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通过用阈探测器测量热中子引起的~(235)U裂变中子能谱,研究了SAND-Ⅱ和RDMM方法的解谱能力。并用蒙特卡罗误差分析程序分析了两种解谱方法的输入数据误差。对SAND-Ⅱ方法中解的唯一性误差和RDMM方法中权重函数的影响进行了讨论。两种方法对未知谱中结构的灵敏程度也作了简单的检验。结果表明,SAND-Ⅱ和RDMM是解快中子光滑变化能谱的较好方法。当未知谱中有简单结构时,用SAND-Ⅱ方法更为合适。 相似文献
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核动力堆安全壳内外中子能谱和剂量测量 总被引:1,自引:1,他引:1
利用自制的多球谱仪测量了某核动力反应堆安全壳内外的中子能谱和剂量当量率。对安全壳外测量,中心探测器为球形^3He正比计数管;对安全壳内测量,中心探测器为球形金箔。系统的响应函数用MCNP程序计算,解谱程序为MIEKEB。为验证系统响应函数计算的准确性,进行了一些实验测量,并与理论计算结果进行了比较。结果表明,测量结果与计算结果在不确定度范围内相吻合。 相似文献
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通过用阈探测器测量热中子引起的~(235)U裂变中子能谱,研究了SAND-Ⅱ和RDMM方法的解谱能力。并用蒙特卡罗误差分析程序分析了两种解谱方法的输入数据误差。对SAND—Ⅱ方法中解的唯一性误差和RDMM方法中权重函数的影响进行了讨论。两种方法对未知谱中结构的灵敏程度也作了简单的检验。结果表明,SAND-Ⅱ和RDMM是解快中子光滑变化能谱的较好方法。当未知谱中有简单结构时,用SAND—Ⅱ方法更为合适。 相似文献
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本文介绍了一种为远洋现场调查而研制的低本底β计数-α能谱测量装置。该测量装置能同时进行低活度的β测量和α能谱分析,克服了用两套仪器分别测量β计数和α能谱的麻烦,并减小了测量误差。 相似文献
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不同成分中子参考辐射场是对中子防护材料性能测试的基本条件。为获得较理想的测试中子防护材料的中子参考辐射场,构建基于3He正比计数管的多球中子能谱测量系统,对基于241Am-Be和252Cf中子源的中子辐射场慢化情况进行MCNP模拟和能谱实验测量。为准确判断实验室校准参考位置的中子散射情况,基于多球中子能谱测量系统,开展了中子散射成分测量。采用ICRP推荐的注量-剂量转换系数对能谱进行了剂量率转化,与使用长计数器的测量结果进行比较,发现在校准参考位置的剂量率相对偏差≤20%。开展了聚乙烯慢化同位素中子源获得特定能谱的实验研究,进行了慢化谱的模拟计算和实验测量,两者结果符合较好。该工作为后续的中子计量测试和中子防护材料测试提供了可用的中子参考辐射场。 相似文献
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为了更加有效地扣除中子活化能谱散射本底,提高中子活化能谱分析的准确度,利用傅里叶变换本底扣除法,对MCNP程序包模拟14 Me V脉冲中子照射煤样获取的活化γ能谱进行了本底扣除。通过对全能峰面积解析误差的分析,表明该方法可有效提高特征峰面积的解析准确度。 相似文献
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《中国原子能科学研究院年报(英文版)》2016,(0)
正Researches,such as measurement of doublebeta decay in nuclear physics,neutrino measurement in particle physics and dark matter directmeasurement in new physics,which need critical environments which radioactive background should be extremely low can be called ultra-low 相似文献
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在核电厂反应堆的反应性测量中,γ本底电流、中子源引入的电流、电路噪声等干扰项在实测电流中占有显著份额,给反应性的测量计算带来很大影响,在动态刻棒等反应性测量工作中必须对其进行修正。本文分析了本底与中子源电流对反应性测量的影响,并自主开发了一种本底电流、中子源电流修正方法--双重拟合法。该方法基于点堆模型,通过对包含本底与中子源的逆动态方程的分析,计算得到准确的反应性以及本底电流、中子源电流。通过试验堆动态刻棒实验的数据对本方法进行了验证,得到了理想的结果。 相似文献
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《Journal of Nuclear Science and Technology》2013,50(10):764-776
A new form of 6Li sandwich counter has been developed for use in measurements of neutron spectra in fast critical assemblies. The counters have two large surface area diodes approached very close to each other, on one of which is evaporated the target 6Li. This arrangement proves to provide a ten-fold increase of detection efficiency, while the resolution is improved by approximately ½ compared with currently used counters. The new counters were first tested on mono-energetic neutrons, after which neutron spectrum measurements were performed on natural uranium blocks, in the fast source reactor “YAYOI”, in the FCA IV-l-P and in the FCA V-3 core. The resulting spectra are compared with the measurements made with other types of counter and with calculated data. Proof was obtained that the new counter can serve practically and usefully for in-core measurements of fast neutron energy spectrum between 0.8 and 5 MeV. 相似文献
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《Journal of Nuclear Science and Technology》2013,50(7):601-616
We have performed the measurement of neutron emission spectra from 238U using a time-of-flight technique, and deduced the following data; (1) the prompt fission neutron spectra for 2 MeV incident neutrons at two emission angles of 90° and 135°, (2) the double-differential neutron emission cross sections at the incident energies of 1.2, 2.0, 4.2, 6.1 and 14.1 MeV. The emission spectra and the cross sections for scattering process were also deduced by subtracting the fission neutrons from the experimental spectra. The experimental results were compared with other experiments and the evaluations of JENDL-3 and ENDF/B-IV. From the fission spectrum data ranging from 2 to 12 MeV, we have derived the best fit parameters for the Maxwellian and Watt type distribution functions. The experimental spectra are described with the Maxwellian spectrum with temperature of 1.24–1.26 MeV and are softer than both evaluations. The spectra and cross sections for inelastic-scattering showed substantial disagreement with the evaluations concerning the discrete levels between 0.5 and 1.2 MeV, and continuum neutrons due to evaporation and pre-equilibrium processes. The secondary neutron angular distributions at 14 MeV incident energy were reproduced fairly well with the systematics. 相似文献
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《Journal of Nuclear Science and Technology》2013,50(9):708-722
For the assessment of neutron cross section data for fluorine, angular neutron spectra in the lithium fluoride (LiF) and polytetrafluoroethylene ((CF2)n) piles were measured in the energy range from a few keV to a few MeV by the time-of-flight method with an electron linac, and the results were compared with those calculated by using nuclear data from JENDL-2 and ENDF/B-IV. Spatial distributions of neutron and X-ray fluxes were also measured in the test piles by the activation method, and the influence of photoneutrons generated in the sample material on the neutron spectrum in each pile was estimated. As a result, it was found that their influence on the neutron spectrum shape below 1 MeV was not so large as was necessary to be taken into account for the present assessment. The calculated spectra using the JENDL-2 data and the ENDF/B-IV data show generally good agreement with those measured in both piles. However, both calculations underestimate the neutron fluxes around several 100 keV, and overestimate those below 100 keV, when they are normalized in the energy range of 10 keV~1 MeV. Large discrepancies are found between the shapes of the measured and calculated spectra around the resonances of fluorine cross section below 100 keV. The present measurements and analyses suggest that the reevaluations of the inelastic and elastic scattering cross sections below 1MeV and the resonance cross sections below 100 keV are necessary to reduce the observed discrepancies. 相似文献