Design of local shielding for the IFMIF/EVEDA beam dump

M. García1,2, F.Ogando1,2, P. Ortego3, J.M. Arroyo4, B.Brañas4, C. Töre3, D. López1,2, P. Sauvan1,2, A. Mayoral1, J. Sanz1,2

1) UNED, C/ Juan del Rosal 12, 28040 Madrid, Spain2) Instituto de Fusión Nuclear, C/ José Gutiérrez Abascal 2, 28006 Madrid, Spain3) SEA, Madrid, Spain4) CIEMAT, Avda Complutense, Madrid, Spain

1. Introduction and Scope of the problem

2. Methodology

3. Design and optimization of the IFMIF/EVEDA Beam Dump shielding

4. Results

5. Conclusions

1. Introduction and Scope of the problem

2. Methodology

3. Design and optimization of the IFMIF/EVEDA Beam Dump shielding

4. Results

5. Conclusions

INTRODUCTION AND SCOPE OF THE PROBLEM: FRAMEWORK

Work within the frame of the:

Spanish participation in IFMIF/EVEDA Accelerator System Group

•Design and construction of a Beam Dump for the EVEDA accelerator prototype

•Radioprotection and Safety

two European home-teams involved for the EVEDA phase: CEA (France) and UNED/CIEMAT (Spain).

INTRODUCTION AND SCOPE OF THE PROBLEM: FRAMEWORK

Work within the frame of the:

Spanish participation in IFMIF/EVEDA Accelerator System Group

•Design and construction of a Beam Dump for the EVEDA accelerator prototype

•Radioprotection and Safety

two European home-teams involved for the EVEDA phase: CEA (France) and UNED/CIEMAT (Spain).

INTRODUCTION AND SCOPE OF THE PROBLEM: IFMIF/EVEDA

INTRODUCTION AND SCOPE OF THE PROBLEM: IFMIF/EVEDA

Each deuteron accelerator: 125 mA up to 40 MeV 1017 neutrons/s 14 MeV

INTRODUCTION AND SCOPE OF THE PROBLEM: IFMIF/EVEDA

IFMIF/EVEDA

•Deuterons up to 9 MeV•125 mA•Beam Dump

EVEDA Phase: Engineering Validation and Design.

In construction phase at Rokkasho

(Japan)

INTRODUCTION AND SCOPE OF THE PROBLEM: IFMIF/EVEDA

For the present design of both building and copper Beam Stop, we explore if a local BD shielding could be defined in compliance with two radioprotection requirements:

1.- Are the dose rates outside the accelerator vault during accelerator operation below the required levels for workers and public? (workers 12.5 Sv/h, public 0.5 Sv/h)

2.- Is man-access for maintenance inside the accelerator vault feasible during beam- off phases?

Copper cone: to stop deuteron beam

North: Limit 12.5 Sv/h

South: Limit 12.5 Sv/h

East: Limit 0.5 Sv/h

West: 0.5 Sv/h

Concrete thickness fixed 1.5m

INTRODUCTION AND SCOPE OF THE PROBLEM: IFMIF/EVEDA

Inner cone of 5mm thickness, 300mm base diameter and 2500 mm length.Water channel (refrigeration) of 7mm thicknessOuter cone of 3mm thicknessWater (refrigeration) between the outer cone and the cartridgeCylindrical cartridge made of steel of 9mm thickness. Outer diameter of the cartridge: 508mm

Beam Dump geometry:

Neutron source to shield: 4.6484 1014 n/s

INTRODUCTION AND SCOPE OF THE PROBLEM: IFMIF/EVEDA

Deuteron deposition in the copper cone

1. Introduction and Scope of the problem

2. Methodology

3. Design and optimization of the IFMIF/EVEDA Beam Dump shielding

4. Results

5. Conclusions

ACAB

Neutron and deuteron fluxes

MCNPX

Isotopic inventory & Gamma Source

Gamma Dose

TraceWin

Module for Deuteron source modeling

BE

AM

O

FF

Neutron and gamma Fluxes

Neutron and gammaDoses

Dose conversion factors

(ICRP74) BE

AM

O

NMETHODOLOGY: GENERAL OUTLINE

Module for neutron Source modeling

Dose conversion factors

(ICRP74)

METHODOLOGY: GENERAL OUTLINE

Obtaining the neutron source increases significantly the efficiency of the Monte Carlo simulation since in deuteron-Cu interaction around 10000 deuterons are needed to produce one neutron

How to model the neutron source due to the deuteron interaction with the copper cone?

The starting point is the deuteron particle position and energy at the copper cone entrance provided by the TraceWin code.

First step: to determine the equivalent deuteron source point taking into account the energy and particle deposition of the deuteron beam in the copper cone from TraceWin

Second step: to obtain the neutron source arising from the deuteron-copper interaction

1. Introduction and Scope of the problem

2. Methodology

3. Design and optimization of the IFMIF/EVEDA Beam Dump shielding

4. Results

5. Conclusions

DESIGN AND OPTIMIZATION OF THE IFMIF/EVEDA BEAM DUMP SHIELDING

Water-based preliminary design: Starting point1 meter water shielding lateral and rear

DESIGN AND OPTIMIZATION OF THE IFMIF/EVEDA BEAM DUMP SHIELDING

Water-based preliminary design: Starting point1 meter water shielding lateral and rearLateral gamma doses by (n,g) reactions cause doses higher than the limitDose by neutrons in the north produces dose rates higher than the limitAn optimization of the shielding is needed

AMBIENT DOSE EQUIVALENT RATE BY NEUTRONS (Sv/h)

AMBIENT DOSE EQUIVALENT RATE BY PHOTONS (Sv/h)

DESIGN AND OPTIMIZATION OF THE IFMIF/EVEDA BEAM DUMP SHIELDING

Optimized design (lateral area):Considering better lateral shield which works on both neutron and gamma rays, there is a need for at least two layers of different materials:Internal shield to absorb and/or moderating the energetic neutron flux from beam stop.External shield to attenuate the gamma rays originated in the internal shield from (n,g).Front-lateral shield (removable)

Optimized configuration: 50 cm water + 25 cm iron30 cm polyethylene + 25 cm iron

DESIGN AND OPTIMIZATION OF THE IFMIF/EVEDA BEAM DUMP SHIELDING

Optimized design (front area):Diagnostics room: Designed to:

1. Confine the highest residual dose rates allowing manual maintenance in the accelerator area

2. Reducing prompt dose rates in the north wall by collimating the neutron current escaping the beam dump during operation

Lead shutter: Designed to reduce residual dose rates in the accelerator area

Lead shutterDiagnostics room

Accelerator areaBD cell

DESIGN AND OPTIMIZATION OF THE IFMIF/EVEDA BEAM DUMP SHIELDING

dipole

quadrupoles

Diagnosticsroom

water

iron

polyethylene

North

South

East West

Beam Dump cell area: Lateral and rear shielding: water (50 cm) + iron (25 cm). Fixed solution.Front-lateral shielding: polyethylene (30 cm) + iron (25 cm). Removable solution.Accelerator area:Diagnostics room: to confine higher beam-off dose rates and allow manual maintenance in the accelerator area on beam-off phase.

Accelerator Area

Beam Dump cell Area

This is a conceptual design

1. Introduction and Scope of the problem

2. Methodology

3. Design and optimization of the IFMIF/EVEDA Beam Dump shielding

4. Results

5. Conclusions

RESULTS: MAXIMUM PROMPT DOSE RATES AT THE EXTERNAL SURFACES

dipole

quadrupoles

Diagnosticsroom

water

iron

polyethyleneAccelerator Area

Beam Dump cell Area

Maximum prompt dose rates (external surfaces)

North South East West

Dose (µSv/h) 2 2.2 0.26 0.29

Limit (µSv/h) 12.5 12.5 0.5 0.5

Dose by pothons (%)

50 83 84 59

Effect of diagnostics room on dose rate by neutrons

Without room With room Ambient dose equivalent rate

Ambient dose equivalent rate

RESULTS: RESIDUAL DOSE RATES INSIDE THE ACCELERATOR VAULT

Beam-off configuration:

Residual dose rates(irradiation 6 months continuous full power, 1 day cooling time)

Manual maintenance is possible in the Beam Dump cell andIn the accelerator area without restrictions (dose rates lower than 12.5 µSv/h).

Detector Dose Rate due to deuteron activation of the copper cone (µSv/h)

Dose rate due to neutron activation of the 25 cm iron layer (iron plus Co 2500 ppm) (µSv/h)

Total Dose rate

(µSv/h)1 4.6 0.5 5.12 2.1 2.5 4.63 0.1 0.1 0.24 533 - 5335 251 - 2516 3.6 - 3.67 12 - 128 1.5 - 1.5

Ambient dose equivalent rate

Lead plug thickness: 9 cmLead sheet thickness: 1 cm

1. Introduction and Scope of the problem

2. Methodology

3. Design and optimization of the IFMIF/EVEDA Beam Dump shielding

4. Results

5. Conclusions

CONCLUSIONS

A beam dump shield for the IFMIF/EVEDA facility has been designed.

This model makes use of an optimized combination of materials for neutron and photon shielding and has been achieved after successive optimization steps.

The main goals achieved of the design are:1. Maximum beam-on dose rates outside the accelerator vault fulfill the limits (both in the close workers areas and outside the facility for public).

2. Maximum beam-off dose rates allow hands-on maintenance in most of the accelerator vault, reducing the high dose rate area to a small dedicated room.

Future work must be focused on i) diagnostics room optimization and ii) specific solutions for the construction phase.

Thank You for your attention