1. Operations Section Leader
Radiological Hazard Analysis for Normal Conducting Linac Beam commissioning
Lali Tchelidze
Operations Section Leader
Accelerator Division
ESHAC meeting
April 11, 2018

2. Outline
Introduction
Radiological hazard analysis – prompt and residual radiation
Radiological hazard analysis – activated air
Radiological hazard analysis – earthquake
Radiological hazard analysis – fire in the tunnel
Radiological hazard analysis – lightning
List of required RSF (radiation safety functions) for NC linac beam commissioning
Defense in Depth analysis
(ESS operational limits and conditions)

3. Before I start
By the ESS management decision, the AD safety group is now gone
All work/support coming from this group is now supposed to come from ESH
No resources are foreseen in AD to provide support in conventional safety matters, nor for licensing application (currently I remain as AD representative in licensing team)

4. Introduction
This presentation covers radiological hazard analysis for the normal conducting linac beam commissioning only.
Beam commissioning is planned simultaneously with the installation activities in the downstream part of the linac tunnel.
Beam commissioning is planned in the following steps:
Ion source and LEBT beam commissioning (75 KeV, not covered in this presentation)
RFQ and MEBT beam commissioning (3.6 MeV)
DTL1 beam commissioning (22 MeV)
DTL2 to DTL4 beam commissioning (up to 75 MeV)

5. Introduction

6. Radiological hazard analysis – prompt and residual radiation – list of events
List of analysed events:
EA-13 Planned beam commissioning
EA-14 Off-normal beam loss
EA-15 Maintenance work in accelerator tunnel
EA-16 FC shielding missing

7. Radiological hazard analysis – prompt and residual radiation – dose rate plots
EA-13 Planned beam commissioning
Maximal dose rates for 1 W/m beam loss
ESS K. Batkov

8. Radiological hazard analysis – prompt and residual radiation – dose rate plots

9. Radiological hazard analysis – prompt and residual radiation – beam limitations
Energy
FC Location
Average current
Average power (W)
Beam modes
(to be discussed further) 22
DTL4 ws
8.8 µA
194
Probe, Fast, Slow, Fat probe 40
3.0 µA
132
Probe, Slow, Fat probe, Fast(10Hz) 57
1.4 µA 80
Probe, Fat probe, Slow(0.3Hz), Fast (3Hz) 74
1.2 µA 89
DTL2 w/o s
8.8 nA
0.19
Probe(0.2Hz)
3.0 nA
0.13
Probe(0.1Hz)

10. Radiological hazard analysis – prompt and residual radiation – list of RSF
Safety function
SSCI2S
Event class
Functional Group
RSF-3 attenuate radiation emitted from proton beam line
Structural part of the tunnel and earth berm; all other permanent and movable shielding H1
Operational
RSF-138 Ensure to stop the proton beam on FC at predefined destinations
Faraday cup (in MEBT, end of DTL2 and end of DTL4) BPCS & MPS-ID
RSF-139 attenuate radiation from beam on FC interaction
FC shielding and TSW
RSF-140 monitor and limit average beam current to values in “Table 3”
BPCS
RSF-32 Detect elevated prompt dose rates outside accelerator (normal conducting linac) shielding and alert/shut the beam off
Dose rate shall be averaged over any one-hour period outside of TSW
REMS & PSS1

11. Radiological hazard analysis – prompt and residual radiation – shielding
Permanent shielding structure:
Concrete structure (with penetrations)
“Movable” shielding structure:
FEB chicane wall (ESS )
Shielding in FEB side wall penetrations – not modeled (ESS )
Drop hatch shielding - not modeled (ESS )
Stubs shielding – not modeled yet (ESS )
Alignment penetration shielding – not modeled (ESS )
Temporary shielding walls (ESS )

12. Radiological hazard analysis – prompt and residual radiation – shielding
Opening for alignment penetration
Concrete tunnel
Drop hatch
Stubs shielding
Stubs
FEB
FEB side wall penetrations
FEB chicane
(wall)
HVAC inlet ducts

13. Radiological hazard analysis – prompt and residual radiation
EA-14 Off-normal beam loss
Safety function
SSCI2S
Event class
Functional Group
RSF-32 Detect elevated prompt dose rates outside accelerator (normal conducting linac) shielding and alert/shut the beam off
REMS & PSS1 H2
Operational

14. Radiological hazard analysis – prompt and residual radiation
EA-15 Maintenance work in accelerator tunnel
Residual Radiation (100 days irradiation, 4 hours cooling)
Safety function
SSCI2S
Event class
Functional Group
AM-10 Limit exposure by applying ALARA approach NA H1
Operational

15. Radiological hazard analysis – prompt and residual radiation
EA-16 FC shielding missing
Safety function
SSCI2S
Event class
Functional Group
RSF-32 Detect elevated prompt dose rates outside accelerator (normal conducting linac) shielding and alert/shut the beam off
REMS & PSS1 H2
Operational

16. Radiological hazard analysis – activated air
Highest expected DAC (derived air concentration) value for planned beam commissioning beam losses is 3.45x10-4 DAC, or 6.9 µSv in 2000 hours.
Highest expected DAC values for the 74 MeV beam on Faraday cup is approximately 1.86x10-3 DAC, or 37.2 µSv in 2000 hours.
No radiation safety functions are required.
ESS , A. Polato

17. Earthquake On-going discussions.
No agreement, yet, about the worst case scenario.

18. Fire in the tunnel On-going. Open issues: Worst case scenario
Whether or not to credit fire dumpers in safety analysis.

19. Lightning
Planned, but not started.

20. List of RSF for NC linac beam commissioning
Safety function
SSCI2S
Event class
Functional Group
RSF-3 Attenuate radiation emitted from proton beam line
Structural part of the tunnel and earth berm; All other permanent and movable shielding H1
Operational
RSF-138 Ensure to stop the proton beam on FC at predefined destinations
Faraday cup (in MEBT, end of DTL2 and end of DTL4) BPSC & MPS-ID
RSF-139 attenuate radiation from beam on FC interaction
FC shielding and TSW
RSF-140 monitor and limit average beam current to values in Table 3
BPCS
RSF-32 Detect elevated prompt dose rates outside accelerator (normal conducting linac) shielding and alert/shut the beam off
(Dose rate shall be calculated over any one-hour period outside of TSW for H1)
REMS & PSS1
H1, H2
AM-10 Limit exposure by applying ALARA approach NA

21. Thank you!