Transmutation Of Isotopes Research Articles

Experience gained during 10 years transmutation experiments in Dubna

Transmutation, the procedure of transforming long-lived radioactive isotopes into stable or short-lived, was proposed for reducing the amount of radioactive waste resulting from technological applications of nuclear fission. The Accelerator Driven Systems (ADS) provide the possibility to generate intense neutron spectrum yielding in an effective transmutation of unwanted isotopes. Such experiments are being carried out for the last 10 years in Synchrophasotron / Nuclotron accelerators at the Veksler-Baldin Laboratory of High Energies of the Joint Institute for Nuclear Research in Dubna, Russia. Thick Pb and Pb-U targets, surrounded by moderators, have been irradiated by protons in the energy range of 0.5−7.4 GeV. Neutron fluence measurements have been performed by different techniques of passive detectors (neutron activation detectors, solid state nuclear track detectors). Transmutation of 129I, 237Np, 239Pu was studied. The results of these experiments are presented and discussed.

Transmutation: Towards Solving Problem of Spent Nuclear Fuel

An Accelerator Driven Subcritical System (ADS) is a promising, new concept for transmutation of long-lived isotopes originating from spent nuclear fuel. In the mainstream of research is the proton accelerator-driven ADS, however, on smaller scale an electron accelerator-driven machine could be an alternative. Using international codes we started to investigate the reactor physical aspects of such a device. In our paper we present the results of the first step of the modelling: the target optimization.

Transmutation of Long Lived Fission Products: The Possibilities of Proton Induced Reactions.

An option for management of nuclear spent fuel receiving more attention recently is transmutation of minor actinides and long lived fission products (LLFP’s) into stable or shorter lived isotopes. Different authors state that if a solution for the transmutation of the MA was found the greatest overall remaining risk to health may come from LLFP’s as 126Sn, 79Se , 93Zr, 99Tc, l29I and 135Cs. The few references to transmutation of LLFP’s assume that (n, γ) reactions are used for incineration in dedicated ADS systems.We show that charged particle induced reactions on LLFP, especially the (p,n) reaction, also mostly result in formation of either short lived, either stable isotopes. As for both cases transmutation of isotopes, initially not relevant isotopes for waste management, could result in the production of new long lived products, elemental partitioning is necessary. We list and discuss the results for (n,γ) and (p,n), reactions in terms of transmutation products obtained on stable fission products and on the critical LLFP’s mentioned above.Transmutation rates and obtainable loads, with comparisons and numerical values for some cases are presented. Realisation of charged particle irradiation, economics and public acceptance are discussed.

Transmutation of commercial waste should precede geological storage.

Technology has provided solutions for many of our problems. The generation and distribution of electricity to our homes and businesses has made possible our comfortable modern lifestyle. Of course, nothing comes without a price, and one of the prices we pay for our electrically powered world is the difficulty of managing the wastes resulting from power production. The basic methods used to deal with many types of waste are generally rather primitive. Waste products may be diluted, dispersed or buried in approved places. Rather few waste products resulting from the production of electric power are biodegradable. However, when it comes to nuclear waste, transmutation may offer a solution to a problem that has existed in many countries for many years, if it proves to be technologically and economically feasible. Recently, there have been severe electric power problems in the US. These problems have stimulated renewed interest in developing additional sources of power, with nuclear power being one of those sources. The prospect of increasing the number of nuclear power reactors, while the US capabilities for long-term geological storage of spent fuel are still unclear, is daunting. Transmutation of long-lived isotopes in spent fuel to shorter-lived or more benign isotopes may be necessary, if the process can be performed economically.

Conditions of transmutation of plutonium, americium, and curium in nuclear facilities

The transmutation of plutonium, americium, and curium isotopes in reactors with thermal and fast neutron spectra is analyzed. The radiotoxicity of a nuclide mixture is calculated. For transmutation of plutonium the radiotoxicity is maximum at the initial stage of irradiation as a result of the production of 241Pu and, after further irradiation, the production of 244Cm. For transmutation of americium and curium the maximum radiotoxicity is 2–2.5 times greater than the initial value; it is due to the formation of 238Pu. It is established that the neutron flux density affects the rate of decrease of radiotoxicity. 5 tables, 5 references.

Actinide transmutation: new investigation on some actinide compounds

Mixtures of actinide oxides with other oxides have been studied for transmutation of long-lived isotopes in nuclear power reactors and for optimization of plutonium consumption in fuels. These materials are solid solutions or composites selected with criteria used for classical fuels, and pellets with uranium, neptunium or plutonium have been prepared and characterized. The actinide phases analyzed in composites with magnesia are not fully compatible with the phase diagrams previously published. The results of specific heat measured on (Y,U)O 2+ x solid solution show a deviation from Kopp's law, and the effect of substitution of multivalent actinides by trivalent ions is discussed. Irradiation damage produced by fission products have been studied by simulation with ion irradiation. The good behavior of the actinide compounds with magnesium oxide, and the favorable effect of addition of actinide oxide in inert matrices had been observed.

Deep levels of chromium in 4H-SiC

Deep levels of transition metals in 4H-SiC were investigated. A definite chemical identification is achieved by observing the elemental transmutation of radioactive isotopes. Epitaxial layers of n-type 4H-SiC were doped with the radioactive isotopes 48V and 51Cr by recoil implantation and subsequent furnace annealing at 1600 K. Repeated deep level transient spectroscopy (DLTS) measurements were performed during the elemental transmutation of these isotopes to 48Ti and 51V, respectively. In the case of 51Cr, three levels at 0.74, 0.18 and 0.15 eV below E C disappear with a time dependence of the nuclear decay, i.e. these levels are due to chromium. In the case of the 48V implantation, there is a comparatively strong tendency to form a compensated layer under identical implantation and annealing conditions. A level at E C — 0.97 eV is identified with vanadium in 4H SiC.

Conceptual design of a fusion engineering test facility based on mirror confinement (FEF)

The results are presented from the feasibility study on a fusion engineering test facility based on mirror confinement (FEF) and are intended to clarify the critical issues both in the physics and engineering. The objectives of FEF are (i) to test many fusion engineering components associated with 14 MeV neutrons, such as material tests, tritium test, thermo-hydraulic test as well as the interactive and integrated tests, and (ii) to study the useful applications of fusion produced neutrons for other purposes, such as fission fuel production, radio isotope production and transmutation of nuclear waste. The design philosophy of the FEF is to build a compact and linear fusion plasma neutron source in an axisymmetric magnetic field configuration which could be built in near future. The characteristics of FEF are (i) usage of radio frequency power for heating and stabilization of the MHD mode of the plasma, (ii) usage of water for the shielding of the device, and (iii) usage of a direct energy conversion system for the end region of the mirror plasma. The basic specifications of FEF as the irradiation facility are: 14 MeV neutron wall leading of 1–2 MW/m 2 , and irradiation area of 1 m 2 . The major critical issues which are found through this work are: (i) the physics aspects, needs of the data bases for RF ponderomotive stabilization of the MHD mode and for pellet injection and (ii) the engineering issues, bombardment of high energy particles on the rf antenna and on the vacuum chamber and damage of the insulators.

The French Liquid-Metal Fast Breeder Reactor Program

In any operating nuclear reactor, new fissile isotopes are formed by transmutation of fertile isotopes even as fissile isotopes are consumed. In slow-neutron, or ''thermal'' reactors, which are the backbone of nuclear programs throughout the world today, more fissile isotopes are consumed than are reproduced. The fuel therefore rapidly loses its usefulness and must be removed, even though it contains a substantial portion of untransformed fertile isotopes. Fast-neutron reactors, however, have a neutron balance that is particularly conducive to greater production than consumption of fissile isotopes. This is the so-called ''breeding'' phenomenon. This property, while remarkable, is by no means miraculous. It is simply the consequence of the numerical values of the nuclear properties of heavy nuclides; this has been known since the earliest fission experiments. What gives the breeding phenomenon such appeal today is that the reactors that use it can make a crucial contribution to the problem of world energy supply in the long term. The preceding considerations provide a glimpse of the fast-neutron reactor's attractiveness in long-term energy planning for a country like France, one of the most industrialized countries in the world yet one of the poorest in fossil resources. This theme is developed first bymore » demonstrating that breeder reactors can make an essential contribution to France's energy independence, then by describing the country's technical experience and the industrial organization it has implemented in this area, and finally by discussing the difficulties that remain to be resolved and the future prospects for this type of reactor in France.« less

Fission Product Model for BWR Lattice Calculation Code

A benchmark calculation of full fission product was performed for thermal reactor application using an isotope transmutation code DCHAIN based on 185 nuclides with revised nuclear data library. The fission product model for BWR lattice calculation was studied and tested with the benchmark results, and a model containing 45 explicit nuclides and one pseudo nuclide was selected as a reasonably best model to predict the burn up reactivity with high precision for practically all types of fuel and reactor operating conditions. The evaluated thermal cross section and resonance integral for the pseudo nuclide are σ2,200 = 2.6b and.RI = 10.6b, combined with the pseudo fission yield values of 1.3898, 1.3233, 1.3675 and 1.2773 for fissions from 235U, 238U, 239Pu and 241Pu, respectively. The present results are believed as equally applicable to PWR lattice calculation.

The possibility of isotope transmutation alloying

The possibility of isotope transmutation alloying