The initial data for performing investigations directed toward elimination (transmutation) of radioactive wastes are the amount and composition of the long-lived nuclides contained in them. The results of a calculation of these characteristics depending on the scenario of development of nuclear power are presented in [1]. It is obvious that to determine the optimal transmutation, its efficiency in different types of nuclear plants, including both thermal and fast power reactors, must be compared already at the early stage of the investigations.Our objective in the present work is to compare the parameters characterizing the transmutation of Np, Am, and Cm in power reactors and the specialized subcritical plant UTA [2] with a high flux of thermal neutrons.As an example of the radiation hazard from long-lived nuclides (Np, AM, Cm, and Pu), in this work we investigate the concept of radiotoxicity (RMA, Rpu ) [1]. The values of RMA and Rr, u were determined according to their maximum admissible concentration (MAC) in water [3], taking account of the fact that in 1990 the ICRP changed the requirements --the MAC was decreased by a factor of I0 for plutonium, 2 for americium and curium, and 10 for neptunium [4].The model of continuous irradiation (transmutation) with a prescribed neutron flux was used for the computational investigations. This simplified model, which neglects the cyclic nature of the irradiation in solid-fuel reactors (UTA on liquid fuel can operate in a continuous mode), makes it possible to compare, by the simplest and clearest method, the results of transmutation in different setups.Two variants, concerning the quantity and composition of Np, Am, and Cm, which are used to replenish the setup in which transmutation is conducted (Table 1), were examined. I. Np, Am, and Cm extracted at a rate of 39.2 kg/(yr.GW) from spent fuel from thermal power reactors with uranium fuel for 1 GW of electrical power are transmuted. The holding time, from the moment the fuel is off-loaded to the start of irradiation, is 10 yr. 2. Np, Am, and Cm, extracted at a rate of 83 kg/(yr-GW) from spent fuel from thermal and fast power reactors (in equal ratio) with mixed fuel are transmuted. The holding period is 3 yr.If R i is the radiotoxicity of the i-th nuclide [1], then according to the data in Table I the total radiotoxicity of Np, Am, and Cm employed for replenishment is dRt/d~" = 1014 r-H20/O'r-GW) and dR2/d~" = 6
a b s t r a c tThe paper presents the measured cumulative yields of 44 Ti for nat Cr, 56 Fe, nat Ni and 93 Nb samples irradiated by protons at the energy range 0.04-2.6 GeV. The obtained excitation functions are compared with calculations of the well-known codes: ISABEL, Bertini, INCL4.2þABLA, INCL4.5þ ABLA07, PHITS, CASCADE07 and CEM03.02. The predictive power of these codes regarding the studied nuclides is analyzed.
Electronuclear plants have been under development without any visible success for many years. The main difficulties in this direction of development of nuclear power were associated with the high cost of the accelerator and the absence of a characteristic "niche" in the nuclear-power complex. In the last few years, however, the situation has largely changed --the safety standards for nuclear power plant operauon and burial of radioactive wastes have been made more stringent. It seems that the solution of these complicated problems, on which the future of nuclear power largely depends, can be found in the use of dual-purpose electronuclear plants within a nuclear-power complex for the production of electricity and for transmutation (annihilation) of long-lived radiotoxicity, determined mainly by Np, Am, and Cm produced in power reactors [1].In the present article, we present the results of conceptual investigations of a dual-purpose electronuclear plant operating on liquid fuel under the conditions of the uranium-plutonium fuel cycle.Let us examine in the equilibrium regime a dual-purpose electronuclear plant, whose blanket is f'dled with the working medium (liquid fuel) and is replenished with 238U (or natural uranium) and Np, Am, and Cm. Let ql and q2 be the specific rate of replenishment, which is constant in time, of the blanket with 238U and Np, Am, and Cm, respectively. Then the neutron multiplication factor in a homogeneous medium containing an equilibrium actinide density can be determined as follows:In Eq. (1) v t and Pl are, respectively, the number of neutrons produced and consumed in removing one 238U nucleus (actually, these quantities do not depend on the flux ~ of the thermal neutrons); ~' 2 and P2 are the analogous quantities for the annihilation of Np, Am, and Cm (the functions ~2(e,p) and p2(ecp) are defined in [2]); e is the relative time during which the working medium containing Np, Am, and Cm resides in the irradiation zone; E c is the macroscopic effective cross section for parasitic neutron capture in the fission products and in the medium (no actinides) f'dling the blanket; EF is the energy released in the fmsioning of one actinide nucleus; and, qv is the specific energy release in the working medium.Calculations of K~, using the formula (1) were performed for q, = 100 kW/liter, ql + q2 = 3.13"1012 nuclei/(cm3.sec) (-40 kg/(m3.yr)) and E c = 1.26-10 -4 cm -I, which corresponds to the absorption of thermal neutrons in I)20 with an admixture of 0. 1% light water and a low concentration of fission products, which are constantly removed from the medium in a special purification system [2]. The cross sections and resonance integrals were taken from [3]. Figures I and 2 display the functions K**(~) for e = 1 and 0.5 for different value of q2/ql. Essentially the same results are obtained when natural uranium is substituted for 238U.It follows from the calculations that for an equilibrium solution (suspension) of uranium and Np, Am, and Cm in heavy water with different values of q2/ql K~, <_ 1 (Ko...
The development of nuclear power production in the twenty-first century largely depends on the solution of problems of ecological acceptability of this method of energy production. The degree to which a nuclear power plant affects the environment is determined mainly by the radiotoxicity generated in power reactors. The formation of radiotoxieity depends strongly on the type of power reactor and the character of the fuel cycle. Therefore, it is of interest to analyze the accumulation of the long-lived radiotoxicity for different variants of the uranium-plutonium fuel cycle (open or closed) using thermal and fast power reactors.In the present paper we present the results of an analysis performed for the purpose of determining the initial data required to investigate the transmutation (elimination) of long-lived radiotoxicity of Pu, Np, Am, Cm, and fLssion products. The dissemination paths of such radiotoxicity, which determine its effect on the environment; have not been studied, with the exception of how the results are affected by the type of medium (water or air) into which radionuclides can enter in the course of different accidents as well as during long-time storage of radioactive wastes.The radiotoxicity was characterized by the concept of a specific index (STDi, which was determined by dividing I kg of a nuclide by the maximum admissable radioactivity of the same nuclide in 1 liter of water or air. Hence it follows that (STI) i determines the volume amount of water or air required to dilute 1 kg of the i-th nuclide to the maximum admissable concentration. This quantity makes it possible to compare different forms of radioactivity with a definite degree of objectivity. The values presented in Table 1 were calculated on the basis of the data of [1] taking into account the corrections introduced by the ICRP in 1990 [2]. In what follows we employ the values of (STI) i for water.Accum~d~tlon of Pu, Np, Am, and Cm radiotoxicity under the conditions of an open fuel cycle. In an open fuel cycle thermal reactors are the source of energy. For a systematic analysis we shall employ the characteristics of PWR power reactors with deep burnop of the fuel 33 MW-days/kg, which can be viewed as analogs of our own VVER-1000 reactors. The characteristics of PWR were determined according to the data of [3], The rate ql M~ at which Np, Am, and Cm enter long-term storage after a three-year holding period of the spent fuel, unloaded from a PWR with burnup of 33 MW-days/kg, and the analogous quantity ql pui for the i-th isotope of plutonium are presented in Table 2. Here and below, all data are presented for 1 GW of electrical power generated by nuclear power plants.During storage of spent fuel the isotopic composition of Pu, Np, Am, and Cm decreases as a result of decay of relatively short-lived nuclides. For example, in the case of storage for approximately 100 years almost all 2'upu decays into 241Am and 244Cm decays into 24~More than half of 238Pu decays into 234U and some 24lAin decays into 237Np. If a fuel assembly contains ...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.