1 BROOKHAVEN SCIENCE ASSOCIATES NSLS-II Shielding Workshop R. Casey Activation Issues for NSLS-II March 28, 2007

2 BROOKHAVEN SCIENCE ASSOCIATES Two Analyses have been Conducted for Activation “ Preliminary Activation Analysis of Accelerator Components and Beam stops at NSLS-II ” – NSLS-II Tech Note 15; August 1, 2006 “ Preliminary Activation Analysis of Soil, Air, and Water near NSLS-II Accelerator Enclosures ” - NSLS-II Tech Note 16; August 15, 2006 Will need to be updated to reflect new designs and operating scenarios

3 BROOKHAVEN SCIENCE ASSOCIATES Material Activation Calculations based on power deposited in material Swanson ’ s table for radionuclide production and dose rates utilized

4 BROOKHAVEN SCIENCE ASSOCIATES Beam Stops Beam stops will not routinely receive beam during storage ring operation. Primarily used during commissioning, set-up, and studies. Long-lived radionuclides not likely to have significant build-up Linac stop – could receive 20 nA at 200 MeV (4 watts) Maximum dose rate following a few hours hour of running ~ 2.2 mR/hr at 1 m neglecting self-shielding & activity distribution (Will rapidly decay) Booster stop – could receive 15 nA at 3.5 Gev (52 watts) Maximum dose rate following a few hours of running ~28.7 mR/hr at 1 m neglecting self-shielding (Will rapidly decay) Expected operating times in this mode for both stops < 250 hours/year

5 BROOKHAVEN SCIENCE ASSOCIATES Septum & Scrapers Revised beam loss scenarios now estimate 4.1 nC/min lost on septum (0.24 watts) Septum will be of low significance from activation concern Horizontal scraper will receive 6.2 nC/min (0.36 watt) Scrapers will be of low significance from activation concern

6 BROOKHAVEN SCIENCE ASSOCIATES Summary of Activation in Solids * Not routine operation

7 BROOKHAVEN SCIENCE ASSOCIATES Conclusion for Component Activation Activation will occur in a number of components and must be monitored and controlled. Not expected to be a radiation exposure concern to workers who perform maintenance, but will need to be anticipated and planned

8 BROOKHAVEN SCIENCE ASSOCIATES Ground water High sensitivity at BNL to soil activation and leachate entering ground water Early analysis of issues to determine if engineered systems are needed to protect ground water Included in NEPA Environmental Assessment Considerable discussion with regulators during EA review

9 BROOKHAVEN SCIENCE ASSOCIATES Potential for soil activation evaluated at several high loss points Linac beam stop – can operate at 4 watts ~ 250 hours per year – calculated at 5000 hours per year Booster stop- can operate at 52 watts if receiving beam at 1 hz (estimated at < 250 hours per year) Storage ring septum – loss calculated at 0.62 watts for 5000 hours per year

10 BROOKHAVEN SCIENCE ASSOCIATES Soil Composition and Cross Sections used for Activation Analysis (Cross Sections for 100 MeV Neutrons)

11 BROOKHAVEN SCIENCE ASSOCIATES High Energy Neutron Flux at the Exterior of the Concrete Shield and Average Flux in the Soil

12 BROOKHAVEN SCIENCE ASSOCIATES Tritium and Sodium-22 production rates Conclusion: Soil activation will not be an issue for NSLS-II

13 BROOKHAVEN SCIENCE ASSOCIATES Air Activation Air activation not usually an issue at light sources Evaluated for EA Calculation based on bremsstrahlung interaction in air within accelerator enclosure Production considered for Linac and booster stops and storage ring septum.

14 BROOKHAVEN SCIENCE ASSOCIATES Air Activation Septum is principal source Assumptions 14 nC/min lost at septum 23 m air path uniform mixing within twice air path no air exchange in tunnel 50% of energy in beam available for interaction in air

15 BROOKHAVEN SCIENCE ASSOCIATES Results of Calculation ~10% of occupational DAC Site boundary dose calculated using CAP88 assuming direct release to atmosphere of production rate Site boundary dose < mrem/year Air activation will be insignificant for NSLS-II

16 BROOKHAVEN SCIENCE ASSOCIATES Water Activation Water activation and subsequent discharge to environment is a very sensitive issue at BNL Evaluation for EA necessary Has not been an issue for NSLS – we have never detected tritium in any cooling water system during periodic sampling

17 BROOKHAVEN SCIENCE ASSOCIATES Water activation assumptions We calculate for beam loss on a water cooled device Storage ring septum at 14 nC/min We assume that all bremsstrahlung passes through 2 cm of water We calculate energy deposited in water by bremsstrahlung and the number of radioactive spallation products created. We assume distribution of spallation products as given by Swanson

18 BROOKHAVEN SCIENCE ASSOCIATES Saturation Activities of Radionuclides in the Cooling Water Conclusion Water activation will be inconsequential for NSLS-II Far below discharge limits, e.g. 3 H value at saturation is 5 pCi/l compared to ACL of 1000 pCi/l and drinking water limit of 20,000 pCi/l