1 BROOKHAVEN SCIENCE ASSOCIATES Summary of Shielding Calculations for NSLS2 Accelerators P.K. Job Radiation Physicist Peer Review 2007 March 2 BROOKHAVEN SCIENCE ASSOCIATES Outline Bulk Shielding Policy Calculational Tools and Procedures Beam Loss Assumptions Linac Shielding Design Storage Ring and Booster Shielding Electron Beam Stops Supplemental Shielding in the Storage Ring 3 BROOKHAVEN SCIENCE ASSOCIATES Desired Shielding Outcome Compliance with DOE Orders, Part 835, and BNL Administrative Controls < 25 mRem/year on-site to non-NSLS-II personnel; < 5 mrem/year at site boundary Radiation exposure to users and staff ALARA an administrative control level of 100 mRem/year is desired We plan to achieve this through shielding and engineering & supplemental administrative controls Based on current experience, we expect annual radiation exposures < < 100 mRem/year to NSLS staff and users 4 BROOKHAVEN SCIENCE ASSOCIATES Shielding Policy Accelerator enclosures & hutches shielded to 0.25 mrem/hr, 500 mRem/year based on 2000 hours of exposure per year at the exterior of the shield (< 0.5 mrem/h on contact) Hutches are being considered further for 0.05 mRem/hr They potentially represent a more significant source of exposure Personnel more likely to be in vicinity of hutches 5 BROOKHAVEN SCIENCE ASSOCIATES Shielding Policy (cont.) Calculations use conservative shielding criteria and source terms Abnormal operating conditions, including Maximum Credible Incidents (MCI), are evaluated Additional engineering or administrative controls are specified based on severity of radiation levels under fault conditions. Shielding and controls are considered adequate if MCI has low potential for exceeding 100 mRem and can not exceed 2000 mRem 6 BROOKHAVEN SCIENCE ASSOCIATES Shielding Policy (cont.) Engineering control options include: Additional shielding (e.g. shadow shields, localized shields) Beam loss monitors with alarm in control room and (perhaps) interlock function Area radiation monitors at the occupied areas with alarm locally and in control room and interlock function 7 BROOKHAVEN SCIENCE ASSOCIATES Shielding Policy (cont.) Supplemental Administrative control options include: Operational procedures for operators and ESH staff during injection and routine operations Survey and posting procedures Commissioning and shielding verification procedures Shielding configuration control Review of accelerator and beam design modifications Passive area monitors 8 BROOKHAVEN SCIENCE ASSOCIATES Radiation Sources Considered for calculations Bremsstrahlung (High Energy Photons) Bremsstrahlung produced Neutrons Synchrotron Radiation (Low Energy x-rays) 9 BROOKHAVEN SCIENCE ASSOCIATES Calculational Tools and Procedures Semi-empirical Methods (Swanson, Shield11) Analytical Methods (PHOTON, STAC8) Monte Carlo Methods (EGS4) 10 BROOKHAVEN SCIENCE ASSOCIATES LINAC Shielding LINAC Parameters used in Shielding Calculations Beam energy200 MeV Beam current20 nA Bunch Pattern500 pC/ 40 bunches Frequency1 Hz Tunnel Length60 meters Tunnel width x height4 x 3 m 2 Position of beam from floor1 m Power4 watts 11 BROOKHAVEN SCIENCE ASSOCIATES LINAC Shielding (Beamloss Assumptions) 12 BROOKHAVEN SCIENCE ASSOCIATES LINAC Bulk Shielding Estimates 13 BROOKHAVEN SCIENCE ASSOCIATES LINAC - Maximum Credible Radiation Incidents 100 % of maximum accelerated beam is lost at some location in the linac enclosure, (20 nC/s is continuously lost) Dose Rate = 37.5 mrem/h (at the exterior of shield on contact) 100 % injected beam to the booster is continuously lost at the linac- booster injection septum at 1 Hz. Dose rates at the exterior of the floor wall will be; Dose Rate = 15 mrem/h Mitigation/ control to prevent significant exposure Area Radiation Monitors with beam shut off capability Beam current monitors in the LINAC Additional supplementary shielding at the septum/stop (lead/poly) Operating procedures for operators during injection 14 BROOKHAVEN SCIENCE ASSOCIATES Booster Parameters used in Shielding Calculations Beam Energy 3.5 GeV Repetition Rate 1 Hz Accelerated Charge15 nC No of Electrons per Fill9.36 Total Energy in the Booster52.5 Joules Interval Between Booster injections 72 sec (Normal operating mode) 15 BROOKHAVEN SCIENCE ASSOCIATES Storage Ring Parameters used in Shielding Calculations Beam energy3.5 GeV Beam current500 mA Beam Life Time2 hours Tunnel Circumference780 meters Stored Charge1.3 C Stored Electrons8.1 Stored Energy4540 Joules Interval between booster injections 72 Seconds (14 nC is lost in the Storage Ring in every minute) 16 BROOKHAVEN SCIENCE ASSOCIATES Storage Ring - Beamloss Assumptions (Beamloss Scenario 1) 17 BROOKHAVEN SCIENCE ASSOCIATES Storage Ring - Beamloss Assumptions (Beamloss Scenario 2) 18 BROOKHAVEN SCIENCE ASSOCIATES Storage Ring Beamloss (Summary) 19 BROOKHAVEN SCIENCE ASSOCIATES Beamloss Assumptions for Booster and Storage ring 20 BROOKHAVEN SCIENCE ASSOCIATES Booster Bulk Shielding Estimates Inboard wall (cm) Outboard wall (cm) Roof (cm) Booster Non-injection region 95 cm 80 cm The Inboard and Outboard walls are at 1 m and the roof at 2 m from the beam 21 BROOKHAVEN SCIENCE ASSOCIATES Storage Ring (Bulk Shielding Estimates ) 22 BROOKHAVEN SCIENCE ASSOCIATES Storage Ring (Bulk Shielding Estimates) 23 BROOKHAVEN SCIENCE ASSOCIATES Storage Ring (Credible Radiation Incidents) 100 % injected beam from the booster to storage ring is lost at any location in the storage ring (15 nC/s is continuously lost at some location other than injection region) Dose Rate = 277 mrem/h (at the exterior of the experimental floor wall on contact) 100 % injected beam from the booster to storage ring is lost at any beamline front end due the shorting of a bending magnet (15 nC/s is continuously lost at a front end component) Dose Rate = 412 mrem/h (at the exterior of the ratchet wall ~ 0.5 m from the FE) (peak bremsstrahlung shielded with shadow shields) Mitigation/controls to prevent significant exposure Area Radiation Monitors with beam shut off capability Beam loss monitors inside the Storage Ring Additional Supplementary Shielding (Shadow Shields) Operating procedures for operators defining actions during injection 24 BROOKHAVEN SCIENCE ASSOCIATES Bulk Shielding Comparison Bulk Shield at Experimental Floor Side cm 25 BROOKHAVEN SCIENCE ASSOCIATES Bulk Shielding Comparison cm 26 BROOKHAVEN SCIENCE ASSOCIATES Beam Stop Dimensions Fe Beam Stop Dimensions for the 3.5 GeV e - Beam (to Contain 99 % of the EM Shower) 35 cm (20 X 0 ) 4.2 cm (3 M) e - Beam Fe Cylinder 27 BROOKHAVEN SCIENCE ASSOCIATES LINAC Beam Stop (Supplemental Shielding) 28 BROOKHAVEN SCIENCE ASSOCIATES Booster Beam Stop (Supplemental Shielding) 29 BROOKHAVEN SCIENCE ASSOCIATES Shadow Shields (Shield for Forward Peaked Bremsstrahlung) 30 BROOKHAVEN SCIENCE ASSOCIATES Shadow Shield Thickness 15 cm Pb 31 BROOKHAVEN SCIENCE ASSOCIATES Radiation Shielding Design for NSLS II Shielding Design Documents 1. Linac, NSLS II- TN Booster & Storage Ring, NSLS II TN Storage Ring Supplemental Shielding TN Beamlines and Front Ends, NSLS II TN Ray Tracing Standards, NSLS II TN Activation Analysis, NSLS II TN 15 & 16