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Nuclear Safeguards Techniques
Non-destructive Assaying for Attributes
of Fast Neutron Reactor’s Fresh Fuel
MENG Yan-tai, WANG Xiao-zhong, HE Li-xia, BAI Lei, SHAO Jie-wen, ZHU Li-qun
We have adopted active neutron coincidence method and γ-ray measurement method in order to
measure the attributes of fast neutron reactor’s fresh fuel. An improved uranium neutron coincidence
collar (UNCC) was used for measuring the
235U
enrichment distribution of the 2 pieces fuel assembles.
The measured results show curve’s trend is the same as the fact of distribution. Fig. 1 shows the
assembly’s neutron coincidence counting rate. We also used HPGe detector for uranium enrichment
measuring. The most relative deviation between measured value and declared value are about ±3%. Table
1 lists the measurement value and relative deviation. This experiment is the first time use NDA method for
measuring fresh fuel assembles’ attributes. It is a good basis in the future measurement.
Assembly’s neutron coincidence counting rate
Fig. 1
Table 1
Measured 235U abundance
235
235
U abundance/%
U abundance/%
Relative
No.
Relative
No.
Measurement
Declared
Measurement
Declared
value
value
value
value
069028
62.32%
64.4%
－3.2
069084
62.38%
64.4%
－3.1
069070
63.21%
64.4%
－1.8
069071
62.12%
64.4%
－3.5
069072
66.12%
64.4%
2.7
069075
63.81%
64.4%
－0.9
069076
62.68%
64.4%
－2.7
069080
61.57%
64.4%
－4.4
deviation/%
deviation/%
FUNDAMETAL AND APPLIED FUNDAMENTAL RESEARCH·Nuclear Safeguards Techniques
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Development of a Modual Radiological Portal Monitor
ZHANG Wen-liang, LI Xin-jun, ZONG Bo, GAN Lin, FANG Xin, ZHANG Li-ping,
ZHAO Rong-sheng, WANG Xiao-zhong, JIA Xiang-jun
Radiological portal monitor is used to detect gamma rays and neutron for personal and vehicle. It can
be installed at the access of the nuclear facility, airport, custom, railway station and other important place.
Large plastic scintillation detectors are used in the monitor to detect gamma rays emitted from
radioactive materials. And helium tube is used to detect neutron.
The detection principle, detection method, program and the structure of the radiological portal
monitor are introduced in this paper. The composition of this communication system and data acquisition
system are also described.
Development of a -ray Measurement System of Radioactive Wastes
HE Li-xia, SUI Hong-zhi, ZHOU Zhi-bo, GAN Lin, SHEN Ning, SHAO Jie-wen,
LIU Da-ming, GUO Bao-cheng, LI Zheng-shui
According to the criteria of radioactive wastes, intermediate and low-level radioactive solid waste
produced in nuclear fuel recycle must be characterized for near surface disposed. For this purpose, a
special -ray measuring system used for classifying low or medium-density drummed radioactive wastes
was developed. The system consists of three sets of high purity germanium detectors with multi-channel
analyzers. When the system works, waste drums rotate on axial and divided into three segments on radial.
The research and design for electronic control of the measurement system were carried out, the corrected
factories for -ray absorption in matrix as well as the activities analysis were also performed. The system
was calibrated and validated on a series of low enrichment uranium samples.
The results show that the uncertainty of activity measurement is less than 17%. This system will
redound to promote the availability in management and disposal of radioactive waste both for the state’s
administration department and nuclear facilities.
Upgrade of Physical Design for Removable Segmented Gamma Scanner
HE Li-xia, WANG Zhong-qi, SUI Hong-zhi, GAN Lin
Segmented Gamma Scanner is one of the most important non-destructive assay instruments, which is
used to quantify radioactive isotopes in low or median-density matrix. The present research concerns in its
physical design. The mainframe consists of three parts, such as transmission assembly, sample position
system and detector assembly. Transmission source shielding will be made from tungsten-ferronickel; this
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Annual Report of China Institute of Atomic Energy 2006
kind material is more effective than lead. Choosing integrated digital spectrum analyzer to replace NIM
instruments; the integrated, all-in-one package greatly simplifies system installation and setup. The SGS
software will be developed on windows technology and has self-control functions. The code will be
replanted in any PC. So the system will be available and its performance will be largely extended.
Radioactive Waste Information Management System
BAI Lei, LIU Fu-guo, YAN Xiao, QI Guang-mao, LIU Ning, GAN Lin, LIU Da-ming
According to the requirement and current situation of national industrial radioactive waste
management and disposal, present work develops drummed radioactive waste information management
system based on network. The system may provide effective real-time management both for
administration and enterprise. And the -detecting classification facility of barrel radioactive waste is also
prepared.
This system used VB as a development platform, and SQL Server 2000 as the background database.
The main functions of this system are as following:
1) Computerize radioactive waste disposal technological process management;
2) Memory and inquiry for radioactive waste disposal management data;
3) Bar code management traced automatically all the flow;
4) Interface with the other management system and equipment.
Analysis of Uranium Enrichment in Environment Samples
Using HPGe γ-ray Spectrometry
LI Jian-hua, JIN Hui-min, CHANG Zhi-yuan, WANG Chen
In this work a method for determination of uranium enrichment in environmental samples was studied
and the minimum detectable activities of 235U in environmental samples (including soil, water, swipe)
using HPGe γ-ray spectrometry were determined. Eq. (1) is used to calculate the enrichment of uranium in
the samples. G was obtained through Eq. (1) or Eq. (2) by measuring a working standard or reference
material in which the uranium enrichment is known. After determining the sample, the enrichment of
uranium is calculated.
S 5 / S8
(1)
F5 =
G + S 5 / S8
G=
Where the subscripts “5” and “8” stand for
Bγ,5e5T1/ 2,8
(2)
Bγ,8e8T1/ 2,5
235U
and
238U,
respectively; S is the net area of 186 keV and
1 001 keV peaks. B is emission probability; ε is detection efficiency; T1/2 is its half life.
For some simulated environmental samples in each which contains about 100 mg uranium with about
FUNDAMETAL AND APPLIED FUNDAMENTAL RESEARCH·Nuclear Safeguards Techniques
193
20% 235U, the uranium enrichment determined by HPGe -ray spectrometry is in agreement with one by
mass spectrometry.
Age-Dating of Highly Enriched Uranium (HEU) by γ-Spectrometry
LU Xue-sheng, LIU Da-ming, LIU Guo-rong
The definition of age of a uranium sample is the time passed since it has been chemically separated
from its daughter nuclides and enriched.
For the fissile material cut-off treaty determining the age of HEU is important for distinguishing
newly produced materials. In addition, determining the date of production of a HEU sample can help the
safeguards inspectorate to decide whether the nuclear material originates from excess weapons-usable
materials or it is freshly produced.
We presented a non-destructive, gamma-spectrometric method for uranium age determination which
is independent of the physical form and geometrical shape. The method is based on measuring the
daughter/parent 214Bi/234U activity ratio by using intrinsic efficiency calibration. The investigated sample
is U3O8 powder with 90% of 235U. The Uranium-age obtained by this gamma-spectrometric method is in
agreement with the results by using destructive method based on determining the daughter/parent
231Pa/235U isotope ratios.
Study on Analysis of Isotopic Ratio of Uranium
in Uranium-Bearing Particle by FT-TIMS
SHEN Yan, ZHAO Yong-gang, GUO Shi-lun, CUI Jian-yong1, LIU Yu-ang1
(1 Beijing Research Institute of Uranium Geology)
Environmental sampling is an important technique for international nuclear safeguards. The isotopic
compositions of uranium-bearing particles must be analyzed in uranium enrichment facility for safeguards.
Many techniques were used in analysis of uranium containing particles, and FT-TIMS (fission trackthermal ionization mass spectrometry) is one of them.
Methodology of FT-TIMS is studied in the analysis of uranium-bearing particles. The method
consists of (1) searching for rare uranium containing particles by fission track technique; (2) transferring
single particle by micro-manipulator from the sample to a filament used in TIMS; and (3) uranium
isotopic ratio determination by TIMS.
In the study of searching for uranium-bearing particles by fission track, choosing of sample mat and
fission track detector, accurate locating, choosing of irradiation flux and etching condition of fission track
detector were explored in the work. The method can offer an average deviation of less than 5 µm in
locating the position of uranium containing particles by fission track.
In the study of transferring microscopic particles, the techniques concerns in the transfer of particles
from samples to filament of TIMS was investigated, about 90% particles would were successfully
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Annual Report of China Institute of Atomic Energy 2006
transferred.
In TIMS analysis, sample-spreading technique, origin of background, estimation of background and
emendation method were studied. The intensity of uranium ion was increased about 10 times and the
precision of 235U/238U isotopic ratio is better than 0.7%, owing to using graphite powder as ionization
enhancer. Under the existence of background, the accuracy is about 1% for particles of about 2 m in
diameter. For smaller particles, the accuracy is about 5% or higher.
Experimental Study on 14 MeV Neutron Interrogating and Identifying
Uranium Metal, Uranium Oxide and Uranium Fluoride
LIU Guo-rong, LI An-li, WANG Zhi-qiang, LUO Hai-long, WANG Chen,
LU Xue-sheng, LI Chun-juan, LI Jing-huai
In order to identify the chemical form of uranium material in a sealed container, the experiments
have been done on 5SDH-2 type 2×1.7 MV tandem accelerator，which used 14 MeV neutrons to
interrogate materials, such as uranium metal, uranium oxide, and uranium fluoride.
There are three nuclear reactions of 14 MeV neutrons:
16
s = 0.1 b
O(n, n')16 O*
-
16
O(n, p)16 N ¾ β¾®
19
F(n, α)16 N ¾ β¾®
-
16
16
O*
s = 33 mb
T1/2 (16 N)=7.13 s
O*
s = 40 mb
T1/2 (16 N)=7.13 s
where 16O* de-excitations radiate 6.13 MeV -rays.
The purpose of this experiment is to judge whether measuring the 6.13 MeV  rays can identify the
chemical form of uranium material.
The experimental arrangement is shown in Fig. 1. The accelerated deuteron beam bombards T-Ti
－
target and generates 14 MeV neutrons with the intensity of 108 s 1. The distance from target to sample is
26 cm, and the distance from sample to the surface of HPGe -detector is 16 cm. Three samples, such as
UF4 (180 g), UO2 (100 g), and uranium metal (3 000 g) have been used in the experiments.
Fig. 1
Experimental arrangement
1——Sample; 2——Deuteron beam; 3——T-Ti target; 4——α-detector; 5——Pb shielding;
6——HPGe -detector; 7——Pb collimator; 8——absorber plates
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195
Measurements show that the 6.13 MeV  peak is strong in the -spectrum of UO2 sample, but it is not
observable in the -spectrum of UF4 sample. The counting rate of 6.13 MeV -peak of UO2 sample per
unit mass is more than that of UF4 sample per unit mass by a factor of ten. 6.13 MeV -peak does not
appear in the -spectrum of the uranium metal sample. The conclusion of this experiment is that to
distinguish UO2 with 6.13 MeV -rays is feasible, but it is difficulty to distinguish UF4.
Studies on Accurate Measurement of Isotope Ratio of Trace Plutonium
in Uranium Matrix by Multi-collector Inductively
Coupled Plasma Mass Spectrometry
LI Li-li, LI Jin-ying, ZHAO Yong-gang, ZHANG Ji-long, WANG Tong-xing
It is not only significant for non-proliferation and the quality control of uranium product but also for
identifying approximately the source of uranium by accurately measuring the abundance ratio of
plutonium isotopes in uranium product obtained by spent fuel reprocessing process. It has been full of
difficulties to analyze accurately the abundance ratio of trace plutonium in uranium product because of the
low content of plutonium (less than 1 ng/g).
It has been systemically studied that the main factors affect the measurement of isotope ratio of trace
plutonium by MC-ICP-MS which include the sensitivity, resolution, selection of mode of ion extraction,
elimination of background and interference, the system of sample introduction etc. These parameters are
studied and optimized. The emendation for mass bias of samples in MC-ICP-MS is explored. The velocity
of nebulizer and the axial position of torch are the main factors which affect the sensitivity of
MC-ICP-MS. The resolution is assigned at 300. The hard mode of ion extraction is adopted when the
isotope ratio of trace plutonium is measured and the Aridus Desolvating Nebulizer System is applied. To
＋
the measurement of M/Z=239 by MC-ICP-MS, the interference of 238UH caused by the combination of
238U and H+ in plasma and the tailing of 238U is produced when the abundance ratio of trace plutonium in
uranium matrix is measured by different sample introduction systems. The ratio of counts in M/Z=239 and
＋
M/Z=238 is measured by natural uranium solutions with different concentration. The average of 238UH /
＋
－
－
U ratio is 8.9×10 5 and 3.6×10 4, respectively to the uranium solutions with the concentration between
－
－
－
－
1 ng·g 1 to 500 ng·g 1 and 1 pg·g 1 to 1 ng·g 1. The Aridus Desolvating Nebulizer System increase the
sensitivity of MC-ICP-MS by decuple and the precision is improved from 2% to 1% for the plutonium
－
sample with ng·L 1 level. The possibility has been validated initially that the mass bias of plutonium can
be corrected from the analysis of reference materials of uranium or the other reference materials of
plutonium under the circumstance of the corresponding reference materials of plutonium lacks.
The abundance ratio of trace plutonium in reprocessed uranium is measured by MC-ICP-MS after
separation using extraction chromatography. The combined relative uncertainty for plutonium
－
measurement is better than 5%. The measuring method for ng·g 1 level plutonium isotope ratio is
established.