CO10-1

Activation Analysis for Soils of Hiroshima･Nagasaki City and Gamma-ray
Exposure Due to Neutron-induced Radionuclides by Atom Bomb

S. Endo, K. Shiraishi, Y. Taguchi, T. Imanaka1,S. Fukutani1, M. Hoshi2 and K. Shizuma
Graduate School of Engineering, Hiroshima University
2
Research Reactor Institute, Kyoto University
3RIRBM, Hiroshima University
INTRODUCTION: For early entrance survivors inHiroshima and Nagasaki atomic bomb (A-bomb), radiation doses from activated materials induced by theA-bomb neutrons are dominant. For estimation of suchdoses, element compositions of environmental materials
such as soil and rubbles are necessary. Especially Sc density in soil is important for estimating radiation doses at
the time of a few 10 days after explosion because 46Sc
has the half-life of 84 days. However, few data of Sc
density in soil are available in both of Hiroshima andNagasaki cities. Purpose of this study is evaluation of Sc
density in soil and the uncertainty using activation analysis.

[2] Roesch, W. C., Eds. (1986) U. S.—Japan Joint Reassessment of Atomic Bomb Radiation Dosimetry in Hiroshima and Nagasaki. Vols. 1 and 2. Radiation Effects
Research Foundation.
[3] S. Endo et al. (2013) Neutron activation analysis forsoils of Hiroshima City and Plaster under roof-tiles ofOld Hiroshima House, Revisit the Hiroshima A-bombwith a Database Vol. 2, Hiroshima City 2013, ISBN:
978-4-9905935-1-3,9-14
Table 1. Averaged values of element concentration insoil and DS86 for Nagasaki City [1].
Elementconcentration（ppm）

DS86Values（ppm）
Hypocenter

Nagasaki Univ.

Na

6120

±

4020

7890

7500

Mg
Al13700
95500

±±

3120
22000

8200
99600

7350
97000KSc6320
19.5±±3620
3.0764020754020Ti
V6040
190±±2040
565860
167

6320
171Cr
Mn

178
1570

±±84632

151
1310

152
1260

FeCo

59000
26.1±±10900
7.557300
2358800
22Ni
Rb

55.4
29.4±±

26.3
15.9

5370

5468

Sr
Zr

178
234±±6176

134
126

124
127

In
Cs

0.054
2.69±±0.017
0.80

Ce
Sm

34.6
4.9±±8.1
1.8Eu
Gd

0.75
5.12±±0.21
1.31--

Dy
Yb

3.73
2.11±±1.510.61--

HfTa

5.30.91±±0.740.23

6.0
0.6

6.1
0.5

Th

6.3

±1.2

7.0

7.2

採択課題番号 24006 広島・長崎原爆中性子による誘導放射能評価のための組成分析（広大院・工）遠藤 暁、田口優太、静間 清、（広大・原医研）星 正治（京大・原子炉）今中哲二、福谷 哲

共同通常

EXPERIMENTS: Soil samples were taken from 11locations within 5 km from A-bomb hypocenter at Nagasaki city. The soil samples were dried by an oven at 120
degrees for an over-night. The dried samples were sieved
through a 2-mm mesh to remove pebbles and plant remains. The sieved samples of about 10 g were grained tofine mesh by a mortar for activation analysis. The soilsamples and reference rock sample of JA-1andJB-1[1]were activated in Kyoto University Reactor(KUR). Element compositions of soil samples were obtained by comparing counting rates of each identified
radionuclide by Ge-detectors with those from reference
rocks.
RESULTS: Twenty six element compositions including
Al, Mn, Na and Sc are obtained by the activation analysis
as listed in Table 1. The obtained element compositions
are compared with values used in Dosimetric System
1986 (DS86) [2] and found roughly the same as the reported values in DS86. Mn and Sc density in Nagasaki
soil was estimated to be 1570±632 (ppm) and 19.5±3.01(ppm), respectively. These values are relatively higher
than 517±67 (ppm) and 5.12±0.59 (ppm) of Hiroshimasoil [3], respectively. It was found the unevenness of Sc
density in soils for 11 location of Nagasaki City is about
15%. This results shows that the Sc contribution for dosein air at a few 10 days after explosion at Nagasaki City isrelatively higher than those at Hiroshima City.

-4.0

4.0

43
3.943
4.0

1.5

1.6

REFERENCES:[1] Imai, N.et al. (1995) 1994 compilation of analytical
data for minor and trace elements in seventeen GSJ geochemical reference samples, "igneous rock series",
Geostandards Newsletter 19: 135-213.

CO10-2

Damage of Semiconductor Equipment by Radiation Exposure

J. Takada, K. Tanaka and Y. Sakurai1
Center for Medical Education, Sapporo Medical University
1
Research Reactor Institute, Kyoto University

INTRODUCTION:
Quantitative evaluation of theradiation effect on the semiconductor equipment is important in estimating the damage of the nuclear disasters
and planning how to defense the damage [1]. Our grouphas been working on evaluating this radiation effect [2].
In 2012, the radiation damage to condenser-resistor (CR)circuit was investigated.

EXPERIMENTS: The irradiation was performed withKyoto University Research Reactor Institute Heavy Water Neutron Irradiation Facility (KUR-HWNIF), at a
power of 1 MW. The utilized mode was the standard mix
neutron irradiation mode (OO-0000-F). As semiconductor equipment, digital timers (A&D corporation,AD-5712GR) were utilized. The digital timers wereplaced at varied distances of 0, 20, 50, 100, and 190 cm
from the collimator aperture as shown in Figure 1. At
each distance, two digital times were arranged. Irradiation was performed for 62 minutes.

of 320 mGy/h) had a problem, i.e., each of them was 40
seconds and 180 seconds ahead of correct time, respectively. On the other hand, at 0 cm (646 mGy/h at 667mGy), one timer was 1000 seconds ahead, the other did
not show any characters. The latter could not be restarted
or reset after the irradiation, while the others worked
correctly.
Assuming the threshold for the timer to have a problem
to be 173 mGy, the dose at 50 cm, exhibited value aheadof the correct time was 40 and 180 seconds at the excessdose of 158 mGy (20 cm), and 1000 seconds at the excess dose of 494 mGy (0 cm). The correlation between
both values can not be concluded so far.
Table 1. Absorbed dose by irradiation
Distance toDose (mGy)collimator
ThermalEpithermal
aperture (cm)neutronneutron01.28 × 102 1.38 × 101
205.75 × 101
6.48
150
2.56 × 10
3.01
100
9.93
1.17
190
2.25
2.18 × 10-1
Table 1. (cont.)
Distance tocollimator aperture (cm)02050
100190Fastneutron
2.30 × 102
9.40 × 101
2.68 × 101
3.32
4.99 × 10-2

Dose (mGy)Gammarays
Total
2.96 × 102
6.67 × 102
1.73 × 102
3.31 × 102
1.17 × 102
1.73 × 102
17.74 × 10
9.18 × 101
12.41 × 10
2.66 × 101

SUMMARY: The digital times irradiated showed abnormal operation at doses of 331 mGy or more (neutron
contributions at 30 to 35 %). The exhibited time ahead of
the correct time and the irradiated dose have not beenconcluded as to their relationship. However, the frequency and amount of abnormality possibly works as an index
of the exposure to human body in nuclear disaster.
Fig. 1. View of irradiation port
RESULTS: Table 1 shows the dose irradiated. Thevalues correspond to the dose to human tissue. At distances of 50 cm or more, the times worked correctly,
while the USB memories were out of order at similardoses [2]. The times at 20 cm (331 mGy at the dose rate

REFERENCES:[1] J. Takada, Nuclear hazards in the world, Kodansha(Tokyo) and Splinger (Berlin), (2005) 1-133.
[2] K. Tanaka, Y. Sakurai, J.Takada, Radiation Protection
Medicine, 8 (2012) 47-50.

採択課題番号 24078
核放射線照射による電子機器の誤作動の検証（札医大・医療人育成セ）高田純、田中憲一（京大・原子炉）櫻井良憲

共同通常Study on Neutron Response of Criticality Accident Alarm System Detector toQuasi-Monoenergetic 24 keV Neutrons

Japan Atomic Energy Agency
1Research Reactor Institute, Kyoto University

INTRODUCTION: A criticality accident alarm system (CAAS) is a purpose-built radiation monitor intended
to provide an immediate evacuation signal in the case ofan accidental criticality in order to minimize personnel
exposure. The latest model of the CAAS, recently developed and installed at the Tokai Reprocessing Plant of theJapan Atomic Energy Agency, consists of a plastic scintillator combined with a cadmium-lined polyethylene
moderator and responds both to gamma rays and neutrons[1]. To evaluate the detector response to 24 keV quasi-monoenergetic neutrons, an experiment was performedat the B-1 facility of the Kyoto University Research Reactor.
EXPERIMENTS:
The B-1 facility consists of45-cm-thick iron and 35-cm-thick aluminum filters builtin a radial beam tube of the reactor and provides an intense beam of 24 keV neutrons transmitted through ‘resonance window’ in the cross-sections of iron and aluminum [2]. The 10 cm × 10 cm square opening at the beamexit is smaller than the dimension of the CAAS detector;
therefore, a wooden platform attached to the motion
mechanism of a motor-driven linear actuator was constructed and the CAAS detector mounted on the platform
was horizontally moved across the neutron beam along
the line perpendicular to the beam axis and 100 cm distant from the beam exit. A neutron rem counter (Studsvik2202D) and an energy-compensated GM counter (FWTGM-1), each spaced 60 cm and 30 cm from the CAASdetector, were also mounted on the platform and irradiated simultaneously to evaluate the reference dose rates
of neutron and gamma ray, respectively. The neutron response of the CAAS detector was derived by dividing theneutron-induced net reading, deduced by subtraction of
the estimated gamma-ray fractional reading based on thegamma dose rate, by the reference neutron dose rate. Thereactor was operated at 1 MW.
RESULTS: Fig. 1 compares readings of the CAAS detector, the 2202D, and the GM-1 as a function of thetraverse distance from the beam center (0 cm). Full travel
was 60 cm: 0 to +60 cm for the CAAS, −30 to +30 cm
for the GM-1, and −60 to 0 cm for the 2202D. The curvemeasured with a physically small GM tube represents theactual dose profile, showing that the entire neutron-sensitive region (i.e., moderator) of the CAAS detector was covered with the neutron beam over half thepeak intensity.
Fig. 2 exhibits the energy dependence of the relative neutron absorbed dose rate response of the CAAS detector.

The experimental data obtained in this study is plotted
together with the data obtained with a 252Cf neutron
source [3]. Also plotted are the computer–calculated responses for monoenergetic neutrons. A comparison
showed that experimental data at 24 keV reasonably
agreed with those obtained with previous calculations.
The agreement between the experimental and calculated
responses gave strong experimental support to the calculated response functions over the entire energy range
from thermal to a few MeV.
1.2
2202DGM-1nγ−CASCAAS

1.0

Readings (Arb.)

N. Tsujimura, T. Yoshida and H. Yashima1

0.8
0.6
0.4
0.2
0.0-60-30

03060

Distance from the beam center (cm)Fig. 1. Readings of the CAAS detector, the 2202D,
and the GM-1 across the neutron beam, scannedalong the line perpendicular to the beam axis and100 cm distant from the beam exit.
101

Neutron absorbed dose response
137(normalized to Cs γ response)

CO10-3100

10-1
Calculations
252
CfThis work

10-2
10-8

10-6

10-4

10-2100

102

Neutron energy (MeV)

Fig. 2. Neutron absorbed dose rate response of theCAAS detector as a function of the neutron energy.
REFERENCES:[1] N. Tsujimura and T. Yoshida, Prog. Nucl. Sci.
Technol., 1 (2011) 202-205.
[2] K. Kobayashi, T. Yoshimoto, Y. Fujita, M. Utsuro, andH. Utsumi, Reactor Dosimetry: Radiation Metrology
and Assessment, ASTM STP 1398 (2001) 183-190.
[3] N. Tsujimura and T. Yoshida, Prog. Nucl. Sci. Technol.
( in press).

採択課題番号 24107 24keV 準単色中性子に対する臨界警報装置の中性子感度の実験的評価 共同即時（原子力機構）辻村憲雄，吉田忠義（京大・原子炉）八島浩