Fujita Technical Research
ReportNo.45 2009

Boron-Enriched Mortar Panel Applied to the Shielding Wall of theSpectrometer for Reducing Noise Neutron at the BL14 in J-PARC

Ken-ichi Kimura, Masaharu Kinno

Abstract
Boron-enriched mortar panels attached to PC (Precast Concrete) were applied to the shielding
structure of the spectrometer of beam line 14 in the J-PARC facility. In collaboration with J-PARC, twokinds of experiments were performed using cold neutron to confirm neutron shielding and reflection
performance. The results of the experiments for 19.6 wt% boron-enriched mortar showed a 10-foldimprovement in performance compared with the ordinary mortar. The thickness of the mortar in theapplied shielding material was 35mm, which was 1/3 thickness materials of the boracic acid resin
originally designed. This boron-enriched mortar enables more accurate measurement for most researchworks in J-PARC and could be applied to any facility where neutrons are generated.

§1. Introduction
anodes, magnets, structures of the earth core
Japan Proton Accelerator Research Complex,
called J-PARC[1][2],liquids, polymers, proteins, and medicines. Someis a new and exciting

accelerator research facility in Japan.

of the expected research results may include

The

understanding the functions and properties ofMaterial and Life Science Experimental Facility,

materials through the observation of quantum(MLF) is one of the main facilities in J-PARC, andeffects in solid state physics, understanding thehas the world’s highest intensity pulsed neutron

precise atomic structure of materials in theand muon beams in order to promote material

indispensable

science and life science[3].

biomolecular science for understanding life, andbaseofmaterialscience,

The neutron facility in MLF utilized a pulsed

behavior of the materials in high pressure andspallation neutron source based on a high power 3

high temperature for understanding earth science.

GeV proton synchrotron. This facility has 23

These researches are performed by detecting

neutron beam lines with different spectrometersreflected neutron from samples, which are set on

fields[4],the beam line inside of the spectrometer. One offor various researcheffects,

precisesuch as quantum

determination

ofatomic

the key factors is how to reduce noise neutron,

arrangement, surface science, biological molecules,

which come from various component materials forengineering applications, and so on. Thesethe facilities except samples. On the other hands,

researches are for various of subjects, which

the instruments including the spectrometer are

include super conducting materials, battery

covered in concrete or iron materials for theradiation shielding purpose. These shielding
materials can be source of the above unexpected

Keywords : Boron-enriched; Neutron; J-PARC;
PC ( Pre stressed concrete); accelerator

reflecting neutron.

－37－Fujita Technical Research Report

No.45

So, we developed a new type of shielding
materials, which reduced the rate ofreflection for the unexpected reflecting
neutron by about 10 times compared withordinary

materials

low-activation

based

concreteandonrelated

technologies[5][6], and applied them to theshielding materials in Beam Line 14(BL14) at J-PARC.
.

§2. Experiment
In order to estimate the reduction
performance

ofunnecessaryreflection

neutron from sources other than the target
samples,

twokindsofexperiments(transmission and reflection in a box) were
performed using JRR-3M (Japan Research

Fig.1 Geometry of the transmission experimentFig.2 Typical results for the transmission experiment－38－Boron-Enriched Mortar Panel Applied to the Shielding Wall of the Spectrometer for Reducing Noise Neutron at the BL14 in J-PARC

wt%. The horizontal axis indicates wave length,
which could be converted neutron energy, and thevertical axis indicates intensity. Each figure had
four curves for three different sample thicknesses
and direct beam.
From the three different curves shown in Figure
2, a macro cross section can be calculated for eachsample with different boron concentrations, which
was shown in Figure 3. The horizontal axis ofFigure 3 is the neutron energy and the vertical axis
is the macro cross section. This figure indicates thathigher boron concentration have higher macro crosssections. The rough curve for 19.6 wt%-enrichedsamples is caused by low intensity of transmission
Fig.3 Estimated macro cross section of each boron-enrichedsamples by transmission experiments

other three curves have higher intensities. This
figure shows that the 19.6 wt%-enriched data has

Reactor III in Tokai) [7], in collaboration withthe highest macro cross section for all neutronJ-PARC.

energies among the four smples, while thedifference to the 13.0 wt%-enriched data around a

2.1 Measurement of transmission

few meV is small and the tendancy of the curve forTransmission experiment is a common procedurethe 19.6%-enriched data is different from otherto discover the basic of shielding performanceagainstdata with the thicker samples in Figure 2, while theneutrontransmission.

Tenthree curves. This difference may cause low

different

intensity for the 19.6%-enriched samplse, so moreconcentrations of boron samples with three

data should be collected for better understanding.

different thicknesses were prepared for thetransmission experiments, and set shown as Figure

2.2 Evaluation to measure reduction of reflected

1. The neutron beam comes from left side of theneutrons

figure to the samples set in the center, and only

In the 2.1 section, the basic properties for thetransmitted neutron can be detected by the He-3transmission

neutron detector. The boron concentrations of theweretaken

fromthesimpleexperiment. However, the data required was thesamples were from 0.02 wt% to 40 wt%, and the

reduction of neutrons reflected by materials otherthickness were from 3mm to 25mm. The energy ofthan the target. So, a new type of experiment was

the neutrons for the experiment were mostly a few

carried out for the evaluation of the boron-enriched

meV, up to several tenth meV, which are calledmortar applied to the shielding wall of the“cold” neutrons, because of lower than “thermal”

spectrometer at the Beam Line 14 in J-PARC.

neutron in energy unit, which is equivalent to room

Measurement of only reflected neutrons wastemperature.

required in order to evaluate the reduction

Figure 2 shows typical results from theperformance. So 400mm cubic boxes with 300mm

experiments. The titles of the each figure indicate

cubic inner space and 50mm of wall thickness,the concentration of boron for the sample for thewhich were manufactured by 19.6% boron-enriched

test, which were 0 wt% (ordinary mortar) to 19.6

mortar and ordinary mortar, were prepared.

－39－Fujita Technical Research Report

No.45

Fig.4 Geometry for the experiment of the reduction performance of the reflected neutron

The neutron bean, which was thesameas

abovetransmission

Reflected neutron in the ordinary mortar

experiment, was guided inside anevacuated aluminum pipe in theReflected neutron in
19.6 wt% boron-enriched mortar box

box. The guided neutron went
through the inside of aluminum
pipe,

andirradiatedBackground neutron in the ordinary mortar box

thepolyethylene set at the end of thepipe facing the outside box. As

Background neutron in
19.6 wt% boron-enriched box

polyethylene is reflect-able material
to neutrons, some neutrons werereflected by the polyethylene set
facing the outside box wall toward
inside the box. These neutron werereflected more than one time to theinside wall, which was 19.6%
boron-enriched mortar or ordinary

Fig.5 Comparison of neutron reduction performance of 19.6 wt%
boron-enriched mortar to the ordinary mortar

mortar and were detected by thethe ordinary mortar. The peak value of the reflected

HE3 neutron detector, because the wall thickness

neutron for the boron-enriched mortar was 10 times

was 50mm and the neutron detector was set where

smaller than that for the ordinary mortar andthe neutron directly reflected by the polyethylene

background neutron for the boron-enriched mortar

could not be reached. Figure 4 shows the geometry

was also about 10 times smaller than that for thefor the experiment of the reduction performance ofordinary mortar. The two peaks in the figure show

the reflected neutron.

the quantities of the reflected neutrons and theThe measurements were carried out two times

difference of the two peaks shows the reduction

each (measurement of the reflected neutron andperformance of the reflected neutron for thebackground) for two materials, which were 19.6%

boron-enriched mortar to the ordinary mortar.

boron-enriched mortar and the ordinary mortar.

While background of the difference for the twoFigure 5 shows a comparison of neutron reduction

boxes was also indicated the reflection performance

performance of 19.6% boron-enriched mortar andof the neutron for boron-enriched mortar to the－40－

Boron-Enriched Mortar Panel Applied to the Shielding Wall of the Spectrometer for Reducing Noise Neutron at the BL14 in J-PARC

Fig.6 Sckematic veiw of the BL14 (dot circule indicate the spectromater sheilding which inside wall iscovered by boron-enriched mortar)§3. Apply to the BL14
The above evaluated 19.6% boron-enrichedmortar with a 3.5mm thickness was attached to aPC (Precast Concrete) wall with 750mm thickness
in order to satisfy the shielding requirement andthe reduction of the reflected neutron. This newly
developed PC plate, which can be call PC with theboron enriched mortar, was applied to the BeamLine 14 as a shielding structure for thespectrometer, which was called AMATERAS in the
Material and Life Facility, in J-PARC[8]. Figure 6shows the whole shielding structure, which includes
the shielding block around target (blue concrete
blocksontheright-handside),thebeamtransported shielding blocks (light pink concrete
blocks in the middle), and the shielding structure
for the spectrometer (circled by dash line in the left

Fig.7 design sketch of the spectrometer shieldingside).

ordinary mortar.

Figure 7 shows the design sketch for theThe neutron reduction performance of the 19.6%

spectrometer shielding structure, which has aboron-enriched mortar shows a 10-fold reduction incylindrical shape with 12 m diameter and 5 m

the peak value of the reflected neutrons andbackground.

Thisshowsthattheheight. All of the surface of the inside wall except

19.6%

floor, which area is about 200 m2, were weariedboron-enriched mortar walls have 10 times better

19.6%

performance in reducing the reflected neutronboron-enrichedmortar

with

3.5mm

thickness, which was originally designed 100mm

comparing to the ordinary mortar walls.

boracic acid resin.
The boron-enriched mortar, with a boron－41－Fujita Technical Research Reportconcentrationof

19.6w%,

canreduce

theNo.45

accelerator facilities, and so on.

unnecessary reflected neutron, which mainly comesfrom shielding wall, up to 1/10 and the thickness

Acknowledgements. The authors would like toexpress Dr. Kazuya Aizawa, Dr. Kenji Nakajimaand Dr. Mitutaka Nakamura, Japan Atomic Energy
Agency, who are the main member of acollaborating research works for evaluatingboron-enriched mortar. The authors appreciate Mr.
Madoka Itou, who is the director of the construction
works of the BL14 shielding and also Mr.
S.Yokosuka, Mr. T. Sasaya, Mr.H.Nishida,Mr.Y.Fujikura, and Mr.N.Katayose, who are themain contributors in the company for thedevelopment of the boron-enriched mortar.

can also reduce 1/3. This makes the inelastic andquasielastic scattering measurement in Bean Line
14 more accurate. The spectrometer of Beam Line
14[9] is called “AMATERAS –Cold Neutron
Disk-Chopper

Spectrometer”[7],

whichmainfeatures are new fast dick chopper, double chopper
spectroscopy with a coupled moderator source, andrepetition rate multiplication.

§4. Conclusion

References

The transmission of the cold neutron experiment
for the ten boron-enriched mortar samples wasperformed in JRR-3, in order to evaluate basic
shielding performance of the boron-enriched mortar.
The mortar of 19.6w% boron-enriched (19.6weight %), has best performance of the 10 samples.
To estimate the reduction performance of theneutronreflection,

anotherexperiment

http://j-parc.jp/index-e.html.
Yujiro Ikeda, “J-PARC status update” Nuclear
Instruments and Methods in Physics Research
A,Vol.600, Issue 1, pp.1-4, February 2009.
[3] http://j-parc.jp/MatLife/en/index.html.
[4] http://j-parc.jp/MatLife/en/roles/Neutron_Science.html.
[1][2]

wasperformed using a box consisting of 19.6%

Kinno M., Kimura K. and Nakamura T., “Raw Materials
for Low-Activation Concrete Neutron Shields”, Journal ofNuclear Science and Technology, Vol. 39, No. 12, 2002,
p.1275-1280.
[6] Kimura K. et al., “Low-Activation Reinforced Concrete
Design Methodology (8) - Fundamental Investigation for
Various Types of Low-Activation Concrete -, “19thInternational Conference on Structural Mechanics inReactor Technology, Toronto, Canada, 2007
[5]

K.Kimura et al. “Fundamental Study for the Reduction
Performance of Boron Contain Mortar to the Cold(Thermal) Neutron Flux”, JSNS2007, 2007.
[8] K.Kimura et al. “Development of Sheilding Precast
Concrete with High Concentration Boron Mortar”,
JSNS2008, 2008[9] http://j-parc.jp/MatLife/en/instrumentation/bl14/bl14.ht
ml.
[7]boron-enriched mortar, compared with the ordinarymortar. The neutron intensity reflected fromboron-enriched mortar box was about 10 times lessthan that from the ordinary mortar. This
experiment showed that the reduction of reflected
neutrons for the 19.6% boron-enriched mortar is 10

short comment
The developedboron-enriched mortar is very unique andshould be useful. So, I try to proceed to
distribute this material every possible
market related radiation field.

times better than that of the ordinary mortar.
Based on the above 2 undertaken in collaboration
withJ-PARC,

theperformanceof

theboron-enriched mortar was confirmed. So, this
newly developed boron-enriched mortar panel was
Ken-ichiKimuraattached to the PC, which was applied to theshielding structure of Beam Line 14 in MLF ofJ-APRC. The thickness of the boron-enrichedmortar was 35mm, which is 1/3 comparing to thedesigned thickness by boracic acid resin.
This boron-enriched mortar enables accurate
measurement for most research works in J-PARC,
and also can be applied at any facility where
neutrons are generated, such as nuclear facilities,－42－