# Presentation: 779215

## Presentation to ASAC

- R. Casey
- Radiation Shielding: Assumption and Design
- April 24, 2007

## Preliminary Shielding Design Documents for NSLS II

- 1. Linac, NSLS II- TN 12
- 2. Booster & Storage Ring, NSLS II – TN 13
- 3. Storage Ring Supplemental Shielding – TN 21
- 4. Beamlines and Front Ends, NSLS II – TN 14
- 5. Ray Tracing Standards, NSLS II – TN 20
- 6. Activation Analysis, NSLS II – TN 15 & 16

## Radiation Safety Workshop was Recently Conducted

- March 27 – 28, 2007
- Membership
- S. Rokni (Chair) – SLAC
- R. Donahue – ALS
- P. Berkvens – ESRF
- D. Beavis – BNL
- C. Schaefer - BNL

## Rad Safety Workshop	

- Committee reviewed:
- Shielding methodology & assumptions
- Interlocks, Critical Devices, and Area Radiation Monitoring plans.
- Committee concluded:
- 	“Given the status of the project, the design of the bulk shielding of the accelerator complex is well developed and is based on sound principles and reasonable assumptions. “

## Desired Shielding Outcome

- Compliance with DOE Orders, Part 835, and BNL Administrative Controls
- < 25 mRem/year (.25 mSv) on-site to non-NSLS-II personnel; < 5 mrem/year (0.05 mSv) at site boundary
- Radiation exposure to users and staff ALARA – an administrative control level of 100 mRem/year (1 mSv) is desired
- We plan to achieve this through shielding and engineering controls; & supplemental administrative controls
- Based on current experience, we expect annual radiation exposures < < 100 mRem/year (1 mSv) to NSLS staff and users
- After verification, we expect short-term visitors will not be required to have dosimeters routinely

## Shielding Policy

- Accelerator and beam line enclosures will be shielded to reduce exposure at the exterior surface of the shield during typical operation to 0.25 mRem/hr (2.5 uSv) in normally occupied areas to limit the maximum exposure to 500 mrem/year (5 mSv) (assuming 2000 hours occupancy).
- The storage ring outer wall will be shielded to 0.5 mRem/hr (5 uSv/hr) in direct contact with exterior; no full-time occupancy is expected or will be permitted within 1 meter of wall.
- This policy satisfies  DOE Design Goals identified in 10 CFR 835.1002

## Shielding Policy (cont.)

- Shielding calculations will use conservative source terms and attenuation factors
- Abnormal operating conditions, including Maximum Credible Incidents (MCI), will be evaluated
- Additional engineering or administrative controls will be specified based on severity of radiation levels under fault or non-typical conditions.
- Shielding and controls are considered adequate if MCI has low potential for exceeding 100 mRem (1 mSv) and can not exceed 2000 mRem (20 mSv)

## 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
- Beam current 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

## Shielding Policy (cont.)

- Supplemental Administrative control options include:
- Operational procedures for operators and ESH staff during injection and routine operations
- Commissioning and shielding verification procedures
- Shielding configuration control
- Review of accelerator and beam design modifications
- Survey and posting procedures
- Passive area monitors

## Bulk Shielding Calculation Methodology

## Radiation Dose Equivalent Factors at 900(comparison)

| Radiation 
Component | Dose equivalent factors(mrem.m2/J)
(Swanson) | Dose equivalent factors(mrem.m2/J)
(Sullivan) | Dose equivalent factors(mrem.m2/J)
(Shield 11) |
| --- | --- | --- | --- |
| Bremsstrahlung | 2.80 | 1.39 | 1.12 |
| Giant Resonance Neutrons | 0.63 | 0.27 | 0.257 |
| High Energy Neutrons | 0.075 | 0.043 | 0.068 |

## Radiation Attenuation FactorsUsed in Calculations

## Accelerator Operating Conditions used in Calculations

- Linac
- 200 MeV
- 20 nC/pulse
- I hz operation
- Booster
- 3.6 GeV
- 15 nC per pulse
- 1 pulse / minute (typical operation)
- 1 hz operation for 500 hours per year considered
- Storage Ring
- 3.6 GeV
- 500 mA

## Beam Loss Assumptions for Normal Operations

- Linac – 1% distributed loss at 200 MeV
- Linac to Booster injection efficiency – 50%
- Booster losses – 2% loss at any point at 3.6 GeV
- Booster to storage ring injection efficiency – 80%
- Non-injection region – 10% of stored beam losses at any point
- Stops in linac and booster designed for 100% loss at 1 hz

## LINAC Bulk Shielding Estimates

## Booster Bulk Shielding Estimates1

|  | Inboard wall
(cm) | Outboard wall
(cm) | Roof
(cm) |
| --- | --- | --- | --- |
| Booster 
Injection Region2 | 108 | 108 | 98 |
| Booster
Non-injection Region | 95 | 95 | 80 |

**1 ****The Inboard and Outboard walls are at 1 m and the roof at 2 m from the beam**
**2**** Supplemental lead shielding will be required around injection    septum for 1 hz operation**** **
**Booster shielding still in progress as adjacent occupancies are under discussion.**

## Storage Ring Bulk Shielding Estimates

## LINAC - 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 (0.37 mSv/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 Rate = 30 mRem/h (0.3 mSv/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

## 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 = 300 mRem/h (3 mSv/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 = ~ 500 mRem/h (5 mSv/h) **(at the exterior of the ratchet 	wall ~ 0.5 m from the FE) (peak bremsstrahlung shielded with shadow 	shields)
- 100% of stored beam is lost at a point - ~ 8 mRem (0.08 mSv)
_**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

## Bulk Shielding Comparison