is 8-10 MeV. Neutrons are emitted isotropically and scattered many times Neutrons are emitted isotropically and scattered many times Photoneutrons are produced mainly from the target, and collimators– exiting through the collimator Photoneutrons are produced mainly from the target, and collimators– exiting through the collimator

14. Threshold for Photoneutron Production Threshold for Photoneutron ProductionElement Atomic Number (A) (A) Abundance (%) Threshold Energy (MeV) D 2.02.02 2.23 2.23 Be Be 9 100 100 1.67 1.67 Cu Cu 63 63 69.2 69.2 10.85 10.85 Cu Cu 65 65 30.8 30.8 9.91 9.91 W 182 182 26.3 26.3 8.06 8.06 W 184 184 30.6 30.6 7.41 7.41 Pb Pb 208 208 52.4 52.4 7.37 7.37

15. Definitions Definitions Control Area: limited access area with the occupational exposure controlled by the radiation supervisor Control Area: limited access area with the occupational exposure controlled by the radiation supervisor Uncontrolled area: any space not meeting the definition of a controlled area (general public) Uncontrolled area: any space not meeting the definition of a controlled area (general public) Shielding design goals (P): effective dose values recommended by NCRP-2004 for controlled and uncontrolled areas Shielding design goals (P): effective dose values recommended by NCRP-2004 for controlled and uncontrolled areas Primary Barrier: a wall, ceiling, or floor designed to attenuate the useful beam to the required degree Primary Barrier: a wall, ceiling, or floor designed to attenuate the useful beam to the required degree Primary radiation: radiation emitted directly from the source that is intended to be used for industrial imaging Primary radiation: radiation emitted directly from the source that is intended to be used for industrial imaging

16. Definitions Definitions Occupancy factor (T): the fraction of time that the maximally exposed person is present in an area while the beam is on. (always 1.0 for radiation workers) Occupancy factor (T): the fraction of time that the maximally exposed person is present in an area while the beam is on. (always 1.0 for radiation workers) Workload (W): the average dose of radiation produced by a source over a specified time (most often a week) at a specific location. If there is no dependable information, assume 8 hours per day, 5 days a week for a total of 40 hours per week. If this is to be exceeded, NCRP 51 page 42 gives the guidelines for this problem. Workload (W): the average dose of radiation produced by a source over a specified time (most often a week) at a specific location. If there is no dependable information, assume 8 hours per day, 5 days a week for a total of 40 hours per week. If this is to be exceeded, NCRP 51 page 42 gives the guidelines for this problem.

17. Definitions Definitions Secondary Barrier: A wall, ceiling, floor designed to attenuate leakage and scattered radiation to the required goal. Secondary Barrier: A wall, ceiling, floor designed to attenuate leakage and scattered radiation to the required goal. Secondary radiation: All radiation produced by scattering off of objects, or leakage through the protective source housing –all radiation in the bay except for the primary beam Secondary radiation: All radiation produced by scattering off of objects, or leakage through the protective source housing –all radiation in the bay except for the primary beam Leakage radiation: All radiation, except the useful beam, coming from within the accelerator head and other beam-line components. Leakage radiation: All radiation, except the useful beam, coming from within the accelerator head and other beam-line components. Use factor (U): the fraction of a primary beam workload that is directed toward a primary barrier Use factor (U): the fraction of a primary beam workload that is directed toward a primary barrier

18. Shielding Design Goals Shielding Design Goals Controlled Area 0.1 mGy/wk Controlled Area 0.1 mGy/wk Uncontrolled Area 0.02 mGy/wk Uncontrolled Area 0.02 mGy/wk

19. Shielding Materials Shielding Materials MaterialDensity(g/cm^3)RadiationTypeAdvantageDisadvantage Concrete2.35 Photons & NeutronsInexpensive Requires too Much space High Density Concrete3.8-4.6 Photons & Neutrons Gain space Expensive Earth1.4-1.6 Photons & Neutrons Almost Free Difficult to control Boratedpolyethylene0.95Neutrons High cross Section for Thermal n. Expensive Lead11.35Photons Save space Produce neutrons Steel7.9Photons Save space Produce neutrons

20. Assumptions for the Problem 15 MV LINAC 15 MV LINAC Dose Rate 20,000 cGy/min@ 1 meter (200 Gy/min) Dose Rate 20,000 cGy/min@ 1 meter (200 Gy/min) Leakage.001% Leakage.001% Workload: 4.8 x 10 5 Gy/week Workload: 4.8 x 10 5 Gy/week Beam width at the inner wall 8.6 feet in diameter Beam width at the inner wall 8.6 feet in diameter Room size: 55 feet x 30 feet x 25 feet. Room size: 55 feet x 30 feet x 25 feet. All calculations are 0.30 meters from the outer wall. All calculations are 0.30 meters from the outer wall.

21. door D-primaryD-leakage

22. Sample Problem (primary barrier) Sample Problem (primary barrier) Equations: B = Pd 2 /WUT n = log (1/B) Equations: B = Pd 2 /WUT n = log (1/B) S = TVL(1) –(n-1) TVL(2) where n is the number of tenth value layers, S is the total wall thickness and TVL(1) and TVL(2) are the tenth values S = TVL(1) –(n-1) TVL(2) where n is the number of tenth value layers, S is the total wall thickness and TVL(1) and TVL(2) are the tenth values

23. Primary Barrier Primary Barrier Distance = 14.3 meters Leakage = 1 P = 20X10 -6 (Sv/wk) U =1, T = 1/40 (this is a grassy area and rarely occupied) Distance = 14.3 meters Leakage = 1 P = 20X10 -6 (Sv/wk) U =1, T = 1/40 (this is a grassy area and rarely occupied) TVL(1) = 44 cm; TVL(2) = 41 cm Wall thickness is 8.8 feet TVL(1) = 44 cm; TVL(2) = 41 cm Wall thickness is 8.8 feet

24. Secondary Barrier or Ceiling Secondary Barrier or Ceiling B = P d 2 / ((Leakage) WUT) n = log (1/B) S = TVL(1)- (n-1) TVL(2) B = P d 2 / ((Leakage) WUT) n = log (1/B) S = TVL(1)- (n-1) TVL(2)

25. Secondary Barrier Secondary Barrier Distance = 6.38 meters Leakage = 0.001% Distance = 6.38 meters Leakage = 0.001% P = 20X10 -6 (Sv/wk) U =1 T = 1/40 P = 20X10 -6 (Sv/wk) U =1 T = 1/40 TVL(1) = 36 cm; TVL(2) = 33 cm Wall thickness is 2.5 feet TVL(1) = 36 cm; TVL(2) = 33 cm Wall thickness is 2.5 feet

26. DOOR DOOR Reduce the energy and quantity of the neutrons reaching outside of the door. Reduce the energy and quantity of the neutrons reaching outside of the door. Hydrogenous material reduces the neutron dose equivalent to an acceptable level. Hydrogenous material reduces the neutron dose equivalent to an acceptable level. Neutrons are absorbed by (n, gamma) reactions in the door. Neutrons are absorbed by (n, gamma) reactions in the door. The gamma rays (neutron-capture gamma rays are released in the range of a few MeV. The gamma rays (neutron-capture gamma rays are released in the range of a few MeV. Lead in the door is required to attenuate the beam to an acceptable level. Lead in the door is required to attenuate the beam to an acceptable level.

27. DIRECTED SHIELDED DOOR DIRECTED SHIELDED DOOR Typical Sliding Door with the entire door encased in steel. Typical Sliding Door with the entire door encased in steel. l concrete polystyrene lead X-ray beam gap

28. DOOR AT THE END OF THE MAZE INDIRECT DOOR AT THE END OF THE MAZE INDIRECT The neutron contribution as well as the photon contribution is calculated. The neutron contribution as well as the photon contribution is calculated. The main issue is the scattered radiation down the maze. The main issue is the scattered radiation down the maze. The door construction is still the same, lead- poly- lead with the entire door encased in steel. This door is a swinging door and opened and closed pneumatically. The door construction is still the same, lead- poly- lead with the entire door encased in steel. This door is a swinging door and opened and closed pneumatically. EXCELLENT REFERENCE: McGinley, P, Shielding Techniques for Radiation Oncology Facilities,2d ed. EXCELLENT REFERENCE: McGinley, P, Shielding Techniques for Radiation Oncology Facilities,2d ed.

29. SLIDING DOOR SLIDING DOOR

30. AFTER ALL OF THE PLANNING IS COMPLETED

44. ITEMS DURING and POST CONSTRUCTION ITEMS DURING and POST CONSTRUCTION Ensure that the proper shielding report is being used. Ensure that the proper shielding report is being used. Test the concrete for the proper density. Test the concrete for the proper density. Ensure that all radiation protection equipment- warning lights, door interlocks, emergency off buttons-have been ordered and installed. Ensure that all radiation protection equipment- warning lights, door interlocks, emergency off buttons-have been ordered and installed. Ensure that all registrations have been completed. Ensure that all registrations have been completed. Ensure that the final radiation survey was conducted by an authorized expert. Ensure that the final radiation survey was conducted by an authorized expert.

45. HELP HELP HOW DO YOU DEFINE A DEAD PANEL?

46. COMING ATTRACTIONS My panel is dead!!!!!!!!! What does this mean physically? Please send answers to Phil Berry pberry@lanl.gov pberry@lanl.gov This will be for a project: Failure Modes of Digital Detectors Will be to determine the dose for My panel is dead!!!!!!!!

47. Take Home Points Take Home Points Did you identify key personnel needed to build a radiography facility Did you identify key personnel needed to build a radiography facility Did you consider all of the main elements and requirements in the building Did you consider all of the main elements and requirements in the building Be sure you understand the basic elements in performing shielding calculations Be sure you understand the basic elements in performing shielding calculations Follow the project after the planning phase through completion Follow the project after the planning phase through completion

48. THANK YOU FOR YOUR ATTENTION