This study introduces the process and methodology for determining residual radioactive levels in soil at a decommissioned nuclear facility site. Drawing on current research into decommissioned sites both domestically and internationally, this study reviews the approaches adopted by the International Atomic Energy Agency, the USA, and China for defining decommissioning end-state targets and establishing dose constraint values. A source investigation of soil pollution was first conducted to identify the types and quantify the activity concentrations of key pollutants. Subsequently, the radiological assessment defined decommissioning goals and dose constraints, identified exposure pathways and key parameters under open, unrestricted land-use scenarios, and developed an assessment model to calculate the effective dose using a forward calculation approach. By using the open-limit conversion method for reverse calculation, the residual radioactive level of the decommissioned final soil is ultimately determined. The allowable residual activity concentration values for three nuclides were calculated. The allowable residual activity concentration value for ^{60}\mathrm{Co} was 1.9 \cdot 10^{2} \, \mathrm{Bgkg^{-1}} , the allowable residual activity concentration value for ^{137}\mathrm{Cs} was 8.4 \cdot 10^{2} \, \mathrm{Bgkg^{-1}} , and the allowable residual activity concentration value for ^{90}\mathrm{Sr} was 1.1 \cdot 10^{5} \, \mathrm{Bgkg^{-1}} . The final determination of the allowable residual activity concentration values for the three nuclides will provide a basis for implementing, supervising, and accepting decommissioned engineering projects.
The advent of high-intensity, high-polarization electron beams led to significantly improved measurements of the ratio of the proton's charge to electric form factors, GEp/GMp. However, high-$Q^2$ measurements yielded significant disagreement with extractions based on unpolarized scattering, raising questions about the reliability of the measurements and consistency of the techniques. Jefferson Lab experiment E01-001 was designed to provide a high-precision extraction of GEp/GMp from unpolarized cross section measurements using a modified version of the Rosenbluth technique to allow for a more precise comparison with polarization data. Conventional Rosenbluth separations detect the scattered electron which requires comparisons of measurements with very different detected electron energy and rate for electrons at different angles. Our Super-Rosenbluth measurement detected the struck proton, rather than the scattered electron, to extract the cross section. This yielded a fixed momentum for the detected particle and dramatically reduced cross section variation, reducing rate- and momentum-dependent corrections and uncertainties. We measure the cross section vs angle with high relative precision, allowing for extremely precise extractions of GEp/GMp at $Q^2$ = 2.64, 3.20, and 4.10 GeV$^2$. Our results are consistent with traditional extractions but with much smaller corrections and systematic uncertainties, comparable to the uncertainties from polarization measurements. Our data confirm the discrepancy between Rosenbluth and polarization extractions of the proton form factor ratio using an improved Rosenbluth extraction that yields smaller and less-correlated uncertainties than typical of previous Rosenbluth extractions. We compare our results to calculations of two-photon exchange effects and find that the observed discrepancy can be relatively well explained by such effects.
As a historic challenge for humans, Martian colonization has been initiated by nuclear energy. A moving nuclear power plant could be imaginable known as a nuclear reactor rover. The design of the nuclear reactor rover has been performed where the important matter is how to make the caterpillar move the reactor and its facilities. Hence the slider length and contact point are proposed. The normalized heat transfer is analyzed by slide length and contact point where they are normalized as 1.0 and 10.0, respectively. Although the slider length of the caterpillar is proportional to heat transfer, the contact point shows the adverse values. Longer slider length and less contact point could be the optimized heat production system by the caterpillar which is the additional heat source except the other nuclear reactor. Any other planet could be considered as a potential human colony using the nuclear terraforming technology.
This work addresses the problem of propagating uncertainty from group-wise neutron cross-sections to the results of neutronics diffusion calculations. Automatic differentiation based on dual number arithmetic was applied to uncertainty propagation in the framework of local sensitivity analysis. As an illustration, we consider a two-group diffusion problem in an infinite medium, which has a solution in a closed form. We employ automatic differentiation in conjunction with the sandwich formula for uncertainty propagation in three ways. Firstly, by evaluating the analytical expression for the multiplication factor using dual number arithmetic. Then, by solving the diffusion problem with the power iteration algorithm and the algebra of dual matrices. Finally, automatic differentiation is used to calculate the partial derivatives of the production and loss operators in the perturbation formula from the adjoint-weighted technique. The numerical solution of the diffusion problem is verified against the analytical formulas and the results of the uncertainty calculations are compared with those from the global sensitivity analysis approach. The uncertainty values obtained in this work differ from values given in the literature by less than 1?10?5.
A. N. Ivanov, R. Höllwieser, N. I. Troitskaya
et al.
We calculate the contributions of weak magnetism and proton recoil of order O(E^2_e/m^2_N)~10^{-5}, i.e. to next-to-next-to-leading order in the large nucleon mass expansion, to the neutron lifetime and correlation coefficients of the neutron beta decay, where E_e and m_N are the electron energy and the nucleon mass, respectively. We analyze the electron-energy and angular distribution for the neutron beta decay with a polarized neutron, a polarized electron and an unpolarized proton. Together with Wilkinson's corrections (Nucl. Phys. A 377, 474 (1982) and radiative corrections of order O(alpha E_e/m_N) ~ 10^{-5} (Phys. Rev. D 99, 093006 (2019)), calculated as next--to--leading order corrections in the large nucleon mass $m_N$ expansion to Sirlin's corrections of order O(alpha/pi) (Phys. Rev. 164, 1767 (1967)), the corrections of order O(E^2_e/m^2_N) ~ 10^{-5} provide an improved level of precision of the theoretical background of the neutron beta decay, calculated in the Standard Model, for experimental searches of contributions of interactions beyond the Standard Model.
Aybaba Hancerliogullari, Madee Ali, Ash Kurnaz
et al.
Sepiolite is a naturally occurring clay mineral of sedimentary origin and is a magnesium hydrosilicate. Sepiolite has been widely used as an additive raw material in ceramics and cement industry, pharmaceutical, cleaning-detergent, paper, paint, cosmetic agriculture, fertilizer, etc. In this study, the natural radioactivity levels, radon emanation coefficients and radon exhalation rates of 30 sepiolite samples collected from open three sepiolite quarries (Beylikova, Polath and Sivrihisar) in Central Anatolia region of Turkey were determined by using a gamma-ray spectrometry with an HPGe detector. The average absorbed gamma dose rates directly measured in Beylikova, Polath and Sivrihisar open three sepiolite quarries located in Central Anatolia region of Turkey were found as 59, 65, and 64 nGyh?1, respectively. The average activity concentrations of 226Ra, 232Th, and 40K in 30 sepiolite samples collected from those quarries were found as 38.6, 12.4, and 67.4 Bqkg?1, respectively. The average emanation coefficient and exhalation rate of radon of sepiolite samples were determined as 22 % and 0.065 Bqkg?1h?1, respectively. Also, radiological parameters (outdoor absorbed gamma dose rate, annual effective dose rate, external and internal index) were estimated to evaluate the use of sepiolite samples as additive raw materials in the building sector.
Nikola Mihaljevic, Slobodan Jovanovic, Aleksandar Dlabac
Efficiency calibration, i. e. determination of detection efficiency, ?p, is a crucial issue in gamma spectrometry (quantification of gamma spectroscopic measurements) with semiconductor and scintillation detectors. Comparing three possible ways to addressing the problem ? relative, absolute and semi empirical ? advantages of the latter are emphasized. Among semi empirical models, efficiency transfer using effective solid angles, ??, is sorted out and briefly elaborated. This approach reduces the problem of efficiency calibration to the determination of ??. It proved reliable and has been broadly used in practice, mainly in the form of the long existing ANGLE software. Progressing further, a generalized mathematical formula for calcu- lations is developed ? first of the kind ? offering an opportunity for advanced applications of gamma spectrometry. The formula enables unlimited flexibility in application, as it conveniently separates the source data from the detector data during the integration procedures ?? calculations). Its practicality is demonstrated for a number of typically encountered counting arrangements, as well as for some exotic ones. The relevant formulae are used in PC calculations and numerical testing is further performed so as to check the validity of the mathematical method and the computer code. Care was taken of the optimization of complex numerical procedures employed (involving fivefold numerical integration), so as to keep computation times as low as possible (in order of minutes or even seconds on ordinary PC). Results obtained are affirmative for both the method and the code. The model will be gradually incorporated into ANGLE software, thus making it readily available for routine use by gamma spectrometry community.
A. N. Ivanov, R. Höllwieser, N. I. Troitskaya
et al.
We analyze the contributions of the one-pion-pole (OPP) exchange, caused by strong low-energy interactions, and the pseudoscalar interaction beyond the Standard Model (BSM) to the correlation coefficients of the neutron beta-decays for polarized neutrons, polarized electrons and unpolarized protons. The strength of contributions of pseudoscalar interactions is defined by the effective coupling constant C_ps = C^(OPP)_ps + C^(BSM)_ps. We show that the contribution of the OPP exchange is of order C^(OPP)_ps ~ - 10^(-5). The effective coupling constant C^(BSM)_ps of the pseudoscalar interaction BSM can be in principle complex. Using the results, obtained by Gonzalez-Alonso et al.( Prog. Part. Nucl. Phys. 104, 165 (2019)) we find that the values of the real and imaginary parts of the effective coupling constant C^(BSM)_ps are constrained by - 3.5x10^{-5} < ReC^(BSM)_ps < 0 and ImC^(BSM)_ps < - 2.3x10^(-5), respectively. The obtained results can be used as a theoretical background for experimental searches of contributions of interactions BSM in asymmetries of the neutron beta-decays with a polarized neutron, a polarized electron and an unpolarized proton at the level of accuracy of a few parts of $10^{-5}$ or even better (Abele, Hyperfine Interact.237, 155 (2016)).
Rameshwar Bhosale, Chaitali More, Dhammajyot Gaikwad
et al.
In the present work we investigated the gamma radiation parameters as mass attenuation coefficients ?/?, the total atomic scattering cross-sections ??, the electronic scattering cross-sections se, the effective atomic numbers Zeff, and the effective electron densities Neff for some polymers such as polyoxymethylene (CH2O), poly acrylonitrile (C3H3N), natural rubber (C5H8), poly ethyl acrylate (C5H8O2), polyphenyl methacrylate (C10H10O2), and polyethylene tetraphthalate (C10H8O4). The gamma ray photons were detected by NaI(Tl) detector with resolution of 8.2 % at 662 keV, using radioactive gamma ray sources 57Co, 133Ba, 137Cs, 54Mn, 60Co, and 22Na at energies 122, 356, 511, 662, 840, 1170, 1275, and 1330 keV. Values of ?/? for the chosen polymers decrease with increasing energy. The results of investigated data are useful in plastic industry, building materials, agriculture fields radiation shielding, accelerator centers, polymer industry, medical field, etc.
Leila Ramezani, Masoud Mansouri, Mohammad Rahgoshay
Zirconium alloys, are usually used as fuel cladding materials in VVER (water-cooled, water-moderated energy reactor) type reactors, mainly, due to their low neutron absorption cross-section, desirable mechanical properties, and good corrosion resistance under reactor operating conditions. During exposure to water at high temperature, water reacts with zirconium alloys, which results in the production of an oxide layer. The entire area of corrosion along with the accompanying absorption of hydrogen in the zirconium metal matrix has attracted a lot of attention when the performance of the core components as well as the operation of the reactor is emphasized. The growth of the zirconium oxide layer plays a destructive role in decreasing thermal efficiency of the reactor by restricting the inlet temperature and chemical properties of the coolant. The present study aimed to develop a computer code to predict long-term water side corrosion weight gain, oxide thickness and determine the concentration of absorbed hydrogen in VVER-1000 reactors during normal operating conditions. The proposed model can be utilized to estimate the pre-transition and post-transition corrosion weight gain and the oxide thickness in operating conditions.
Aldo Parlato, Elio Tomarchio, Cristiano Calligaro
et al.
The methodology, developed for active testing of electronic devices under the radiations, is presented. The test set-up includes a gamma-ray facility, the hardware board/fixtures and the software tools purposely designed and realized. The methodology is so wide-ranging to allow us the verification of different classes of electronic devices, even if only application examples for static random access memory modules are reported.
The manuscript clarifies the issues concerning the effective miniaturization of readout of the plastic scintillators while maintaining their high detection efficiency and sensitivity. Values obtained from the measurements of the chosen gamma emitters (60Co, 137Cs, 241Am), at various distances, were used to compare the detection efficiencies. The organic plastic scintillators, with the ternary system of different shapes and volumes, were chosen for the measurement. The detection parameters for the examined 1" PMT, with variable photocathode geometry, were experimentally found and compared to the normally used 2" PMT, with the circular type of photocathode. The primary aim of this work was to verify whether, in the case of mobile applications, such as UAV, it is possible to replace the currently bulky and quite heavy electronics with a miniature version and simultaneously preserve their detection parameters.
The stability analysis of a nuclear reactor is an important aspect in the design and operation of the reactor. A stable neutronic response to perturbations is essential from the safety point of view. In this paper, a general methodology has been developed for the linear stability analysis of nuclear reactors using the lumped reactor model. The reactor kinetics has been modelled using the point kinetics equations and the reactivity feedbacks from fuel, coolant and xenon have been modelled through the appropriate time dependent equations. These governing equations are linearized considering small perturbations in the reactor state around a steady operating point. The characteristic equation of the system is used to establish the stability zone of the reactor considering the reactivity coefficients as parameters. This methodology has been used to identify the stability region of a typical pressurized heavy water reactor. It is shown that the positive reactivity feedback from xenon narrows down the stability region. Further, it is observed that the neutron kinetics parameters (such as the number of delayed neutron precursor groups considered, the neutron generation time, the delayed neutron fractions, etc.) do not have a significant influence on the location of the stability boundary. The stability boundary is largely influenced by the parameters governing the evolution of the fuel and coolant temperature and xenon concentration.