核动力工程

Study of Neutron Importance on Fast Neutron Burst Reactor

DU Jin-feng, YIN Yan-peng

2007, 28(S1): 1-3,7.

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The simulation calculation of neutron importance on fast neutron burst reactor （CFBR-II reactor） is introduced in this paper. The three-dimension model with complicated structure of CFBR-Ⅱ reactor is finished using MCNP program and the calculation of neutron value is realized by neutron multiplication method. In order to eliminate the difference of using the relative neutron importance in the hole of steel salver instead of the one in the core and reflector, the uniform sampling technique is applied to study the neutron importance detailed distribution along radial. The results indicate that the maximum neutron importance lies in areas of enrichment uranium or middle certain layer but not in system center or sphere core, the other areas are monotone descending along radial.

Calculation of CFBR-Ⅱ’s Prompt Neutron Decay Constant at Delayed Criticality by the Simulated Burst-Neutron Method

YIN Yan-peng, DU Jin-feng

2007, 28(S1): 4-7.

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By calculating foreign benchmark assemblies prompt neutron decay constants at delayed criticality, it is proved that the results calculated is faithful by using the simulated burst-neutron method. CFBR-Ⅱ’s prompt neutron decay constants are calculated with the method at five subcritical states. The prompt neutron decay constant attained at delayed criticality is 0.55μs^-1 by linear extrapolation.There are difference between calculational result and the experimental result. The article simply analyses reasons for the difference.

Probability Analysis for Event of Excess Pulse Fission Yield at CFBR-Ⅱ Reactor

LU Wei, FAN Xiao-qiang, LI Mao-hui

2007, 28(S1): 8-9,13.

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In this paper, structure, operation mechanism, and inherence security of CFBR-Ⅱ reactor were introduced, possible accident/event type were enumerated too. By using Probability Safety Analysis （PSA） method, event probability of excess pulse fission yield were obtained, and the importance analysis of bottom-events were performed, so as to give enough evidence for preventing accidents of pulse reactor and optimizing design of advanced pulse reactor.

Measurement of Prompt Neutron Decay Constant with Rossi-α on CFBR-Ⅱ Reactor

LIU Xiao-bo, FAN Xiao-qiang, JIANG Yong, YANG Cheng-de

2007, 28(S1): 10-13.

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Prompt neutron decay constant is the major characteristic parameter.Based on the Rossi-α theory and measurement technique, experiments were carried on measuring the prompt neutron decay constant with Rossi-α measurement equipment under the sub-critical and delayed critical of CFBR-Ⅱ reactor and a series of prompt neutron decay constant acquired provides the benchmark data for other experiments.

Study of Temperature Equilibrium Experiment on Critical Assembly with Plutonium

LI Mao-hui, FAN Xiao-qiang, YANG Cheng-de, QIU Dong, LU Wei

2007, 28(S1): 14-15,22.

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The inner and outer surface dynamic temperature monitoring in the core of critical assembly was performed with Ni10Cr-Cu45Ni thermocouple detectors. The temperature distribution was obtained in plutonium, stainless steel layer and polyethylene reflector through thermal conductivity differential equation during equilibrium temperature.It analyzed the temperature change effect on the system reactivity.

Influence of Neutron Spectrum to Prompt Neutron Decay Measurement

SONG Ling-li, ZHENG Chun

2007, 28(S1): 16-18.

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To evaluate the influence of leaking neutron spectrum and neutron flying time to the measurement of prompt neutron decay, prompt neutron decay curves at different locations inside and outside a polythene reflected plutonium metal sphere were calculated with MCNP-4C. Calculation results shows that the flying time difference for leaking neutrons with different energies distorts the curves by slowing down the decay and with the increase of the flying distance the distortion becomes more severe. When the flying time difference of the detected leaking neutrons is comparable to the time decay constant of the nuclear system, the time decay rate of leaking neutrons can not characterize the prompt neutron decay of the nuclear system.

Development and Verification of Pulse Time Sequence Acquisition Equipment

LIU Xiao-bo, FAN Xiao-qiang, YANG Cheng-de, JIANG Yong, LU Wei

2007, 28(S1): 19-22.

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This paper introduced the development and verification of the pulse time sequence acquisition （TSA） equipment, which achieved the 3 channel parallel input, 5ns timing precision, totalling 10⁹ counts pulse time sequence acquisition and storage based on the FPGA and DSP techniques, and realized the on-line, off-line Rossi-α analysis measurement. The equipment was applied for verification of the prompt neutron decay constant measurement and the results are consistent with the traditional Rossi-α measurement system.

Application of ²⁵²Cf Ionization Chamber in Nuclear Physics Parameter Measurements

ZHOU Hao-jun, SONG Ling-li, LI Jian-sheng, JIN Yu

2007, 28(S1): 23-26,52.

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The theory and the state of art of ²⁵²Cf ionization chamber as well as its applications in nuclear physics parameter measurements are described, which includes time-of-flight measurement, the scintillation detector neutron efficiency determination, prompt neutron decay constant measurement and ²⁵²Cf-sourcedriven noise analysis measurement.

Measurement of neutron Absorbed Dose of Samples in Tubes

DAI Shao-feng, ZHENG Chun, WANG Qiang

2007, 28(S1): 27-29.

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Based on the relation between absorbed dose and neutron flux, the absorbed dose of samples was measured in tubes by foil activation technique. The measurement shows that the neutron flux of material contained some hydrogen can be measured well using activition foils with reactivition threashold to determinate the neutron absorbed dose of samples.

Measurements on Burst Waveform and Parameter under Super-Prompt Critical of CFBR-Ⅱ Reactor

LIU Xiao-bo, FAN Xiao-qiang, JIANG Yong, YANG Cheng-de

2007, 28(S1): 30-34.

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Burst waveform measurement is the most important parameter measurement in burst pulse experimental research. In order to obtain pulse characteristic parameters which including super prompt activeity ρ₀ and peak power, etc, the real time measurement was carried out for the whole dynamic duration when CFBR-Ⅱ takes bursts The measurement system consists of six scintillation detector, 10B ionization chamber and high-speed parallel data acquisition equipment and gets the dynamic （from hundreds watt to 109 watt） waveform, and is used for practical application in many bursts and tested well for stable performance and credibility.

Characteristic Investigation of the Long Counters and Application in Measuring Shield Capability

LI Jun-jie, ZHENG Chun, QIU Dong, DAI Shao-feng

2007, 28(S1): 35-36,59.

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The long counter’s Supply Voltage is 1450V that confirmed by ²⁵²Cf neutron source, The effective center is 13.5cm away from the front surface of the long counter. It found that the long counter is smooth characteristic by comparing count rate with different thickness polyethylene that moderating the same neutron source. attenuation coefficient of a new developed boronizing polyethylene is measured using the BF₃ long counters, and the experimental result is 0.236, the calculated value with MC is 0.218. both accord with range of error.

Measurement of Pulse Neutron Flux in CFBR-Ⅱ

LI Jian-sheng, WANG Qiang, ZHENG Chun, GAO Ren-zhen, WU Jian-hua

2007, 28(S1): 37-39.

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To measure the pulse neutron flux in CFBRⅡ, neutron spectrum have to be considered and corrected in different region. Using ²³⁹Pu ionization chamber and Sulphur activation foil, 28 places are calibrated. 5% fractional uncertainty is introduced in the flux measurement. As yield is 1.10×10¹⁶ fissions, pulse neutron flux is 5.87×10¹³ cm^-2 at the point which is 50mm distance from the bottom of radiation chamber, the combined standard uncertainty is 11%.

Multi-Output Method of Ionization Chamber

ZHOU Hao-jun, LI Jian-sheng, ZHENG Chun, JIN Yu

2007, 28(S1): 40-42.

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An introduction was given about multi-output method of ionization chamber （or fission chamber）. This method reduced response time and mitigated α-particles signal Pile-up that induced by much fissionable materials, It enable the ionization chamber containing more nuclear materials and improving the detection efficiency.

Neutron Importance Measurement in Center Hole Cross Bare ²³⁹Pu Shells

DAI Shao-feng, ZHENG Chun, LI Jun-jie, YIN Yan-peng

2007, 28(S1): 43-44,55.

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The Neutron importance in the hole cross bare ²³⁹Pu shell was measured using long counter and gained the neutron importance distribution. The distribution configuration is well consistent with calculation results. The data shows that the distribution is M type, the maximum value is 1.02 times of the center, and the value on the surface is about 65% of the center.

Applications of the Slab Type Mini ²⁵²Cf Source on the Nuclear Physics Experiment

JIN Yu, LI Jian-sheng, ZHOU Hao-jun, SONG Ling-li, ZHANG Yi

2007, 28(S1): 45-48.

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This paper briefly described the application of the slab type mini ²⁵²Cf source in nuclear physics, nuclear hardening and Nuclear pumped Laser experiment. It emphasized on the design features of ²⁵²Cf Vaccam chamber in experiment device and some kinds of experiment testing system

The Design of Password Authorization System on Reactor Based on NiosⅡ

LI Meng, LU Yi, RONG Ru

2007, 28(S1): 49-52.

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The design of embedded password authorization system of reactor based on NiosⅡCPU is introduced here. This design uses the SOPC technology based on the Cyclone series FPGA as a digital bench to integrate microprocessor、timers、RS-232, PS/2,LCD,Flash, SDRAM,etc into a FPGA chip. The system has functions that it can be set work status, its password can be modified and storage via keyboard or computer, and its LCD can display information during working. It is proved that the system achieves design goals in primary experimentation.

Fast Response Safety Instrument of Fast Neutron Burst Reactor

HAN Hui-lin, LI Meng, ZHENG Chun, ZHANG Yi

2007, 28(S1): 53-55.

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To ensure the fast neutron burst reactor being sub-critical state immediately after fission burst, a fast response safety instrument is developed. The instrument consists of scintillation detector, photomultiplier, preamplifier, amplifier and trigger. The trigger signal can be produced in 12μs after the preset threshold value is exceed, and then trigger the safety block to drop 5mm in 100ms. The instrument was applied at CFBR-II reactor, and has given out scram signal in time more than 200 times burst operation. The fast response safety instrument triggers safety block to drop 5mm less than 90ms to ensure the safety of reactor.

Developing of Small Precision Gearing System for Zero-Power Reactor’s Reactivity Control

YE Cen-ming, JIANG Zhi-guo, ZHANG Hai-bin, ZHANG Yi, RONG Ru

2007, 28(S1): 56-59.

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We developed the system of the small precision gearing that makes up of linear actuator, rotating transformer, angle display, control system and drive circuit .We did a performance test of the system in the laboratory. The result indicated that the performance met zero-power reactor’s reactivity control requirement.

Research of Period Measuring Instruments on CFBR-Ⅱ Reactor Based on DSP

BAI Zhong-xiong

2007, 28(S1): 60-63.

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For the Period measuring system of CFBR-II Reactor, DSP has been introduced as a new digital technique. The TMS320F2812 DSP chip is adopted as the core controller to realize Period measuring of CFBR-II Reactor. In this paper, the successful program of DSP measurement system is introduced in both hardware and software technology in detail.

Startup-Time Measuring Instrument for Burst Reactor

ZHANG Yi, FAN Xiao-qiang, HU Jin-quan

2007, 28(S1): 64-66.

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The startup-time measuring instrument for fast burst reactor utilizes the photoelectric sensor to get the time points when the control rod leaves the outer end and reaches the inner end. The power of fast burst reactor is measured by the scintillation probe. Intersil ICM7226B chip is used to realize function of counter and display driver. The instrument has 5 ranges of time surveying with 8-digit LED display. The instrument has been applied in experiments, the measurement results fulfil the needs of concerned physical experiments.

Design of Reactivity Adding Speed Measurement System on Critical Assembly

XIANG Wei-ling, YE Cen-ming, JIANG Zhi-guo, FAN Xiao-qiang, HUANG Yi-chao

2007, 28(S1): 67-70.

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This paper introduced the components, working principle and software design of reactivity adding speed measurement system. The system is used in the Critical assembly burst experiments for pulse rod injection speed measurement. Practical result shows that the performance and operation of the system are reliable

2007 Vol. 28, No. S1