240Am半衰期的测量

²⁴⁰Am的半衰期对准确测量²⁴¹Am(n,2n)²⁴⁰Am反应截面具有重要作用，当前评价的数据50.8(3) h是对²⁴⁰Am的987.8 keV γ射线用Ge(Li)探测器跟踪测量6 d的结果，测量时间不到3个半衰期，使得测量结果的不确定度偏大。本文利用Geant4模拟软件建立了阱型HPGe探测器的测量模型，模拟计算了不同Pb吸收厚度下²⁴⁰Am高能γ射线的探测效率，确定使用阱型HPGe探测器配合吸收X射线和低能γ射线的Pb吸收体可有效提高²⁴⁰Am高能γ射线的探测效率。根据Geant4模拟计算的结果，Pb吸收体厚度为1 mm时，对²⁴⁰Am的888.8 keV和987.8 keV两条特征γ射线的探测效率分别为14.1%和13.3%。在中国原子能科学研究院的HI-13串列加速器上通过²⁴²Pu(p,3n)反应生产了²⁴⁰Am，制备了约700 Bq的²⁴⁰Am测量源，用上述方法跟踪测量²⁴⁰Am的888.8 keV和987.8 keV两条特征γ射线的强度，时间超过18 d，用最小二乘法拟合得到其半衰期为50.79(5) h，结果与评价结果一致，但减小了不确定度。     

井型电离室的研制

本文阐述的DLS-206型井型电离室可用于测量放射性同位素活度。它配合动电容静电计和数字电压表进行测量,其稳定性好于0.1％。该电离室可以用于测量β,γ源。γ能量响应>25keV。对~(125)I,~(241)Am,~(51)Cr,~(137)Cs,~(60)Co的γ灵敏度依次是1.6×10~(-13),1.3×10~(-13)0.3×10~(-13),3.1×10~(-13),7.0×10~(-13)A/μCi;对~(32)P的β灵敏度是0.3×10~(-13)A/μCi。     

γ谱仪测量土壤样品探测效率模拟刻度研究

针对Ф75mm×25mm的土壤样品,利用HPGeγ谱仪,分别用241Am、137Cs、~(60)Co混合点源测量5种高度的样品剖面上不同位置的全能峰效率,确定点源全能峰效率随半径变化的函数关系,对该函数进行数值积分计算可以得到59.54keV、661.66keV、1173.2keV和1332.5keVγ射线的面源全能峰效率,进一步拟合确定面源全能峰效率随样品高度变化的函数参数,对样品高度进行数值积分计算得到Ф75mm×25mm样品的体源全能峰效率。结果表明,点源模拟计算的体源全能峰效率和标准体源全能峰效率进行比较,两者在10%以内符合。因此,在没有标准体源的情况下,用已知活度的标准点源模拟体源进行全能峰效率刻度的方法替代标准体源进行效率刻度方法是可行的。     

气体裂变产物88Kr半衰期测量

为准确测定气体裂变产物⁸⁸Kr的半衰期，本工作从辐照铀靶中分离得到3个放化纯的⁸⁸Kr气体测量源。以⁸⁵Kr作内标监督源，¹³⁷Cs或⁵⁷Co作外标监督源，使用多个HPGe探测器分别采用单探测器位置接力法和双探测器位置接力法跟踪测量⁸⁸Kr 196.3 keV能量的特征γ射线，跟踪时间均在8个半衰期以上，以获得其半衰期数据。对3次独立测量数据用多种方法进行处理，最终得到⁸⁸Kr半衰期测定结果为（2.796±0.015） h。     

Ca无中微子双β衰变的实验研究

报道了国内首次开展双β衰变实验的情况。实验使用特大体积天然CaF_2晶体同时作为双衰变源和电子探测器。实验在北京西郊门头沟煤矿矿井中进行。实验测量的~(48)Ca无中微子双β衰变的寿命下限为3.6×10~(21)a。根据庆承瑞,何祚庥,吴慧芳的理论半衰期,计算有效中微子质量上限(m)小于13.7eV,右手流混合参量(η )≤1.17×10~(-5)。目前实验正在进行,以期实验的寿命下限过到10~(22)a。     

微量硼的热中子瞬发γ射线分析方法

反应堆热中子束流引起地质样品中硼的~(10)B(n,αγ)~7Li反应,用HPGe探测器测量其反应的478 keV瞬发γ射线峰面积,与标准样品比对,得到30个地质样品中硼的含量为8×10~(-6)～160×10~(-6),相对误差为16%～5%。     

~(48)Ca无中微子双β衰变的实验研究(英文)

本文报道了国内首次开展双β衰变实验的情况。实验使用特大体积天然CaF_2晶体同时作为双衰变源和电子探测器。实验在北京西郊门头沟煤矿矿井中进行。实验测量的~(48)Ca无中微子双β衰变的寿命下限为3.6×10~(21)a。根据庆承瑞,何祚庥,吴慧芳的理论半衰期,计算有效中微子质量上限〈m〉小于13.7eV,右手流混合参量〈η〉≤1.17×10~(-5)。 目前实验正在进行,以期实验的寿命下限达到10~(22)a。     

~(176)Hf(n,2n)~(175)Hf反应截面测量

采用相对测量技术,以活化法对13.4～14.8MeV范围内的176Hf(n,2n)175Hf反应截面进行了测量。样品固定在距离D-T中子源20cm处的圆环的不同位置上进行中子辐照,采用93Nb(n,2n)92Nbm作为监测反应,活化产物采用高纯锗探测器进行了测量,所得14MeV附近的176Hf(n,2n)175Hf反应截面实验值为(2100±85)mb,对实验结果与公开文献值和ENDF/B6.8评价库数据进行了比对。     

常用辐射防护剂量监测仪表能量特性研究

通过采用X参考辐射和防护水平(~(137)Cs源、~(60)Co源)γ参考辐射,对目前常用辐射防护监测剂量仪表的能量响应特性开展实验研究,其光子能量范围为33keV~250keV、662keV和1250keV。文章主要介绍实验用辐射源及参考辐射场测量方法、剂量仪表校准及能量响应测量方法。实验得出常用的GM计数管、电离室和闪烁体三类场所剂量仪表能量响应曲线,并对测量数据进行处理分析,从而得到这三类剂量仪表的能量响应剂量特性。     

D-D反应分支比和截面与入射氘核能量的关系

本文根据已发表的实验资料,提出了描述D(d,n)~3He和D(d,p)T反应分支比及全截面的经验公式。氘核能量在10～1.4×10~4keV之间,经验公式与实验结果之间得到了满意的符合。     

Nuclear Data Sheets for A = 175

The 1965 version of Nuclear Data Sheets for A = 175 has been revised on the basis of experimental data received prior to April 1975. Experimental data, arguments for J^π-assignments, and detailed level schemes are presented. A large amount of new information is given for the ¹⁷⁵Yb, ¹⁷⁵Lu, and ¹⁷⁵Hf level schemes. Very little is known about the decays of ¹⁷⁵W and the more neutron-deficient isobars in this A-chain. Unless stated otherwise, all energies in this compilation are given in keV.     

Blistering of niobium due to 0.5 to 9 keV helium and hydrogen bombardment

Blistering of well-annealed niobium single crystals due to 0.5 to 9 keV helium and hydrogen ion bombardment at temperatures between ?110°C and 1000°C has been investigated by Rutherford backscattering (RIBS) in double alignment and with a scanning electron microscope (SEM). For He bombardment blistering was observed by RIBS in the temperature range investigated for all energies above 1 keV. The critical dose at which blisters first appear is about 1 to 2 × 10¹⁷ incident He ions per cm². It increases slightly with increasing ion energy and with decreasing target temperature. Blisters of 500 to 5000 Å in diameter were found. The depth at which the blisters develop increases from ≈ 180 Å for 1 keV to 1100 Å for 9 keV He ions. It is a factor of ≈ 3 larger than the theoretical mean range of the ions in amorphous material. Above ≈ 600°C grain boundaries develop extending also into the unbombarded region. For hydrogen bombardment no blistering could be observed at room temperature up to doses of 2 × 10¹⁹ ions per cm².     

Electrical Properties of Uranium Carbonitride

Rapid separation using NTA in paper electromigration was applied to the study of the γ-decay of ¹⁴⁸Pr and ¹⁴⁹Pr produced in the fission of ²³⁵U. The γ-ray spectrum was measured with a high-resolution Ge(Li) detector. The γ-transitions found to decay with half-lives shorter than 3 min were: 135, 162, 256, 300, 511, 614, 696, 868, 1,022 and 1,248 keV. Of these, the values of 300 keV, and of 135 and 162 keV were in fair agreement with those reported for ¹⁴⁸Pr and ¹⁴⁹Pr. The decay plot of the strong photopeak of 300 keV presented good linearity and the accurate half-life of ¹⁴⁸Pr could be determined as 2.30±0.03 min, which is longer than the 1.98 min reported for ¹⁴⁸Pr. Similar decay plots of both photopeaks at 135 and 162 keV gave a half-life of 2.9±0.1 min for ¹⁴⁹Pr, which again is longer than the reported value of 2.3 min. Other low intensity photopeaks at 256, 696, 868 and 1,022 keV decaying with half-lives of 2.1～2.4 min can possibly be attributed to ¹⁴⁸Pr. The γ-transitions of 110, 578 and 742 keV reported for ¹⁴⁹Pr could not be observed in this experiment.     

Graphite surface erosion by 100 keV helium and hydrogen bombardment

Surface erosion in pyrolytic graphite by 100 keV ⁴He⁺ and 200 keV H⁺₂ ion bombardment has been observed by scanning electron microscopy. The particle fluence ranged from 1 × 10¹⁷ to 5 × 10¹⁸ particles/cm². Although the surface is eroded at 1 × 10¹⁷ particles/cm² in helium bombardment, it is not eroded so heavily even at 5 × 10¹⁷ particles/cm² in hydrogen bombardment. In helium bombardment flaking is significantly observed at 1 × 10¹⁸ particles/cm², and a cone structure appears at 5 × 10¹⁸ particles/cm², which is produced after the first cover flakes off completely. In hydrogen bombardment at 1 × 10¹⁸ particles/cm², many circular blisters are formed which are sputtered off at 5 × 10¹⁸ particles/cm². The surface roughness of the target also affects the erosion.     

SiPM耦合LYSO晶体探测器的能量分辨和时间分辨

本文采用符合测量的方法研究了SENLE公司生产的型号为Micro FC-30035-SMT的Si PM光电转换器件耦合尺寸为3×3×10 mm的LYSO晶体组成的闪烁探测器的能量分辨率和时间分辨。该探测器测得22Na放射源能量为511 ke V光子的能量分辨率(FWHM)为16%,时间分辨达135 ps。     

Preliminary Results of IS Plasma Focus as a Breeder of Short-Lived Radioisotopes 12C(d,n)13N

Modified IS (Iranian Sun) plasma focus (10 kJ,15 kV, 94 ??F, 0.1 Hz) has been used to produce the short-lived radioisotope ¹³N (half-life of 9.97 min) through ¹²C(d,n)¹³N nuclear reaction. The filling gas was 1.5?C3 torr of hydrogen (60%) deuterium (40%) mixture. The target was solid nuclear grade graphite with 5 mm thick, 9 cm width and 13 in length. The activations of the exogenous target on average of 20 shots (only one-third acceptable) through 10?C13 kV produced the 511 keV gamma rays. Another peak found at the 570 keV gamma of which both was measured by a NaI portable gamma spectrometer calibrated by a ¹³⁷Cs 0.25 ??Ci sealed reference source with its single line at 661.65 keV and ²²Na 0.1 ??Ci at 511 keV. To measure the gamma rays, the graphite target converts to three different phases; solid graphite, powder graphite, and powder graphite in water solution. The later phase approximately has a doubled activity with respect to the solid graphite target up to 0.5 ??Ci of 511 keV and 1.1 ??Ci of 570 keV gamma lines were produced. This increment in activity was perhaps due to structural transformation of graphite powder to nano-particles characteristic in liquid water.     

Method for Determining Degassing Constant of Xenon in Liquid Sodium

A method for determining the xenon degassing constant from liquid sodium to the cover gas by measuring the ¹³⁵Xe and ^135mXe release rate ratios, which were produced by the decay of ¹³⁵I in liquid sodium, was investigated using the Toshiba inpile fission product loop. Release rate ratios of ¹³⁵Xe to ^135mXe showed values of 9.9~7.6 at a sodium temperature range of 240~390°C and degassing constant of 1.2 × 10^?3-2.6 × 10^?3 sec^?1, which correspond to degassing half-life of 9.7~4.4 min, were obtained. This method is found to be effective for the determination of fission gas degassing constant, which has a corresponding half-life between several minutes to 40 min and will be useful for the study of fission gas transport phenomena in liquid sodium systems.     

Estimation of Exposure from 147Pm-Activated Self-Luminous Plate

The majority of radioactive self-luminous paint produced in Japan uses ¹⁴⁷Pm.

The characteristics of the radiation from a ¹⁴⁷Pm-activated self-luminous plate which had a luminous area of 12×8 cm² and radioactivity of 12.5 mCi were examined. Bremsstrahlung was produced from the luminous plate absorbing the 220 keV β-particles of ¹⁴⁷Pm. The energy of the bremsstrahlung was analyzed with use of both NaI scintillation and Ge solid state detectors: the spectrum obtained showed a peak at around 50 keV and also a small peak due to γ-rays emitted from the ¹⁴⁷Pm at 121 keV. Measurements of the bremsstrahlung made with Lauritsen electroscope, film badges, fluoroglass dosimeters and thermoluminescent dosimeters gave estimated exposure rates of at most only 0.5 and 0.3 mR/hr respectively at distances from the plate of 3 and 7 cm.     

半导体器件在辐射作用下的电学输出性能研究

半导体结型器件是决定辐射伏特效应同位素电池能量转换效率的核心部件。采用加速器产生的不同能量电子束和63Ni源的β射线对硅基PIN结型器件进行辐照,在线测量了其电学输出性能。当电子束能量为18 keV,可得到大于4%的能量转换效率;电子束能量为6 keV,能量转换效率在0.16%～0.33%之间; 活度2.96×108 Bq的63Ni源片辐照的能量转换效率为0.1%左右。