China Institute Of Atomic Energy Research Articles

Transient simulation code development of primary coolant system of Chinese Experimental Fast Reactor

Chinese Experimental Fast Reactor (CEFR) is a 25MWe sodium cooled, pool type reactor, which was built at the China Institute of Atomic Energy in Beijing as the forerunner to the first-stage of Chinese fast reactor development plans. In order to understand the response of the Primary Coolant System (PCS) to various transients and train the operators a dynamic model using basic energy and momentum equations was developed with some assumptions. Heat transfer models for reactor core and intermediate heat exchanger were also included. Subroutines were developed to calculate the thermal properties, friction coefficients and heat transfer coefficients of liquid sodium. Gear’s method was applied to solve the dynamic model. A transient analysis code named THPCS (Thermal–Hydraulic code of PCS) was developed and is independent of the design and safety analysis codes. Three typical events, such as loss of one primary pump, unprotected transient overpower and accidental closure of primary pump check valves were chosen and investigated. The prediction results of the code agree well with those of the final safety analysis report of CEFR. A fourth postulated accident, station blackout without scram and loss of all heat sink, was also analyzed to show the ability of the code, which is more serious than the former. The transient simulation code developed in this paper will be useful for the safety operation of CEFR.

Recent progress in AMS measurement of 182Hf at the CIAE

In order to improve the accuracy of accelerator mass spectrometry (AMS) measurement for 182Hf/180Hf, a series of measurements have been taken in the AMS laboratory at the China Institute of Atomic Energy (CIAE). The major ones include the instantaneous monitoring of 180HfF−5 current, testing the stability of transmission, the alternate measurements of an unknown sample and standard, and the origin identification and minimization of background 182W. The experimental details and the improvement in the measurement accuracy, as well as some useful suggestions for better satisfying the requirements of certain practical applications, are presented in this paper.

Progress of Nuclear Physics in CIAE

The research activities in China Institute of Atomic Energy (CIAE) are mainly performed in Beijing National Tandem Accelerator Laboratory (BNTAL), a national user facility in the Department of Nuclear Physics (DNP). During recent years, the main machine is HI-13 tandem accelerator, which is delivering the stable heavy-ion beam with energy of up to 15 MeV/q. It annually provides beam time for about 50 experiments with about 4,000 hours. The beam time sharing by research area is as follows: nuclear reaction 24%, nuclear structure 23.5%, nuclear data 18%, and application 34.5%. In the above research, the annually delivered beam time for outside users are 1,200 hours. The users range from application institutions, universities, to research institutes. The total number of the annual publication of SCI papers are more than 50. About 100 foreign visitors visited our Lab, and more than 50 staff members visited abroad each year.

50 mm Diameter digital DC/pulse neutron generator for subcritical reactor test

A 50mm diameter digital DC/pulse neutron generator was developed with 25mm ceramic drive-in target neutron tube. It was applied in the subcritical reactor test of China Institute of Atomic Energy (CIAE). The generator can produce neutron in three modes: DC, pulse and multiple pulse. The maximum neutron yield of the generator is 1×108n/s, while the maximum pulse frequency is 10kHz, and the minimum pulse width is 10μs. As a remote controlled generator, it is small in volume, easy to be connected and controlled. The tested results indicate that penning ion source has the feature of delay time in glow discharge, and it is easier for glow discharge to happen when switching the DC voltage of penning ion source into pulse. According to these two characteristics, the generator has been modified. This improved generator can be used in many other areas including Prompt Gamma Neutron Activation Analysis (PGNAA), neutron testing and experiment.

Improvement on AMS Measurement of 236U at CIAE

In order to improve the detection efficiency and sensitivity for 236U measurement at China Institute of Atomic Energy (CIAE) accelerator mass spectrometry (AMS) system to meet the requirement of some applications, we present some new improvements of the measurement method for AMS measurement of 236U at CIAE AMS. The main features of the method include: (i) measurement optimization; (ii) improvement of the TOF time resolution ∼500ps. Based on these improvements, the sensitivity is ∼10−11 for 236U/238U in the present work, higher than before (236U/238U∼5 × 10−10).

High-spin structures in the139Pr nucleus

Background: ${}^{139}$Pr is located in a transitional region of neutron number close to the $N=82$ shell. The study of its high-spin states and collective bands is important for systematically understanding the nuclear structural characteristics in this region.Purpose: To investigate the high-spin levels and to search for oblate bands in ${}^{139}$Pr.Methods: The high-spin states of ${}^{139}$Pr have been studied via the reaction ${}^{124}$Sn(${}^{19}$F,4$n$) at a beam energy of 80 MeV. The experiment was carried out at the HI-13 Tandem Accelerator at the China Institute of Atomic Energy (CIAE). The data analysis was done by using the $\ensuremath{\gamma}$-$\ensuremath{\gamma}$ coincidence method.Results: The level scheme of ${}^{139}$Pr has been expanded with spin up to 45/2$\ensuremath{\hbar}$. A total of 39 new levels and 45 new transitions are identified. Four collective band structures at high-spin states have been newly established. From systematic analysis, one of the bands is proposed as a double decoupled band; two bands are proposed as oblate bands with $\ensuremath{\gamma}\ensuremath{\sim}\ensuremath{-}{60}^{\ensuremath{\circ}}$; another band is suggested as an oblate-triaxial band with $\ensuremath{\gamma}\ensuremath{\sim}\ensuremath{-}{90}^{\ensuremath{\circ}}$. The other characteristics for these bands are discussed.Conclusions: A new level scheme in ${}^{139}$Pr has been established and the collective bands at high spin have been identified. The result shows that the strong oblate shape-driving effect is caused by neutrons at the high-spin states in ${}^{139}$Pr.

AMS Measurement of 36Cl with a Q3D Magnetic Spectrometer at CIAE

The ratio of 36Cl/Cl can determine the exposure age of surface rocks and monitor the secular equilibrium of 36Cl of sedimentary and igneous rock in groundwater. Due to the uncertainty effects of different chemical separation processes for removing 36S, there is a high degree of uncertainty in 36Cl accelerator mass spectrometry (AMS) measurements if the ratio of 36Cl/Cl is lower than 10−14. A 36Cl AMS higher sensitivity measurement has been set up by using a ΔE-Q3D method at the China Institute of Atomic Energy (CIAE). The performances of ΔE-Q3D method for 36Cl-AMS measurement had been systemically studied. The experimental results show that the ΔE-Q3D method has a higher isobar suppression factor. Taking advantage of direct removing 36S, the sample preparation can be simplified and the uncertainty effects of different chemical separation processes can be reduced in 36Cl AMS measurements.

Magnet Design for a 70 MeV ${\rm H}^{-}/{\rm D}^{-}$ Dual Accelerating Particle Cyclotron

A 70 MeV cyclotron for radioactive ion beam production and other applications has been designed at China Institute of Atomic Energy (CIAE). The main challenge of the magnet design for this particle machine lies in the needs of two isochronous magnetic fields to accelerate H <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-</sup> and D <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-</sup> with charge-mass ratios of 1 and 0.5 respectively. The required isochronisms are achieved by installing removable shims and adjusting the RF frequency. The magnetic fields and beam dynamics design results for both H <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-</sup> and D <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-</sup> beams are described in this paper. The analysis on field imperfections caused by the magnet deformation and the effects of annealing on magnetic properties of materials, are also outlined.

Magnet Design and Fabrication of CYCIAE-14, a 14 MeV PET Cyclotron

In line with the increasing demand for PET cyclotrons in China, the construction of a 14 MeV high intensity compact cyclotron, CYCIAE-14, has been proposed at China Institute of Atomic Energy (CIAE) in 2010 and is scheduled to be finished within two years. The fabrication is in smooth progress, with a majority of the devices ready in place for installation. As a critical part of the cyclotron, the main magnet development is of paramount importance to the successful development of the machine. At present, the main magnet design and fabrication has been accomplished. The physics design of the main magnet, which enables the realization of strong focusing by adopting a 4-sector structure with variable hill gap, will be emphatically introduced in the paper. Meanwhile, the engineering techniques applied to the fabrication will also be presented, in particular the technical challenges encountered in the process. Based on the accomplishment of two sets of main magnets, six more sets of main magnets will be fabricated.

Quest for Chirality in 107Ag

High spin states in 107Ag have been studied via the 100Mo(11B, 4n)107Ag reaction at a beam energy of 60 MeV on the HI-13 tandem accelerator at the China Institute of Atomic Energy. By analyzing the gamma-gamma coincidence and their DCO ratios, a new level scheme of 107Ag is presented. The structures for the newly constructed bands are briefly discussed and tentatively assigned to be chiral doublet bands.

High Spin Structure in 106Pd

The high spin states of 106Pd have been populated through the 100Mo(11B, 1p4n)106Pd reaction using a beam energy of 60 MeV provided by the Beijing HI-13 tandem accelerator at China Institute of Atomic Energy. By analyzing the γ-γ coincidence relation and DCO raios of transitions, 3 rotational bands with 13 new states and 22 new γ transitions belonging to 106Pd were constructed. Bands 2 and 3 with negative parity were supposed to build on the νh11/2g7/2 and νh11/2d5/2 configuration, respectively.

Separation of 95Y from fission products by SISAK and extraction chromatography technique

Radioactivity measurement of short-lived nuclides is the basis of decay data measurement, which requires rapid separation and purification of the interested nuclides from complicated fission products. A rapid separation system based on SISAK and extraction chromatography technique was established to isolate 95Y, which half-life is 10.3 min. With the best conditions studied in this paper, 95Y was separated successfully from complicated fission products under the mini-reactor in the China Institute of Atomic Energy. Decontamination factors to other nuclides except 94Y are higher than 2 × 103.

A first attempt to measure 92Nb/93Nb ratios with Accelerator Mass Spectrometry

An Accelerator Mass Spectrometry (AMS) method for the measurement of the long-lived radionuclide 92Nb has been established at the HI-13 Tandem Accelerator of the China Institute of Atomic Energy (CIAE). Niobium powder mixed with PbF2 by a ratio of 1:2 (in mass) was used as the cathode material. Atomic anions of Nb− were extracted from a Cs-beam sputter source. The terminal voltage of the tandem accelerator was 8.5MV. Nb13+ ions were selected after terminal foil stripping. A multi-anode gas ionization chamber was used for the particle detection. The total suppression factor of the two major interfering isobars, 92Zr and 92Mo, was about 103. A detection limit of about 10−11 was achieved for 92Nb/93Nb ratio measurements on a blank sample.

Large projects at the accelerator mass spectrometry facility at the China Institute of Atomic Energy during the last 12 years

Progress made by the Accelerator Mass Spectrometry (AMS) facility at the China Institute of Atomic Energy (CIAE) since 1999 is reported in terms of system upgrades, exploration with other long-lived isotopes, advancements in methodology, and new applications.

Further study on highly sensitive AMS measurement of 53Mn

The AMS facility at China Institute of Atomic Energy has been equipped with a ΔE-Q3D detection system for the measurements of 53Mn. While the sample material of MnO2 and the extraction ions of MnO− were used previously in AMS measurement of 53Mn with fairly good results, a method has recently been developed with the extraction of MnF− from ion source using MnF2 and MnO2+PbF2 as sample materials. As a result, a sensitivity of 10−14 (53Mn/Mn) has been achieved. Compared with the original MnO−/MnO2 approach, the method of MnF− extraction, combined with ΔE-Q3D detection technique, demonstrated an improved sensitivity for AMS measurement of 53Mn.

Experimental development on the 18 mA, H− multi-cusp ion source at China Institute of Atomic Energy

The ion source is one of the key devices for the high-intensity cyclotron, which exerts influence on the beam intensity and applications of the machine. The H(-) multi-cusp ion source developed at China Institute of Atomic Energy has been used to perform experimental study on beam intensity and emittance versus the bias voltage, arc power, lens voltage, and pressure of the ion source. Up to now, 18 mA H(-) ion beam with emittance of 0.93 πmm mrad (four times RMS normalized emittance) was obtained from this ion source through the in-depth study and optimization on some essential factors affecting the beam intensity and quality. The paper will present the experimental study on the ion source as well as the beam test results.

Development of a compact filament-discharge multi-cusp H− ion source

A 14 MeV medical cyclotron with the external ion source has been designed and is being constructed at China Institute of Atomic Energy. The H(-) ion will be accelerated by this machine and the proton beam will be extracted by carbon strippers in dual opposite direction. The compact multi-cusp H(-) ion source has been developed for the cyclotron. The 79.5 mm long ion source is 48 mm in diameter, which is consisting of a special shape filament, ten columns of permanent magnets providing a multi-cusp field, and a three-electrode extraction system. So far, the 3 mA∕25 keV H(-) beam with an emittance of 0.3 π mm mrad has been obtained from the ion source. The paper gives the design details and the beam test results. Further experimental study is under way and an extracted beam of 5 mA is expected.

Reliability test of an electron cyclotron resonance ion source for accelerator driven sub-critical system

The reliability test of an electron cyclotron resonance ion source developed for accelerator driven sub-critical system is carried out in China Institute of Atomic Energy. A unique technique to improve the reliability is adopted. The source is operated for more than 200 h at 75 keV, 100 mA extracted hydrogen current, while 2 beam trips are recorded in the period, and uninterrupted operation time is about 150 h. The experimental result is described.

AMS measurement of 32Si at the China Institute of Atomic Energy (CIAE)

A method for AMS measurement of 32Si has been established at CIAE with the HI-13 Tandem Accelerator and the newly developed ΔE-Q3D detection system. The production of 32Si, the preparation of a set of 32Si reference samples, and their subsequent analysis with the new system are described in detail. An overall suppression factor of more than 1012 for the interfering isobar 32S, resulting in a detection sensitivity below 32Si/Si=5×10−15, has been demonstrated for a limited set of artificially produced samples.

Realization and evaluation of doping and coating neutron sensitive MCP

High detection efficiency, good spatial resolution are both favorable properties in neutron detection of CPHS (Compact Pulsed Hadron Source) in Tsinghua University. Compact geometry (pore diameter of 13.5 μm and pitch of 16.25 μm) of micro-channel plate (MCP) may be beneficial for excellent resolution realization. However, MCP glass is not intrinsically neutron sensitive so neutron absorption nuclides should be introduced artificially. In this paper, thermal neutron sensitive MCPs are realized with 10mole% natB2O3 doping and ∼40 nm thick natGd2O3 coating layer on the inner surface of MCP pores respectively. Doping directly changes the component of MCP glass and coating is realized with atomic layer deposition (ALD) technique. Collimation experiments conducted with thermal neutron beam provided by a light water reactor of China Institute of Atomic Energy (CIAE) confirmed the neutron sensitivity of these two MCPs. Thermal neutron sensitive MCPs are realized and show potential to be used in high detection efficiency and spatial resolution thermal neutron imaging.