在某放射性废物焚烧站退役前,进行源项调查,以掌握现场放射性辐射水平及污染分布情况、进行放射性盘存量估算.调查以辐射测量为主、资料收集为辅.调查发现,现场沉积物项及个别工艺设备明显存在污染,设施内辐射水平和表面污染总体较低,现场同时具有明显的α/β表面污染,设施四周土壤含有微量U污染,放射性盘存量估算结果为9.27×107.焚烧站退役施工中,应注重对表面污染和内照射的防护,应对现场主要源项进行优先处理,同时,采取措施防止污染扩散,实现辐射防护最优化及废物的最小化.

90Sr是高毒性的纯β放射性核素,其物理半衰期和生物半衰期长,环境气溶胶中的90Sr通过吸入途径进入人体,对人类的危害主要为长时间积集在人体骨骼中并很难排出.在多堆型核设施运行场址中环境气溶胶的测定是辐射环境监测的重要内容,也是评价核设施运行对环境影响的重要指标.为了科学评价环境气溶胶中测量结果的准确性和可靠性,进行了气溶胶中90Sr分析测量不确定度评定的方法研究,通过计算模型识别不确定度的来源,并对各分量进行量化分析,计算合成标准不确定度;结合典型样品分析实例,对环境气溶胶中90Sr分析测量的不确定度进行了评定,气溶胶中的分析测量采用的是色层萃取的方法,利用草酸钇沉淀制成样品源,测量样品中β计数率.不确定度评定结果表明:环境气溶胶中90Sr分析测量不确定度的来源主要有样品净计数率,探测效率,化学回收率,样品取样体积,测量期间半衰期修正;典型实例分析结果显示环境气溶胶中的相对标准不确定度可控制在15％内.文章中不确定度评定方法为气溶胶90Sr分析测量结果的不确定度评定提供参考.

建立了 P型同轴型HPGe探测器的探头模型,利用标准源验证模型的准确性,计算了不同高度和不同密度下环境土壤样品中60Co的探测效率值,拟合了探测效率曲线公式,给出了 P型同轴型HPGe探测器测量环境土壤样品中60Co活度的无源效率刻度方法.经验证,此方法的计算值与标准源刻度值的相对偏差在3％以内,证明了该方法的准确性.

介绍了基于点源空间效率函数的层析γ扫描(TGS)无源效率刻度方法.利用TGS系统MC-NP模型计算探测空间120 cm×60 cm×50 cm和γ能量0.01～1.408 MeV的点源空间效率,建立点源空间效率函数及参数,采用体素中心点源效率等效法,实现体素效率矩阵计算.结果表明:5种γ能量在探测空间507个位置处的效率测量值和函数计算值具有较高相关性,说明该方法能够准确、快捷地实现TGS体素无源效率刻度.

针对200 L核废物桶分段γ扫描(SGS)过程中的效率刻度问题,提出了一种效率刻度函数模型,采用MCNP程序计算不同基质密度和γ射线能量条件下的离散断层效率,经过多元非线性回归获取函数参数,从而建立效率刻度函数,实现核废物桶SGS断层效率刻度.对核废物桶样品进行实验分析,结果表明:对于桶内基质分别为密度0.310 g·cm?3的硅酸铝、密度0.595 g·cm?3的木质纤维,桶内核素分别为活度3.110×105 Bq的点源137Cs、活度1.371×105 Bq的点源60Co,在桶内仅有单个点源存在的核素分布极端不均匀情况下,桶内核素活度重建误差在?37.68％～31.52％范围内.本文的方法能够准确有效实现核废物桶SGS断层效率矩阵计算,并确定核废物桶内放射性核素活度,满足实际检测要求.

移动式屏蔽检查热室可模块化地拆卸、运输、组装并实现简单检查功能,具备了较好的机动性和灵活性.但同时,由于要兼顾机动性和灵活性,带来了辐射防护工作实施的一系列新问题.为解决相关问题,本文在参考现有核设施辐射防护体系建设标准的基础上,梳理了移动式屏蔽检查热室辐射防护剂量限制体系,开展了移动式屏蔽检查热室辐射防护解决方案研究,从源项及屏蔽、通排风、辐射分区及管理、辐射监测、事故处理等要素进行了相关细化考虑.

Radioactive waste sampling glove box can reduce the damaging effects of radiation distilled residue of staff,in order to meet the requirements of radiation protection and optimization, to determine the thickness of the shield glove box,making the integrated irradiation due to personal total effective dose not to exceed the dose limit at the same value and achieve optimal levels is very important. In this paper, MCNP procedures for stainless steel glove box shielding calculations are applied to the cost-benefit analysis of radioactive waste derived optimal sampling glove box shielding layer thickness.

In order to study the technology of fuel element rupture monitoring further,the test of the online monitoring device for fuel element rupture on HFETR was done.This paper described the test results and analysis.The iodine well phenomenon and xenon poisoning phenomenon were found,and there were agreed with theory.Moreover,the monitoring results of the prototype also accord with laboratories results.So the test results confirmed that the device have a ability of monitoring target nuclides in primary loop.

To better assess the environmental behavior and effect of uranium on living organisms more accurately, herein, Na-bentonite was used as an adsorbent for the immobilization of uranium from radionuclide polluted wastewater. The experimental results demonstrated that sorption dynamics of U(VI) on the Na-bentonite could obtain equilibrium in a time period of 10h. The sorption performance of U(VI) on the surface of Na-bentonite material was strongly dependent on pH values of solution. The sorption of U(VI) was influenced by ionic strength at pH<7.5, whereas was independent of ionic strength at pH>7.5. The presence of fulvic acid (FA) or humic acid (HA) promoted the sorption behavior of U(VI) onto Na-bentonite at low pH values while suppressed the sorption performance at high pH values. The thermodynamic coefficients (i.e., ΔS0, ΔG0 and ΔH0) calculated from the temperature-dependent sorption isotherms illustrated that sorption process of U(VI) on the Na-bentonite was spontaneous and endothermic. At low pH values, the sorption performance of U(VI) was dominated by outer-sphere surface complexation and ion exchange with Na+/H+ on Na-bentonite surfaces, whereas inner-sphere surface complexation and co-precipitation were the main sorption mechanism at high pH values. Considering its high physicochemical stability and high removal performance property, the prepared Na-bentonite can be used as a cost-effective and potential adsorbent for the immobilization and recovery of U(VI) from large volumes of aqueous solutions.

Magnetic multiwalled carbon nanotube/iron oxide composite (Fe3O4/MWCNT) was synthesized as an adsorbent for the preconcentration of U(VI) from aqueous solutions. The surface properties of Fe3O4/MWCNT were characterized via adopting FTIR, SEM and potentiometric acid–base titration. The sorption behaviors of U(VI) on the surface of Fe3O4/MWCNT were investigated under environmental conditions by using batch technique, such as pH, ionic strength and contact time. The pH-dependent U(VI) sorption behavior on Fe3O4/MWCNT illustrated that sorption mechanism of U(VI) was achieved by outer-sphere surface complexation at low pH values, while the sorption of U(VI) was achieved by inner-sphere surface complexation and simultaneous precipitation at high pH values. Besides, the pH-dependent sorption also demonstrated an optimal and feasible pH value of 7.0 by adopting Fe3O4/MWCNT in the preconcentration of U(VI) from aqueous solutions. The sorption kinetic experimental data could be well simulated by using the pseudo-second-order pattern. The Langmuir and Freundlich patterns were employed to simulate sorption isotherms of U(VI) at three different temperatures, the experimental results demonstrated that sorption process was favorable at higher environmental temperature. The maximum sorption capacity of U(VI) on Fe3O4/MWCNT was higher than that of major materials reported. Related experimental data further indicated that Fe3O4/MWCNT had satisfactory treatment performance for the simulated wastewater. The Fe3O4/MWCNT particles having strong magnetism could be favorably and easily separated from aqueous solution under an external magnetic field. The correlative experimental results further demonstrated that the Fe3O4/MWCNT composite could be a promising adsorbent for the preconcentration of radionuclides from large volumes of aqueous solution.