核素在非饱和黄土介质中的二维迁移

试验结果表明，天然降水条件下，在近3年的试验期间，^60Co,^85Sr和^134Cs三种核素在非饱和黄土介质中的比活度分布质心仍在示中源层这内，^85Sr的侧向比活度分布方差与纵向比活度分布方差相当；在人工喷淋条件下，这些核素的迁移距离也很短，说明非饱和黄土对这些核素有较强的吸附滞留能力。或者换句话说，非饱和黄土可以作为中低放废物处置的候选地质介质。另外，根据对试验结果的拟合与分析看出，降水入渗量极大地影响着核素向下的迁移速度和纵向扩展，因此，控制流经处置库的入渗水量，是减少处置废物中放射性核素对环境影响的重要因素。     

Mathematical simulation of radionuclide migration in freezing-thawing soils

Mathematical models of the migration of radionuclides taking account of a phase transition of the interstitial solution in soil are proposed. The moisture-transport equation can be represented in moisture and potential forms. The results of a long-time comparative numerical experiment checking the effectiveness of the proposed models using special methods of numerical simulation are presented.Translated from Atomnaya Énergiya, Vol. 97, No. 5, pp. 374–380, November, 2004.     

Vertical soil migration of radionuclide fallout from the Chernobyl' accident

Translated from Atomnaya Énergiya, Vol. 66, No. 3, pp. 194–197, March, 1989.     

放射性核素迁移的包气带-饱和带耦合模拟研究

为了使地下水环评结果更加真实,通过试验和拟三维方法数值模拟开展包气带-饱和带耦合模拟工作。为进一步说明包气带对核素迁移的迟滞(延迟和滞留)作用,开展了不考虑包气带的模拟并与耦合模拟结果对比。结果表明:(1)由于包气带对核素迁移的迟滞作用,吸附性较强的Se-79、Pd-107、Cs-135和Sn-126迁移至潜水面处的浓度远小于泄漏的放射性液体核素浓度,所致公众食入年待积有效剂量已小于剂量限值0.1 mSv,只有吸附性较弱的C-14所致公众食入年待积有效剂量大于0.1 mSv,需进行耦合模拟;(2)C-14在对流作用下不断向下游迁移,在弥散作用下污染范围逐渐增大,在地下水稀释及衰变、吸附作用下浓度逐渐降低。通过耦合模拟得到的地下水中放射性核素所致公众食入年待积有效剂量小于剂量限值0.1 mSv;(3)包气带对核素迁移的迟滞作用使地下水中C-14的浓度大大降低、迁移距离明显变小:地下水中C-14峰值浓度在考虑包气带时为2.15 Bq/L,不考虑包气带时为9.4×10⁴ Bq/L;事故发生后第1、5和10年,考虑包气带时C-14迁移距离分别为1.5 m、4 m和4.2 m,不考虑包气带时分别为3 m、12 m和17 m。     

Modelling the effect of diffusion into the rock matrix on radionuclide migration

Diffusion into the rock matrix is potentially an important retardation mechanism for nuclides leached from an underground radioactive waste repository in a fractured hard rock. Models of this diffusion process are discussed and incorporated into three-dimensional radionuclide migration models. Simple solutions to these models are derived for two regions: the region near to the repository where the nuclide is diffusing into effectively infinite rock, and that much further downstream where the concentrations in the rock and fractures are almost in equilibrium. These solutions are used to evaluate the possible impact of migration. It is shown that retardation factors in excess of 100 and reductions in the peak concentration at a given point on the flow path by three or four orders of magnitude are possible for non-sorbed ions, which would otherwise be carried by the flow and not retarded at all.     

Response function of the convection-dispersion equations describing radionuclide migration in a finite medium

Analytical expressions are derived for the response functions for the set of n coupled convection-dispersion equations in 1-D with constant coefficients. The equations are solved for a finite medium, and for an n-member radioactive decay chain with radionuclide-specific retardation factors. An exponential transformation and the Laplace transformation are applied to this set of partial differential equations to obtain a general set of transformed solutions. These are then inverted by two procedures to produce complementary forms of the response functions. One form converges quickly for small values of dimensionless time while the other converges quickly for large values. These response functions are used to model radionuclide transport in an underground nuclear waste disposal vault.     

Response functions of the convection-dispersion equations describing radionuclide migration in a semi-infinite medium

Analytic expressions are derived for the response functions for the set of n coupled convection-dispersion equations in 1-D and with constant coefficients, for an n-member radioactive decay chain. The one-sided Laplace transform is applied to this set of partial differential equations, and eigen vectors and eigen values of the resulting system of equations are used to obtain general expressions for the Laplace transforms of the response functions. These are then inverted to produce analytic expressions for the response functions. These are used to solve problems with arbitrary time-varying boundary condition using convolutions. Laplace transforms of systems having similar characteristics can be written readily using results presented in this paper.     

放射性废物处置中核素迁移研究现状及展望

放射性废物根据分类标准采取不同的处置方式。放射性核素具有半衰期长、放射性强等特点,调研了国内、外低、中、高放射性核素处置研究的工作进展,并从核素种类、黏土类型、具体迁移研究方法、研究设备方面,总结了当前国内、外的研究现状,对我国放射性废物处置中的核素迁移工作提出了相应的建议。     

Calculation of fuel burnup and radionuclide inventory in the Syrian miniature neutron source reactor using the GETERA code

Calculations of the fuel burnup and radionuclide inventory in the Syrian miniature neutron source reactor (MNSR) after 10 years (the reactor core expected life) of the reactor operation time are presented in this paper using the GETERA code. The code is used to calculate the fuel group constants and the infinite multiplication factor versus the reactor operating time for 10, 20, and 30 kW operating power levels. The amounts of uranium burntup and plutonium produced in the reactor core, the concentrations and radionuclides of the most important fission products and actinide radionuclides accumulated in the reactor core, and the total radioactivity of the reactor core were calculated using the GETERA code as well. It is found that the GETERA code is better than the WIMSD4 code for the fuel burnup calculation in the MNSR reactor since it is newer, has a bigger library of isotopes, and is more accurate.     

Calculation and measurement of migration coefficient of radon under laboratory conditions

Under laboratory conditions （i.e. a sealed system in which the temperature may vary according to air temperature）, the migration of radon in upward, downward and horizontal directions has been investigated. After a period of accumulation, the spatial distribution profile of radon was drawn on the basis of the experimental data. The profile showed whorl-shape with bigger ends. The longer the accumulation time, the bigger the whorl end, and the higher the radon concentration is. By fitting the experimental data by least-square statistical method, we find that the distributions of radon follow negative exponential functions in the upward, downward and horizontal directions. However, exponents for the three directions are not exactly identical. The upward migration is more effective than the downward one and both upward and downward migrations are more effective than the horizontal one.     

The forms in which certain fission products reach the earth's surface

It was found that the distribution of certain radioactive isotopes between the soluble and insoluble fractions of radioactive fallout is determined by the chemical properties of the isotope, the quantity of solid phase, the type of fallout, and its physical state. The isotopes which were studied occurred in solution in the order Sr⁹⁰>Cs¹³⁷>C¹⁴⁴.Although most of the radioisotopes in the soluble part of fallout are present as cations (for a l i types of fallout the averages are 59% (Ce¹⁴⁴), 75% (Sc¹³⁷) and 86% (Sr⁹⁰ a considerable fraction is present in anion or neutral form. The ratio between the forms depends on the chemicaI properties of the element and the chemical composition of the solution.Radioisotopes occurring in the insoluble fraction of the fallout can also take part in the processes of migration in soil and vegetation. The greatest mobility from the solid phase is shown by Sr⁹⁰ the least by Ce¹⁴⁴.Translated from Atomnaya Énergiya, Vol. 20, No. 4, pp. 333–337, April, 1966.     

某矿山天然放射性核素的调查

对某矿山工作场所和生活区分别进行了样品采集,并使用ORTEC公司生产的16000道HPGeγ能谱仪进行了测量。结果表明,该矿山工作场所天然放射性核素的比活度大多高于生活区,其中危害最大的为尾矿坝;某些生活区天然放射性核素的比活度比对照点和国家均值要高,但多数都在国家均值范围内,最高值出现在3号生活区的农田土样中,其天然放射性核素的比活度分别为:a(226Ra)——750.4Bq/kg、a(232Th)——91.5Bq/kg、a(40K)——1202Bq/kg。     

Monitoring the radionuclide body burden of humans

Translated from Atomnaya Énergiya, Vol. 68, No. 3, pp. 208–209, March, 1990.     

建筑材料中放射性核素限量标准的探讨

《建筑材料放射性核素限量》（GB6566—2001）结束了我国建材标准长期不统一的局面，规定了对建材中放射性实现强制检定的要求，但在装修材料分类、空心材料、废渣利用、测量方法等方面存在着一些不合理的规定。与以往的国家标准相比。对建材中的放射性控制明显放宽，甚至比原来的建材行业标准对石材的控制还要宽，影响了公众的辐射防护安全。对此进行了详细的分析和讨论。