Calculated Activity Values Research Articles

Implementation of Novel Evolutional Algorithm for 3-Dimensional Radiation Mapping and Gamma-Field Reconstruction within the Chornobyl Sarcophagus

This work presents the application of a novel evolutional algorithmic approach to determine and reconstruct the specific 3-dimensional source location of gamma-ray emissions within the shelter object, the sarcophagus of reactor Unit 4 of the Chornobyl Nuclear Power Plant. Despite over 30 years having passed since the catastrophic accident, the high radiation levels combined with strict safety and operational restrictions continue to preclude many modern radiation detection and mapping systems from being extensively or successfully deployed within the shelter object. Hence, methods for reconstructing the intense and evolving gamma fields based on the limited inventory of available data are crucially needed. Such data is particularly important in planning the demolition of the unstable structures that comprise the facility, as well as during the prior operations to remove fuel containing materials from inside the sarcophagus and reactor Unit 4. For this approach, a simplified model of gamma emissions within the shelter object is represented by a series of point sources, each regularly spaced on the shelter object’s exterior surface, whereby the calculated activity values of these discrete sources are considered as a population in terms of evolutionary algorithms. To assess the numerical reconstruction, a fitness function is defined, comprising the variation between the known activity values (obtained during the commissioning of the New Safe Confinement at the end of 2019 on the level of the main crane system, located just below the arch above the shelter object) and the calculated values at these known locations for each new population. The final algorithm’s performance was subsequently verified using newly obtained information on the gamma dose-rate on the roof of the shelter object during radiation survey works at the end of 2021. With only 7000 iterations, the algorithm attained an MAPE percentage error of less than 23%, which the authors consider as satisfactory, considering that the relative error of the measurements is ±17%. While a simple initial application is presented in this work, it is demonstrated that evolutional algorithms could be used for radiation mapping with an existing network of radiation sensors, or, as in this instance, based on historic gamma-field data.

Thermodynamic properties of Al in ternary lead-free solder Al-Sn-Zn alloys

AbstractThermodynamic properties of Al were calculated using the molecular interaction volume model (MIVM) by analyzing the activities of components in the constitutive binary Al-Sn, Al-Zn and Sn-Zn subsystems of the ternary lead-free solder Al-Sn-Zn systems. The activities of Al content in the ternary system at three cross-sections with constant molar ratios of Sn:Zn = 2:1, 1:1 and 1:2, respectively, were calculated and compared with available experimental data at 973 K. Based on the agreement between the calculated activity values and corresponding literature data for Al-Sn-Zn alloys and their subsystems, the activity of Al content in the ternary Al-Sn-Zn system was estimated at the same cross-sections and mole ratios in the temperature range of 1073 K to 1373 K, respectively. It has been observed through the computed activity values of Al that the thermodynamic properties of the ternary Al-Sn-Zn systems do not change appreciably with temperature across the molar sections.

Analysis of the H. B. ROBINSON-2 reactor pressure vessel dosimetry benchmark using TRIPOLI-4® Monte Carlo code

This paper presents an analysis of the H.B. Robinson-2 reactor pressure vessel dosimetry benchmark. This benchmark is based on an experiment performed at an operating PWR (Pressurized Water Reactor). It includes measurements for both in-vessel and ex-vessel dosimeters. To enlarge the TRIPOLI-4 ® validation database of neutron attenuation in PWR, an analysis of H.B. Robinson-2 benchmark was carried out using the TRIPOLI-4 ® Monte Carlo code, the DARWIN/PEPIN2 depletion code, the general-purpose point-wise library JEFF3.1.1, and the International Reactor Dosimetry File IRDF-2002. Calculated activity values are compared with measured ones provided in this benchmark. Furthermore, calculated activity values are also compared with results obtained using two calculation schemes: the deterministic code DORT and the BUGLE-96 cross section library on the one hand, and the Monte Carlo code MCNPX and the JEFF3.1.1 cross section library on the other hand.

Calculation of the thermodynamic properties of the Ga-Sb-Tl liquid alloys

The results of the calculation of the thermodynamic properties for liquid Ga-Sb-Tl alloys at the temperature 1073 K are presented in this paper. Initially, the most appropriate thermodynamic model for the investigated system was selected. Based on a comparison of the values calculated by different geometric models (Kohler, Muggianu, Toop, Hillert, Chou) with the existing experimental based data, asymmetric models of calculation were determined to give the best results. The asymmetric nature of the investigated ternary system was additionally confirmed by the Chou similarity coefficient concept. For these reasons, further complete thermodynamic calculations were performed according to the Hillert model in five sections of the ternary Ga-Sb-Tl system from each corner with the mole ratio of other two components being 9:1; 7:3; 5:5; 3:7 and 1:9. The obtained results include integral excess Gibbs energy dependences on composition for all the investigated sections. The calculated activity values at 1073 K for all components are given in the form of isoactivity diagrams. Comparison between the calculated and experimentally obtained gallium activities shows good agreement.

Prediction of the thermodynamic properties for the Ga–Sb–Pb ternary system

The results of some thermodynamic prediction methods applied to the Ga–Sb–Pb ternary system are presented in this paper. The Chou general solution model and the traditional models of Kohler and Toop were included in the calculation for the comparison and discussion. Integral enthalpy of mixing and integral excess Gibbs energy dependences on composition for the 15 investigated cross sections at 973 K and 1073 K, respectively, were obtained according to the applied models. The comparison between the results of the three models shows good mutual agreement. Obtained results were used for the further calculation of partial molar quantities for every component of the investigated ternary system. Calculated activity values at 1073 K for all components are given in the form of isoactivity diagrams.

Validation of Neutron Fluence Calculation Methodology for VVER-440 Vessel

Validation of neutron fluence on VVER-440 pressure vessel methodology is performed by comparative analysis of calculational compared with experimental results for the induced activity of scraps taken out from the inner surface of the VVER reactor pressure vessel after the 14th and 17th cycles. The mean deviation of 9% between the experimental and the calculated activity values is evaluated. The good consistency of the results demonstrates the validity of the neutron fluence calculational methodology.

Computer‐Assisted Prediction of Bioactive Compounds Based on the Hansch‐Fujita Analysis

AbstractComputer programs called PREHAC1 and PREHAC2, which aid in the impartial selection of substituents for the synthesis of highly bioactive compounds among congeners based on the Hansch‐Fujita analysis, were developed. The PREHAC1 and 2 programs are for aliphatic and aromatic monosubstituted derivatives and for aromatic disubstituted derivatives, respectively. Thirteen sets of physicochemical parameter values of 408 useful substituents were previously input into a data file as Master Data. PREHAC programs are activated by the input of the coefficients and intercept of the QSAR equation with the corresponding parameter codes, the information on the number of the substituents to be printed out, etc., and then Master Data is searched. Calculated activity values are ranked in descending order and the high‐ranking substituents are printed out according to the specified number. An example is presented to illustrate the programs.