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Journal of Radioanalytical and Nuclear Chemistry
Authors:
Bangfa Ni
,
Caijing Xiao
,
Donghui Huang
,
Hongchao Sun
,
Guiying Zhang
,
Cunxiong Liu
,
Pingsheng Wang
,
Haiqing Zhang
, and
Weizhi Tian

Abstract  

China Advance Research Reactor (CARR) at China Institute of Atomic Energy (CIAE), with a non-perturbed maximum thermal neutron flux of 1 × 1015 cm−2 s−1 at the center of active area, is one of the most powerful research reactors in the world. Three neutron channels have been allocated for conventional neutron activation analysis (NAA), thermal neutron prompt gamma activation analysis (PGAA) and cold neutron PGAA, respectively. Two irradiation tube systems are installed in the conventional NAA channel. One of them is for short irradiation with the rabbit size of diameter (Φ)19 × 40 mm, the other one is for long irradiation with the rabbit size of Φ39 × 70 mm. The medium temperature is about 45 °C and the thermal neutron flux is about 3 × 1014 cm−2 s−1 at sample positions. The flux gradient is expected to be very small according to the designed neutron flux distribution. Pneumatic systems are used for samples transfer. The speed of rabbits is designed to be about 20 m/s, and it takes 3 s to travel from irradiation position to detector. Three sets of gamma counting systems and one delayed neutron counting system are being equipped for routine analysis. They are designed for running continuously and automatically. And all the functions can be operated at laboratory or office through remote controlled computer. Software has been made domestically for spectrum peak search, concentration calculation with relative method and k0 method with interference corrections and some other functions for the convenience of users.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
Huang Donghui
,
Wang Pingsheng
,
Chen Xilin
,
Tian Weizhi
,
Ni Bangfa
,
Zhang Lanzhi
,
Zhang Guiying
,
Liu Cunxiong
, and
Liu Likun

Summary  

The half-life of 97Zr, used for the calculation of thermal/epithermal neutron flux ratio in k 0-NAA, is re-determined using three measurement systems with different pulse processing principles. The result of 16.755±0.013 hours clarifies the discrepancy between two widely used literature values, 16.744±0.011 and 16.90±0.05 hours. Different dead-time correction methods used on various measurement systems are evaluated. Factors influencing precise measurement of relative peak counting rates are discussed in time-series measurements over a dynamic range of 1000-fold radioactive intensities (10 half-lives).

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
Huang Donghui
,
Sun Hongchao
,
Ni Bangfa
,
Tian Weizhi
,
Zhang Yuanxun
,
Wang Pingsheng
,
Liu CunXiong
,
Zhang Guiying
,
Xiao Caijin
,
Zhang Haiqing
, and
Zhao Changjun

Abstract  

Sampling behavior of multielements for NIST SRM 2703, a marine sediment, was studied with sample sizes from 1 mg down to ng level by a combination of INAA, PIXE and SRXRF. On 1 mg sample size level, sampling behavior for multielements in NIST SRM 2703 and its parent SRM 2702 were comparatively characterized by using INAA combining with Ingamells model. Results showed that sampling uncertainties for 12 elements of both materials were found to be better than 1%, and those of four other elements in SRM 2703 better than in SRM 2702. At sample sizes not able to be accurately weighed (<1 mg), PIXE and SRXRF were used and the effective sample sizes estimated. Sampling uncertainties for nine elements were found to be better than 1% at sample sizes of tenth mg level, and those for six elements better than 10% on ng levels.

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