The 11th Symposium on Accelerator Science and Technology, Harima Science Garden City, 1997

. Neutron Factory Project at KURRI
Yoichi KAWASE, Makoto INOUE* and·Future Plan Working Group
Research Reactor Institute, Kyoto University, Kumatori, Sennan, Osaka, 590-04 JAPAN*Institute for Chemical Research, Kyoto University, Uji, Kyoto, 611 JAPAN

Abstract
An intense neutron source based on a hybrid
system of linear accelerators and a subcriticalassembly has been proposed as a future plan of
the Research Reactor Institute, Kyoto University(KURRI). The injector linac provides 300 MeV,0.3mA protons to produce neutrons which aremultiplied by a subcritical uranium assembly. Thissystem is expected to bring new opportunities as asecond generation neutron source at KURRI.

1. Introduction
The Kyoto University reactor(KUR) has been
providing low energy steady neutrons for various
research fields such as reactor physics, nuclearphysics, nuclear chemistry, biology and medicine.
According to the recent progress in each field,
strong requirements for high energy and pulsed
neutrons have increased and a "new neutron
source" has been discussed in the working groupof the future plan committee of KURRI to meetthe requirements. A particle accelerator andneutron multiplier combination is proposed as oneof possible candidates.
The particle accelerator part of the Neutron
Factory project is given in this report and thetarget part has been elsewhere [1].

Many requirements for various kinds ofneutrons arise from research experiences at KUR.
Pulsedneutrons
for· neutron
scatteringexperiments are strongly required by solid s~te
physicists. Ultra cold neutrons, on the other hand,are very important for elementary particle physics.
The medical use of epithermal neutrons by theBoron Neutron Capture Therapy(BNCT) method
is hopeful on the base of experiences at KUR.
We propose here the Neutron Factory, a hybrid
system of particle accelerators and a subcriticalassembly, which is shown in Fig. 1. Deuterons orhydrogen molecules of 100 rnA beam intensity
extracted from a high current ion source areaccelerated to 400 keV by the first RFQ . The
second RFQ makes the beam energy high up to 2
MeV by the 10% duty pulse operation. The drifttube-line (DTL) linear accelerator is operated at
1% duty to get the beam energy of 20 MeV . For
the higher energy than 20 MeV, the proton
acceleration is economical. Therefore the 20 MeV
Hz+ beam which can be accelerated by thedeuteron linac is stripped before the second stage
DTL. Finally, we obtain a proton beam of 300
MeV and 0.3 rnA by a Disk and Washer (DAW)
linear accelerator.
In each stage of the particle energy, every
variety of neutrons become available as follows.
1) 14 MeV neutrons

2. Particle accelerators

The primary particles to produce neutrons
efficiently are high energy proton and deuteron
which can be accelerated advantageously by alinear accelerator(UNAC) at high beam intensity[2]. In order to obtain intense neutrons, theattainable energy of the primary particle should beas high as possible. However, taking into accountthe present situation at KURRI, it is desirable thatthe reactor technology is effectively applied to
produce neutrons in combination with a moderate
size linac.

Among the neutron producing reactions, the(D, T) reaction has the largest cross section. It
reaches 5 bam at 105 keV deuteron bombarding
energy. By using 400 keV deuterons from the firstRFQ, intense 14 MeV neutrons can be generated
and used for the study of fusion reactor materials.
Difficult problems arising from a large amount oftritium targets should be solved.
2) Epithermal neutrons

The second RFQ generates about 3 MeV
neutrons by the deuteron bombardment on the Betarget.

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Thellth Symposium on Accelerator Science and Technology, Harima Science Garden City, 1997

NEUTRON FACTORY PROJECT at KURRI

11-oo<E--------First Stage (3 years) -----*oE----- Second Stage

2 MeV

20 MeV--------:>~~300 MeV

Pulsed • Steady Neutron
14 MeV
NeutronEpithermal
NeutronFast & Thermal
Pulsed Neutron

Fast & Thermal
Pulsed Neutron

1 x1 0 14 n/s (peak)

1x1 0 16n/s (peak)

2x1 0 13n/s

1x1 0 13n/s (mean)

1x1 0 14 n/s (mean)

1.9 x1 0 l7 n/s (peak) 1.2 x1 0 lBn/s (peak)
5.6 x1 0 14n/s (mean) 3.7 x1 0 lSn/s (mean)

Fusion Reactor
Material

Medical Use

Reactor Physics

IS : ion Source
RFQ : RFQ Deuteron Linear Accelerator
DTL : Drift Tube Line Proton Linear Accelerator
DAW : Disk And Washer Proton Linear Accelerator
T: Tritium Target
Be/U : Beryllium I Uranium Target

High Energy
Neutron Physics

Fast & Thermal
Pulsed Neutron

Neutron
Scattering

Controlled Irradiation
Activation Analysis
Cold Neutron Physics
Rl Production

Fig.1 Block diagram of Neutron Factory

They can be moderated down to epithermal
neutrons which are efficiently used for the BNCT. The fundamental study on BNCT presently donewith thermal neutrons at KUR can be upgraded byutilizing high quality epithermal neutrons.
3) High energy pulsed neutrons

The 20 MeV deuterons obtained by the DTLLINAC can produce about 10 MeV pulsed
neutrons by the 9Be(d,n) stripping reaction. The
DTL is operated at 1% duty and high energy
neutron experiments such as the T. 0. F.
spectroscopy in reactor physics become possible.
4) Intense pulsed neutrons

The final energy and beam intensity of the
primary particles are planned to be 300 MeV and
0.3 rnA, respectively, which allow the mass
production of high energy neutrons by a spallation
reaction. We can expect the neutron intensity of
1. 2xl018 n/s at peak and 3. 7x1015 n/s in mean,

which enables neutron scattering experiments forstructure analysis of condensed matters .
5) Neutrons for irradiations

A final goal of the Neutron Factory project is toinject spallation neutrons into a subcriticalassembly to multiply them safely and efficiently.
Details of the target system should be studied[ 1].
Intense neutrons can make great evolution in
research fields such as precisely controlled
irradiation of materials and the cold neutron
physics which require much more than presently
available at KUR.
In Fig. 2, the layout of the Neutron Factory is
illustrated including KUR and KUCA. The low
energy deuteron beam enters KUCA to be used asa 14 MeV neutron generator and test experiments
for the subcritical neutron source will be started
here. A beam course for the medical use isinstalled at the 2 MeV station. The injection of 20-134-

The 11th Symposium on Accelerator Science and Technology, Harima Science Garden City, 1997

Neutron Factory ProjectControl
RoomDTL
DTL

DAWReactorPhysics

Neutron Scattering
Cold Neutron Physics

High Energy
Neutron Physics

0Fig.2 Layout of Neutron Factory
MeV deuterons to KUR involves many problems
to be solved. It is most desirable to construct anew target system at the 300 MeV terminal.

3. Summary
In order to offer opportunities to utilize highenergy pulsed neutrons as well as low energy
steady neutrons, the KURRI has taken the firststep toward the realization of a multipurpose
neutron source involving particle accelenitors.
The nuclear hybrid system itself is very interesting
and worthwhile because it involves many technicalsubjects in both accelerator technology and nuclear
engineering. We hope that this proposal will be
discussed and polished up by those who areinterested in neutrons, accelerators and nuclearsystems.

204060m

References[1] S. Shiroya, Reports on Kyoto-University
Accelerator Projects, p.163(1997)(In Japanese)[2] "Neutron-Sources for Basic Physics andApplications". An OECD/NEA Report, ed. S.
Cierjacks, Pergamon Press, 1983.

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