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Measurement of neutron flux at the Initial Phase of Discharge in EAST

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Plasma Science and Technology 2011年第2期13卷 162-166页

作者：钟国强胡立群李晓玲林士耀周瑞杰 Institute of plasma physics Chinese academy of sciences

neutron emission in EAST was investigated by a time-resolved monitor system which consists of four 3He proportional counters and a 235U fission chamber. The D-D neutron flux increased approximately an order of magnitude during the 27 MHz ion-cyclotron radio frequency （ICRF） heating, demonstrating that the ICRF wave heated the plasma effectively. In addition in lower hybrid wave （LHW） experiment with higher plasma parameters D-D neutrons were also detected. However, masses of photoneutrons were generated in Ohmic discharges with low plasma density. Effect of plasma density on the production of photoneutrons was studied, and it is found that LHW can suppress the generation of the runaway electrons and reduce the share of the photoneutrons effectively.

关键词： neutron flux plasma diagnostic EAST tokamak

Monitoring method for neutron flux for a spallation target in an accelerator driven sub-critical system

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Chinese Physics C 2016年第7期40卷 129-135页

作者：赵强贺智勇杨磊张雪荧崔文娟陈志强徐瑚珊 Institute of Modern Physics Chinese Academy of Sciences Lanzhou 730000 China University of Chinese Academy of Sciences Beijing 100049 China

In this paper, we study a monitoring method for neutron flux for the spaUation target used in an accelerator driven sub-critical （ADS） system, where a spallation target located vertically at the centre of a sub-critical core is bombarded vertically by high-energy protons from an accelerator. First, by considering the characteristics in the spatial variation of neutron flux from the spallation target, we propose a multi-point measurement technique, i.e. the spallation neutron flux should be measured at multiple vertical locations. To explain why the flux should be measured at multiple locations, we have studied neutron production from a tungsten target bombarded by a 250 MeV-proton beam with Geant4-based Monte Carlo simulations. The simulation results indicate that the neutron flux at the central location is up to three orders of magnitude higher than the flux at lower locations. Secondly, we have developed an effective technique in order to measure the spallation neutron flux with a fission chamber （FC）, by establishing the relation between the fission rate measured by FC and the spallation neutron flux. Since this relation is linear for a FC, a constant calibration factor is used to derive the neutron flux from the measured fission rate. This calibration factor can be extracted from the energy spectra of spallation neutrons. Finally, we have evaluated the proposed calibration method for a FC in the environment of an ADS system. The results indicate that the proposed method functions very well.

关键词： accelerator driven sub-critical (ADS) system neutron flux spallation target fission chamber fissioncross section

Influence of thermal and resonance neutron on fast neutron flux measurement by ^(239)Pu fission chamber

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Chinese Physics C 2015年第1期39卷 50-53页

作者：曾丽娜王强宋凌莉郑春 Institute of Nuclear Physics and Chemistry China Academy of Engineering Physics Key Laboratory of neutron Physics China Academy of Engineering Physics

The ^239Pu fission chambers are widely used to measure fission spectrum neutron flux due to a fiat response to fast neutrons. However, in the meantime the resonance and thermal neutrons can cause a significant influence on the measurement if they are moderated, which could be eliminated by using ^10B and Cd covers. At a column enriched uranium fast neutron critical assembly, the fission reaction rates of ^239gpu are measured as 1.791 × 10^-16 2.350 × 10^-16 and 1.385×10^-15 per second for 15 mm thick ^10B cover, 0.5 mm thick Cd cover, and no cover respectively, while the fission reaction rate of 239pu is rapidly increased to 2.569×10^-14 for a 20 mm thick polythene covering fission chamber. The average 239pu fission cross-section of thermal and resonance neutrons is calculated to be 500 b and 24.95 b with the assumption of 1/v and 1/E spectra respectively, then thermal, resonance and fast neutron flux are achieved to be 2.30×10^6, 2.24×10^6 and 1.04×10^8 cm^-2·s^-1.

关键词： fission chamber neutron flux thermal and resonance neutrons fast neutrons

Reconstruction of the neutron flux in a Slab Reactor

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World Journal of Nuclear Science and Technology 2012年第4期2卷 181-186页

作者： Adilson Costa da Silva Aquilino Senra Martinez Alessandro da Cruz Goncalves Nuclear Engineering Department Federal University of Rio de JaneiroRio de JaneiroBrazil

In this electronic article we use the one-dimensional multigroup neutron diffusion equation to reconstruct the neutron flux in a slab reactor from the nuclear parameters of the reactor, boundary and symmetry condition, initial flux and?keff. The diffusion equation was solved analytically for one single homogeneous fuel region and for two regions considering fuel and reflector. To validate the method proposed, the results obtained in this article were compared using reference methods found in the literature.

关键词： neutron Diffusion Equation neutron flux Slab Reactor

neutron yield measurement system of HL-2A tokamak

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Plasma Science and Technology 2022年第6期24卷 38-44页

作者： Guoliang YUAN Zuowei WEN Lingfeng WEI Jinwen ZHANG Qingwei YANG Southwestern Institute of Physics Chengdu 610225People's Republic of China

This research presents the development of HL-2A neutron yield measurement which includes^(235)U fission chamber and BF_(3)and^(3)He proportional *** noise formula of the radiation detection signal amplification system was derived to guide the development of the signal amplification *** all detectors were calibrated in situ by using the^(252)C_(f)neutron *** neutron yield of the HL-2A during neutral beam heating was *** results indicate that the developed neutron flux diagnostic system can obtain neutron yield results under various experimental conditions of the HL-2A tokamak,and can provide information on neutron yield.

关键词： HL-2A neutron yield neutron flux fission chamber in situ calibration equivalent noise charge

Conceptual design and safety characteristics of a new multi-mission high flux research reactor

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Nuclear Science and Techniques 2023年第3期34卷 9-24页

作者： Wei Xu Jian Li Heng Xie Zhi-Hong Liu Jing Zhao Fei Xie Lei Shi School of Nuclear Science and Engineering Beijing Key Laboratory of Passive Safety Technology for Nuclear EnergyNorth China Electric Power UniversityBeijing 102206China Institute of Nuclear and New Energy Technology Collaborative Innovation Center of Advanced Nuclear Energy TechnologyKey Laboratory of Advanced Reactor Engineering and Safety of Ministry of EducationTsinghua UniversityBeijing 100084China

Research reactors with neutron fluxes higher than 10^(14) n cm^(−2) s^(−1) are widely used in nuclear fuel and material irradiation,neutron-based scientific research,and medical and industrial isotope *** high flux research reactors are not only important scientific research facilities for the development of nuclear energy but also represent the national comprehensive technical *** has several high flux research reactors that do not satisfy the requirements of nuclear energy development.A high flux research reactor has the following features:a compact core arrangement,high power density,plate-type fuel elements,a short refueling cycle,and high coolant velocity in the *** characteristics make it difficult to simultaneously realize high neutron flux and optimal safety margin.A new multi-mission high flux research reactor was designed by the Institute of Nuclear and New Energy Technology at Tsinghua University in China;the reactor can simul-taneously realize an average neutron flux higher than 2.0×10^(15) n cm^(−2) s^(−1) and fulfill the current safety *** high flux research reactor features advanced design concepts and has sufficient safety margins according to the preliminary safety *** on the analysis of the station blackout accident,loss of coolant accident,and reactivity accident of a single-control drum rotating out accidently,the maximum temperature of the cladding surface,minimum departure from nucleate boiling ratio,and temperature difference to the onset of nucleate boiling temperature satisfy the design limits.

关键词： High flux research reactor neutron flux Safety analysis Maximum temperature of cladding surface Departure from nucleate boiling ratio

Study of neutron radiation effect in La Br_3 scintillator

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Chinese Physics C 2015年第10期39卷 92-95页

作者：卢毅宋朝晖李刚谭新建赵晓川张侃 Northwest Institution of Nuclear Technology

The resistance to neutron irradiation of LaBr3 scintillator was studied in this work. The change of background counting rate, light output and energy resolution of the LaBra scintillator were analyzed to determine whether the scintillator was damaged under different neutron flux rates induced by 24：Am-Be, D-T neutron generator, and reactor neutron source. The results show that the neutron radiation damage in LaBr3 scintillator is mainly affected by neutron flux rate. Under low flux rate, the properties of the scintillator were hardly changing, while under high flux rate, there is obvious deterioration in the background spectra and in the energy resolution because of the neutron activation. After a period, the neutron radiation damage will spontaneously recover.

关键词： neutron resistance LaBr3 scintillator neutron flux

Ontology of Quantum Gravity

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Journal of Modern Physics 2023年第11期14卷 1392-1408页

作者： Edwin Eugene Klingman Cybernetic Micro Systems Inc. San Gregorio CA USA

A theory of Quantum Gravity based on Primordial Field Theory is applied to a fundamental particle, the neutron. The result is compared to the current quantum description of the neutron bouncing in a gravitational field. Our quantum gravity theory yields results in agreement with the Q-bounce experimental data, but ontologically different from quantum mechanics. The differences are summarized and imply that this experiment on a fundamental particle has the potential to radically alter the ontology of field theory.

关键词： Loop Quantum Gravity Ontology neutron Bounce Primordial Field Theory Q-Bounce neutron flux