Study of the Structure of Borromean Nucleus 17Ne

In the present research, we used the 17Ne beam at 30.8 MeV/u to bombard the 43mg/cm2 12C target and measured the angular correlations between the fragments and emitted proton. In the break-up reaction of 17Ne, one-proton knockout would result in an unstable nu-cleus 16F, which would further decay by the proton emission. The measured angular correlation between the 16F momentum and the relative momentum of its decay products was compared with theoretical calculations and indicated that the valence proton in 17Ne has the most probability to be situated in the s1/2 orbital with a small admixture of the d5/2 orbital. The present results suggest that 17Ne has a halo structure.     

Study of Isotopic Distribution of the Projectile-like Fragments Produced in the 17,18N + 197Au Reactions at 33 MeV/u

The experimental data of the isotopic distribution for projectile-like fragments are presented for the 17,18N + 197Au reaction at 33MeV/u. The width of the isotopic distributions for 18N projectile is significantly broader than that for 17N projectile, and the average N/Z ratio of the former shifts to higher neutron number side. As long as the realistic nucleon density distribution is used, the isotopic distribution for fragments is reproduced by the simple abrasion-ablation model calculation, which thus provides an independent way to determine the surface distribution of the nuclear matter density for neutron-rich nuclei.     

Study on Fragments Emission in the 64Ni+64Ni Reaction at 40 AMeV

The multiplicity of fragments in Fermi energy heavy-ion collisions was experimen-tally extracted. Compared with the results of calculation using the antisymmetrized molecular dynamics (AMD) model which accounts for the primary fragments only, the results calculated using the AMD together with a statistical decay code GEMINI to account for the deexcitation of excited primary fragments are in better agreement with those extracted from the experiment. This observation indicates that the experimental multiplicity distribution may be significantly different from those of primary fragments.     

High-Spin States in 141Pm

The high-spin states of 141Pm nucleus have been studied by using in-beam γ-ray spectroscopy technology through the 126Te( 19F, 4n) reaction at a beam energy of 90 MeV. The previous level scheme has been extended with spin up to 49/2 . Many new levels and transitions are identified. Five collective band structures are observed. Based on systematic comparison with the neighboring nuclei, two bands with strong I = 1 M1 transitions inside the bands are proposed as the oblate bands with γ～-60°, and three bands with large signature splitting have been suggested as the oblate-triaxial deformation with γ～-90 °. The characteristics for these bands have been discussed.     

Energy-angle distribution measurements for 0.8v020Ne and 209Bi ions penetrating thin carbon foils

Energy-angle distributions have been measured for 0.8v₀, (v₀ = Bohr velocity) Ne and Bi ions penetrating through carbon foils. Comparing the results with a Monte Carlo computer simulation that included an angle dependence only for the elastic collisions, we have observed for Ne projectiles an angle-dependent inelastic loss which, for small angles, is much larger than the elastic contribution in the case of thin foils. In the case of Bi, the energy loss distribution is dominated by elastic collisions. The calculations of Meyer, Klein and Wedell, and Ellmer and Wedell cannot describe the experimental results. The multiple scattering distributions are in agreement with both analytical and Monte Carlo calculations.     

脉冲离子束作用下金属氚化物氦释放测量技术研究

为认识脉冲离子束作用下金属氚化物的氦释放行为,建立了脉冲离子束作用下金属氚化物氦释放测量系统。利用标准体积气体取样装置,采用气体反扩散法,对系统的容积比、灵敏度进行了实验标定。在此基础上,发展了脉冲离子束作用下金属氚化物氦释放的测量技术,开展了脉冲离子束作用下金属氚化物氦释放实验研究。结果显示,单次脉冲离子束作用下金属氚化物的氦释放呈脉冲式,释放量最大可达10~(13)个原子以上。     

~(88)Kr γ射线发射几率的测量

利用轻质海绵为填充材料,采用小体元分割法制备混合标准源,完成了高纯锗γ探测器对放射性气体源效率的校准。采用活性碳低温吸附法从235 U的裂变产物中快速提取放化纯88 Kr,并制成气体密封源,采用上述校准的高纯锗γ探测器对其进行了实验测量。利用放射性暂时平衡原理,通过子核88 Rb的活度计算得到了88 Kr的活度,进而计算出88 Kr各γ射线的发射几率,其结果的不确定度与评价值相比明显降低。     

时间间隔分析测量低浓度220Rn的实验研究

介绍了一种测量低浓度²²⁰Rn的方法--时间间隔分析方法。²²⁰Rn原子发生衰变发射α粒子并产生²¹⁶Po时,在很短时间内,²¹⁶Po衰变(半衰期0.145 s)又发射α粒子。多时间分析方法就是对2个连续发射的α粒子的时间间隔进行分析,使²²⁰Rn从²²²Rn中分辨出来。本实验通过卢卡斯氡探测器（FD125）对10 Bq的²²⁰Rn标准源进行流气式测量。当²²²Rn活度小于10倍左右²²⁰Rn活度时,计数率控制在60 min^-1以内,时间分辨率设置为1 ms,测量时间为10 h,测量结果的相对偏差在7%内。     

13C同位素的分离工艺设计与实验研究

本文综述了在¹³C同位素的分离研究中建立“数值模拟+实验研究”的工程化研究方法,完成了一氧化碳低温精馏法分离稳定性同位素¹³C的计算机辅助设计,以及低温精馏工程实验研究。通过CO低温精馏单塔实验测定了¹³C同位素分离体系的基础参数;利用计算机辅助设计了¹³C分离二塔级联工艺,并得到了级联装置的优化参数;通过低温精馏分离¹³C二塔级联实验,对优化设计结果进行检验。研究结果表明,课题建立的“数值模拟+实验研究”相结合的工程研究方法可靠,在¹³C同位素分离中得到了实际应用;课题建立的研究方法提高了¹³C同位素分离的设计水平、降低了实验成本、提高了研发效率,为¹³C同位素分离工业化生产装置的设计提供了可靠的技术方法。     

北京地区大气中7Be、137Cs和131I活度浓度分布规律初步研究

介绍了全面禁止核试验条约（CTBT）国际监测系统（IMS）北京核素台站和北京放射性核素实验室的大气气溶胶取样和测量过程;对核素台站和放射性核素实验室的大气气溶胶的长期监测数据进行了统计分析,得到了⁷Be、¹³⁷Cs和¹³¹I活度浓度的分布特点和规律,为深入研究大气中相关放射性核素浓度分布规律奠定了基础。     

被动沉积法测量222Rn/220Rn子体浓度

被动沉积式²²²Rn/²²⁰Rn（Rn/Tn）子体测量对于现场环境Rn/Tn子体浓度调查和环境Rn/Tn暴露剂量评价具有重要意义。本工作利用自行开发的被动沉积式Rn/Tn子体测量仪,对被动沉积式Rn/Tn子体浓度测量方法进行了初步研究,探讨了其基本原理,并分析了其影响因素。研究表明,在粗略反映同一类型环境不同房屋Rn/Tn子体暴露水平差别的情况下,被动沉积法可用于Rn/Tn子体浓度的现场测量。暴露90 d时,本被动沉积式Rn/Tn子体测量仪测量Rn/Tn子体的探测下限分别为0.234 Bq•m^-3和0.424 Bq•m^-3。若将其应用于不同现场环境Rn/Tn子体浓度测量与暴露剂量评价,还需对该方法进行深入细致的研究。     

235UF6和238UF6同位素分子共振能量转移研究

本文利用长程力碰撞理论计算了²³⁵UF₆和²³⁸UF₆同位素分子间ν₃振动能量的近共振碰撞转移过程,得到了不同温度下共振函数随能量差变化的曲线,发现共振函数的宽度随温度的升高而增大。计算了不同温度下共振转移几率和共振转移速率,发现它们随温度的升高而减小。可见,²³⁵UF₆和²³⁸UF₆同位素分子的平动会降低其共振转移几率和共振转移速率,这为激光光化学法分离铀同位素提供了理论依据。     

Gamma-ray emission probabilities of the fission products 144Ce144Pr, 106Rh, 95Zr

The fission products ¹⁴⁴Ce¹⁴⁴Pr, ¹⁰⁶Rh and ⁹⁵Zr play an important role in the burn-up determination of fuel elements by means of γ-ray spectrometry. One of the crucial quantities in this field is the absolute γ-ray emission probability (intensity) for which values available in literature have not the desirable accuracy of 1–2%.By using Ge(Li)-spectrometers of known efficiency and sources calibrated by 4πβ-γ-coincidence methods, we determined absolute γ-ray emission probabilities of ¹⁴⁴Ce¹⁴⁴Pr, ¹⁰⁶Rh and ⁹⁵Zr with an uncertainty of ±1% for the main γ-rays.     

海水中放射性核素238U、232Th、600Co、137Cs浓集实验

采用广东省环境辐射监测中心编制的操作规程《海水中γ核素浓集方法实施细则》分析了环境海水样品的γ放射性核素238U、232Th、60Co、137Cs,该方法的238U、232Th、60Co、137Cs的回收率分别为82.5%、79.3%、80.3%、91.3%;制样放置约90 d后测量238U的数据更准确。     

压水堆中嬗变99Tc和129I的计算研究

选取大亚湾压水堆作为嬗变参考堆,研究在压水堆中嬗变长寿命裂变产物⁹⁹Tc和¹²⁹I的可行性。计算结果表明：在1个换料周期（18个月）内,⁹⁹Tc的最大嬗变率为15.69%,¹²⁹I的最大嬗变率为9.18%。通过对不同堆芯方案进行安全性分析发现：添加⁹⁹Tc和¹²⁹I后,堆芯有效增殖因数k_eff降低且随燃耗变化的幅度变小;堆芯径向中子通量密度分布无明显变化但径向功率峰因子降低;考虑燃料温度系数、慢化剂温度系数、硼微分价值以及控制棒价值等,得出在反应性温度系数及反应性控制方面不会导致安全问题,相反有优化作用。因此,从安全角度分析,在压水堆中嬗变⁹⁹Tc和¹²⁹I是可行的。     

K-shell X-ray cross-section ratios for 1H, 4He and 6Li projectiles on targets from fluorine to titanium

Experimental K X-ray emission ratios have been measured for nine elements ranging from F to Ti (9 ? Z₂ ? 22) using ¹H⁺, and ⁶Li⁺ projectiles. The experimental ratios are in fair agreement with theoretical predictions for the velocity range studied, $\text{?}{}_{\mathrm{k}}\text{\$}\text{?}\text{1}$.     

利用缓发中子法测量235U裂变数的实验研究

缓发中子伴随核裂变产生,通过对它的测量估算核裂变数是一需实验检验的新方法。在中国原子能科学研究院微堆辐照²³⁵U样品,采用³He正比计数器测量缓发中子,并通过缓发中子数反推得到铀样品的总裂变数。利用高纯锗γ谱仪测量被辐照样品发射的缓发γ射线,通过缓发γ射线数得到样品总裂变数。对两种测量方法得到的结果进行了对比和分析,结果表明,用缓发中子法和缓发γ法对同一样品测量的结果一致,缓发中子法可作为一种辅助诊断方法。