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[en] The effective Radiation Protection Programme (RPP) for Nuclear Power Plant (NPP) is a crucial factor for protecting workers, public, and the environment against the radiological hazards a raised during the lifetime of the nuclear power plant. In this research an Operational Radiation Protection Programme (ORPP) has been designed based on the regulations and the requirements of the Sudanese Nuclear and Radiological Regulatory Authority (SNRRA) as well as on the requirements and the radiation safety guides of the International Atomic Energy Agency (IAEA), The designed ORPP covered the areas of; Assignment of responsibilities, Classification of working areas, Local rules and supervision of work, Protective clothing and personal protective equipment, Facilities, shielding and equipment, Removal or reduction in intensity of sources of radiation, Work planning and work permit, Monitoring and dose assessment, Health surveillance, Release Consequence Assessment, Emergency planning and response, Information and Training, Quality assurance, Audits and review . The designed ORPP was compared with the requirements of a number of international and regional regulatory bodies as well as with those of the operational radiation protection programme for the research reactor at the reactor center of National Nuclear Research Institute (NNRI) of the Ghana Atomic Energy Commission, to ensure the effectiveness of the designed ORPP. The Pressurized Water Reactor (PWR) manufactured by Wasting House is considered to be the type of the reference NPP upon which the ORPP is designed. (Author)
[en] In this article, we are presenting the results of model calculations for (n,p) and (n,2n) reaction cross sections using the standard nuclear reaction codes TALYS-1.8 and EMPIRE-3.2 for 67,70Zn, 92,96,100Mo and 208Pb isotopes in neutron energy range 0-20 MeV. Different nuclear level density models and optical model potential available in the codes have been tested for the estimation of cross sections of desired nuclear reactions. Moreover, in this work, the contribution to the cross section from different reaction mechanisms such as compound nucleus process, pre-equilibrium emission and direct reaction is also discussed in detail. The calculated results are compared with the existing experimental data from the IAEA-EXFOR database. (author)
[en] Light emitting diodes based on gallium arsenide-phosphide solid solutions were studied. Negative differential resistance regions were identified at lower temperatures T ≤ 130 K. Irradiation of diodes by electrons (E = 2 MeV) leads to the increase in the differential resistance, change in the contact potential difference, and a drop in the radiation intensity. These effects are due to the influence of deep radiation defects levels and surface states, activated by high levels of the ionization excitation peculiar to electron irradiation. (author)
[en] The procedure of fracture resistance calculation for WWER primary equipment components has been improved. In particular, this refers to the reactor pressure vessel (RPV) and steam generators (SG) under normal operating conditions and emergencies. The developed calculation procedures and software make it possible to determine the significant effect of such factors as deformation stress history, residual technological heredity, analysis of temperature dependence of stress intensity factors for the postulated crack, regularity and density of the finite element mesh in the crack front on the assessment of WWER-1000 RPV fracture resistance.The paper proposes the methodology for justifying the place and orientation of the postulated crack to obtain the most conservative assessment of fracture resistance in the area of RPV inlet nozzles. It is shown that elastoplastic calculations in the thermal shock simulation can help to improve estimates of RPV strength and lifetime..It was established that not taking into account the elastoplastic deformation history, residual technological stresses after heat treatment and corrosion effects can result in non-conservative assessment of fracture resistance of coolant header welding to SG PGV-1000M shell under normal operating conditions and emergencies.The calculation methodology and software for assessing stress-strain state of in-vessel internals were improved taking into account state-of-the-art approaches to modeling of radiation-induced swelling deformations and dependence of metal mechanical peculiarities on exposure doses and temperature
[en] Highlights: • The method described in this paper defines a selective means to prepare large quantities of 147Pm. • Pm-147 can be produced via β– decay of 147Nd produced via 146Nd[n,γ]147Nd(t1/2 = 10.98 d, β–)147Pm nuclear reaction. • Separation of 147Pm from mg amount of Nd target via extraction chromatography is described. • For 24-d irradiation at ORNL-HFIR, 147Pm yield reaches a maximum value of 101.8 MBq/mg (2.75 mCi/mg) at 60 d post EOB. • Because of large neutron capture cross-sections of 147Pm, the yield of 147Pm does not significantly increase with longer irradiation. - Abstract: In this paper, we describe the 147Pm production yields and level of impurities from several targets that consisted of milligram quantities of highly enriched 146Nd oxide irradiated at the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory for durations ranging from 24 to 180 h. A comparison between theoretical and experimental data are also presented, and attempts were made to empirically evaluate the neutron capture cross-sections of 41.3-d 148mPm and 5.4-d 148gPm. For a one-cycle irradiation (~24 days), 147Pm yield reaches a maximum value of 101.8 MBq/mg (2.75 mCi/mg) at 60 days after the end of bombardment. Because of large neutron capture cross-sections of 147Pm, the yield of 147Pm does not significantly increase with longer irradiation. Our estimates of the thermal neutron capture cross-section and resonance integral for 146Nd at 1.48 ± 0.05 b and 2.56 ± 0.25 b, respectively, were consistent with the reported values. The effective neutron capture cross-section of 147Pm to 148mPm was 53.3 ± 2.7 b–a factor of 2 lower than the 98.7 ± 6.5 b calculated from reported cross-sections. The measured σeff to the ground state (5.37-d 148gPm) was 82.0 ± 4.1 b; ~34% lower than the value of 139 ± 10 b calculated from reported cross-sections. In this work, we also describe the development of a chemical process based on extraction and ion-exchange chromatography for separation of 147Pm from milligram quantities of 146Nd and other impurities. Sequential separation of Pm from the Nd target and from other radioisotopic impurities (153Gd and 154&155Eu, 192Ir, and 60Co) was achieved using a LN extraction resin in HCl media followed by further purification of Pm from 60Co and 192Ir using a low cross-linking cation exchange resin. Based on these data, we estimated that two rounds of purification under our experimental conditions can provide a mass separation factor of >104 between Pm and Nd. Our data indicate that curie quantities of 147Pm with suitable chemical and radioisotopic purity for applications in beta voltaic batteries can be produced by irradiating gram quantities of highly enriched 146Nd in the flux trap of HFIR for one cycle.
[en] Highlights: • Excitation functions of α-induced reaction on natZr up to 50 MeV were measured. • Production cross sections of Mo, Nb and Zr radioisotopes were determined. • End of bombardment activity of 99Mo was deduced. - Abstract: Cross sections of α-induced reactions on natural zirconium were measured up to 50 MeV using the stacked-foil technique, activation method and high resolution γ-ray spectrometry. The production cross sections of 93m,99Mo, 90g,92m,95g,95m,96Nb and 88,89g,95Zr were determined and compared with other experimental data measured earlier and result of theoretical calculations. The integral thick target yield of 99Mo was deduced from the measured cross section data.
[en] In this work we present an analysis of the dynamics of suprathermal ions of different masses (H, He, O) during prolonged dipolarizations in the near-Earth magnetotail (X > -17R/ according to Cluster/RAPID observations in 2001–2005. All dipolarizations from our database were associated with fast flow braking and consisted of multiple dipolarization fronts (DFs). We found statistically that fluxes of suprathermal ions started to increase 1 min before the dipolarization onset and continued to grow for 1 min after the onset. The start of flux growth coincided with the beginning of a decrease in the spectral index . The decrease in was observed for protons for 1 min after the dipolarization onset, and for He and O ions for 3 and 5 min after the onset respectively. The negative variations of for O ions were 2.5 times larger than for light ions. This demonstrates more efficient acceleration for heavy ions. The strong negative variations of were observed in finite energy ranges for all ion components. This indicates the possibility of nonadiabatic resonant acceleration of ions in the course of their interaction with multiple DFs during dipolarizations. Our analysis showed that some fraction of light ions can be accelerated up to energies 600 keV and some fraction of oxygen ions can be accelerated up to 1.2 MeV. Such strong energy gains cannot be explained by acceleration at a single propagating DF and suggest the possibility of multistage ion acceleration in the course of their interaction with multiple DFs during the prolonged dipolarizations.
[en] Most nuclear reactors under operation are thermal reactors, which consume U in once-through fuel cycle resulting in ineffective resource utilization and dramatic SNF volume growth. However, sustainable nuclear energy system (NES) should provide NFC closing for all hazardous radionuclides to minimize its life-time within NES and to make risk to be proportional to NES capacity, rather than total energy produced. These two basic principles require enough amount of neutrons for both energy generation and hazardous radionuclides transition to fission products. Therefore, taking into account politic, economic and technological risks and uncertainties, these issues can be solved in terms of two-component NES consisting of both thermal and fast reactors. In this work two methods to estimate neutron balance in NES are discussed. The fist method is based on the analysis of nuclear transformation chain due to radioactive decays and neutron induced reactions. The second one is the most complete one and relies on reaction rates comparison. Neutron balance estimation approach is demonstrated for two-component NES case study.
[en] A bright red luminescent composite material was prepared by combining a luminescent europium-based metal–organic framework (Eu-MOF) host with a red emitting sulfide (CaSrS:Cu,Eu). CaSrS:Cu,Eu particles were first prepared by calcination, and then these particles were used in a hydrothermal synthesis of Eu-MOF. By this approach, the CaSrS:Cu,Eu particles were naturally incorporated with the MOF. The luminescent properties indicated that the red emission intensity of the CaSrS:Cu,Eu@MOF product was much higher than that of the Eu-MOF itself due to the energy transfer from CaSrS:Cu,Eu to Eu-MOF. Furthermore, CaSrS:Cu,Eu@MOF displays enhanced emission intensity at the range of 400-500 nm and 600-700 nm, which are just the main absorption range for crops and plants. Thus, the prepared CaSrS:Cu,Eu@MOF was applied to prepared agricultural film. Results suggest that CaSrS:Cu,Eu@MOF could be a useful additive to polymer films for the agricultural sector.
[en] The properties of the quantum electrodynamic (QED) vacuum in general, and of the nuclear vacuum (ground) state in particular, are determined by virtual processes implying the excitation of a photon and of an electron-positron pair in the first case and of, for example, the excitation of a collective quadrupole surface vibration and a particle-hole pair in the nuclear case. Signals of these processes can be detected in the laboratory in terms of what can be considered a nuclear analogue of Hawking radiation. An analogy which extends to other physical processes involving QED vacuum fluctuations like the Lamb shift, pair creation by γ-rays, van der Waals forces and the Casimir effect, to the extent that one concentrates on the eventual outcome resulting by forcing a virtual process to become real, and not on the role of the black hole in defining the event horizon. In the nuclear case, the role of this event is taken over at a microscopic and fully quantum mechanical level, by nuclear probes (reactions) acting on virtual particles of the zero point fluctuations (ZPF) of the nuclear vacuum in a similar irreversible, no-return, fashion as the event horizon does, letting the other particle, entangled with the first one, escape to infinity, and eventually be detected. With this proviso in mind one can posit that the reactions H(Be,Be(2;3.37 MeV))H and H(Li,Li(1/2;2.69 MeV))H together with the associated γ-decay processes indicate a possible nuclear analogy of Hawking radiation.