Comparative Analysis of Neutron Sources Produced by Low-Energy Electrons and Deuterons for Driving Subcritical Assemblies

D. Naberezhnev, Y. Gohar, H. Belch, J. DuoArgonne National Laboratory, Department of Energy, USA

Igor BolshinskyIdaho National Laboratory, Department of Energy, USA

Fifth International Workshop on the Utilization and Reliabilityof High Power Proton Accelerators

Mol, BelgiumMay 6-9, 2007

Comparative Analysis of Neutron Sources Produced by Low-Energy Electrons and Deuterons for Driving Subcritical Assemblies

Introduction

A conceptual design of an accelerator driven subcritical assembly has been developed using the existing accelerators at Kharkov Institute of Physics and Technology (KIPT) in Ukraine.

Two different external neutron source options were examined for driving the subcritical assembly. Electrons with energies below 200 MeV and deuterons with energies below 100 MeV were considered.

Comparative analysis of these two options is presented and discussed.

Ukraine Accelerator Driven Subcritical Assembly Facility Mission

Produce medical isotopes and provide neutron source for performing neutron therapy procedures.

Provide capabilities for carrying basic and applied research utilizing the radial neutron beam ports around the subcritical assembly.

Support the Ukraine nuclear power industry by providing the capabilities to perform reactor physics experiments and to train young specialists.

Facility Conceptual Design Overview

Vertical Cross Section Through the Facility

View Inside the Subcritical Assembly Showing Overall Arrangement

Comparative Analysis of Neutron Sources Produced by Low-Energy Electrons and Deuterons for Driving Subcritical Assemblies

Study Objective:

Maximize the neutron production from the available beam power and define the optimal beam parameters.

Study Parameters:Neutron source strength

Neutron spatial and energy distributions

Energy deposition in the target material

Beam radius relative to the target radius

Target geometrical configurations

Thermal hydraulics results

Thermal stress results

Target Fabrication

Neutron Yields from Electron Interactions

0.00

0.05

0.10

0.15

50 100 150 200

W

U

Neu

trons

per

ele

ctro

n

Electron energy, MeV

1.0 1014

2.0 1014

3.0 1014

4.0 1014

5.0 1014

50 100 150 200

WU

Neu

trons

per

sec

ond

Electron energy, MeV

Neutron yield per electron from uranium and tungsten targets as a function of the

electron energy

Neutron source strength from tungsten and uranium targets as a function of the electron energy for 100 kW beam power

Neutron Spectrum from Electron Interactions

Neutron spectrum from tungsten target material for different electron beam energies

Neutron spectrum from uranium target material for different electron beam energies

0

0.04

0.08

0.12

0.16

0.2

0.24

0.01 0.1 1 10 100

100 MeV200 MeV

Neu

tron

Frac

tion

Energy, MeV

0

0.05

0.1

0.15

0.2

0.25

0.01 0.1 1 10 100

100 MeV200 MeV

Neu

tron

Frac

tion

Energy, MeV

Neutron Yields from Deuteron Interactions

Neutron yields from deuteron interactions with beryllium as a function of the deuteron energy

Neutron source intensity from deuteron interactions with beryllium as a function of the deuteron beam energy normalized for 100 KW beam power

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0 20 40 60 80 100 120

Neu

trons

per

deu

tero

n

Deuteron energy, MeV

0

5 1014

1 1015

1.5 1015

2 1015

2.5 1015

0 20 40 60 80 100 120

Neu

tron

inte

nsity

, n/s

Deuteron energy, MeV

Neutron Spectra Generated from Deuteron-Beryllium Interactions for Different Deuteron Energies

0

0.05

0.1

0.15

0.2

0.01 0.1 1 10 100

20 MeV50 MeV100 MeV

Neu

tron

fract

ion

Neutron energy, MeV

Spatial Energy Deposition in the Tungsten Target Material

Spatial energy deposition per electron in the tungsten target material for different electron energies

Spatial energy deposition in the tungsten target material normalized to 2 KW/cm2

on the beam window for different electron energies

0

20

40

60

80

100

120

0 2 4 6 8 10

50 MeV100 MeV150 MeV200 MeV

MeV

/cm

3 per

ele

ctro

n

Target Length, cm

0

500

1000

1500

2000

0 2 4 6 8 10

50 MeV100 MeV150 MeV200 MeV

Hea

ting

rate

, W/c

m3

Target length, cm

Spatial Energy Deposition in the Uranium Target Material

0

20

40

60

80

100

120

0 2 4 6 8 10

50 MeV100 MeV150 MeV200 MeV

MeV

/cm

3 per

ele

ctro

n

Target length, cm

0

625

1250

1875

2500

0 2 4 6 8 10

50 MeV100 MeV150 MeV200 MeV

Hea

ting

rate

, W/c

m3

Target length, cm

Spatial energy deposition per electron in uranium target material for different electron energies

Spatial energy deposition in uranium target material normalized to 2 KW/cm2

on the beam window for different electron energies

Neutron Yields as a Function of the Target Length

Number of neutrons per electron from pure tungsten material as a function of the target length for the 200 MeV electron energy

0.0698

0.0699

0.0700

0.0701

0.0702

0.0703

0.0704

0.0705

0.0706

5 6 7 8 9 10

Neu

tron

per e

lect

ron

Target Length, cm

0.1390

0.1395

0.1400

0.1405

0.1410

0.1415

0.1420

0.1425

0.1430

5 6 7 8 9 10

Neu

tron

per e

lect

ron

Target Length, cm

Number of neutrons per electron from pure uranium material as a function of the target length for the 200 MeV electron energy

Spatial Energy Deposition in the Beryllium Target Material

Spatial energy deposition per deuteron in pure beryllium target material for different deuteron energies

0

50

100

150

200

250

300

0 0.5 1 1.5 2 2.5 3 3.5

20 MeV50 MeV100 MeV

MeV

/cm

3 per

deu

tero

n

Target length, cm

0

5000

1 104

1.5 104

2 104

2.5 104

3 104

0 0.5 1 1.5 2 2.5 3 3.5

20 MeV50 MeV100 MeV

heat

ing

rate

, W/c

m3

Target length, cm

Spatial energy deposition in pure beryllium target material for different deuteron energies normalized to 2 KW/cm2 on the beam window

Neutron Yields as a Function of the Target Length

Neutron yield as a function of pure beryllium target length from 23 MeV deuteron

0.004

0.006

0.008

0.01

0.012

0.014

0.016

0.018

0 2 4 6 8 10 12

Neu

trons

per

deu

tero

n

Target length, cm

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0 2 4 6 8 10 12

Neu

trons

per

deu

tero

nTarget length, cm

Neutron yield as a function of pure beryllium target length from 100 MeV deuteron

Comparison of different options for producing neutron source

Exploded Assembly View of the Updated Uranium Target Design

Spatial Energy Deposition Distributionin the Uranium Target Disks

W/cm3

Temperature Distribution in the UraniumTarget Disks

Temperature,°C

Third Disk Midplane Temperature Distribution(The Highest Disk Temperature)

Temperature,°C

Third Disk Thermal Stress(The Disk with Highest Thermal Stress)

Conclusions

The Comparative analysis of neutron sources produced by low-energy electrons and deuterons show that:

An electron accelerator with electron energy in the range of 150 to 200 MeV is preferred for producing neutron source.

The uranium target material produces the highest neutron yield per electron.

The uranium target with 100 KW electron beam produces 3.3x1014 n/s.

The thermal hydraulics analyses of the uranium target operating with the 100 KW electron beam power satisfy the engineering design requirements.

The peak thermal stresses (secondary stress) is less than the yield strength of the uranium target material.