Fission product groups

The results of the Level 2 PSA are usually presented in the form of a table of source term categories or release categories together with their frequencies of occurrence. The source term and/or release categories are defined in terms of their composition of radionuclides (grouped into fission product groups in accordance with... 

During the operation of nuclear power reactors, which are fuelled with ceramic UO2 fuel rods, the fission of the nuclei leads to die formation of fission products which are isotopes of elements in all of tire Groups of the Periodic Table. The major fission products, present in 1-10% abundance, fall into five groups divided according to the chemical interaction of each product with the fuel ... 

Stanley G. Thompson joined my group on October 1, 1942 and it fell to his lot to discover the process that was chosen for use at Clinton Laboratories (in Tennessee) and the Hanford Engineer Works (in the state of Washington) for the separation of plutonium from uranium and the immense intensity of radioactive fission products with which it was produced in the nuclear chain reactors. Again I turn to my journal to tell the story ... 

We have studied the extractant behavior of a series of compounds containing the carbamoylmethylphosphoryl (CMP) moiety in which the basicity of the phosphoryl group and the steric bulk of the substituent group are varied (10,LL). These studies have led to the development of extractants which have combinations of substituent groups that impart to the resultant molecule improved ability to extract Am(III) from nitric acid and to withstand hydrolytic degradation. At the same time good selectivity of actinides over most fission products and favorable solubility properties on actinide loading are maintained (11). 

The final answer came from the atomic pile. J. A. Marinsky, L. E. Glendenin, and C. D. Coryell at the Clinton Laboratories at Oak Ridge (20) obtained a mixture of fission products of uranium which contained isotopes of yttrium and the entire group of rare earths from lanthanum through europium. Using a method of ion-exchange on Amberlite resin worked out by E. R. Tompkins, J. X. Khym, and W. E. Cohn (21) they were able to obtain a mixture of praseodymium, neodymium, and element 61, and to separate the latter by fractional elution from the Amberlite column with 5 per cent ammonium citrate at pH 2.75. Neutron irradiation of neodymium also produced 61. 

Cd azides, Ag acetylide and nitrogen iodide) by electrons, neutrons, fusion products and X-rays. All these substances were exploded by an intense electron stream but it was shown that this was due to a thermal effect. Fission products exploded nitrogen iodide but in the other substances some changes within the crystals took place but no explosions. The experiments showed that, in general, the activation of a small group of adjacent molecules was not enough to cause explosion... 

In following sections, the selected key recent results from our research group on the separation of fission products (Sr + and Cs ) are outlined. For readers who are interested in IL-based extraction systems for ofher metal ions, several excellent reviews are very helpful. Rogers and coworkers [44] have written an excellent review on use of ILs for extraction of lanfhanides and actinides. 

In this chapter, we provide an overview of our recent research on solvent extraction of fission products based on ILs. Since the inception of fhe IL-based extraction system for metal ions in 1999, this approach has proven to be highly efficient for the extraction of metal ions. The success of the IL-based extraction systems lies in its ionicity, tunability, ion exchangeability, and nonvolatility. Although this review is focused on the recent research activities of our research groups, we hope to convince readers that the separation of metal ions based on IL is a fascinating research arena. Existing achievements and many anticipated future advances in this area will have fundamental and practical impacts on separation sciences. 

Liquid HLW from reprocessing of SNF may consist of 50-60 elements, including about 90 radionuclides of 35 chemical elements of fission products (FP) and more than 120 radionuclides due to FP decay. The total activity of HLW may achieve 1016 Bq/m3 (Nikiforov el al. 1985). The HLW elements can be divided into four groups ... 

In parametric studies using this method, calculation of fission product distribution among the various particle size groups was found to be insensitive to size of the detonation and the quantity of soil picked up. It is, of course, somewhat sensitive to the thermodynamic and kinetic values used, but most of all, it is sensitive to the particle size distribution itself. This result is of considerable interest. 

There are little data available which can be used to predict the rates of uptake of the different vaporized radioactive elements or oxides. Since such data are important to the application of any fallout prediction model based on kinetics, a program has been started at this laboratory to measure the rates of uptake of a selected group of fission-product oxides under conditions approximating those found in the cooling fireball. The data from these measurements will be useful, not only as input to fallout models, but also for discovering the mechanisms which govern the rates of uptake. 

The third principal component of environmental radioactivity is that due to the activities of humans, the anthropogenic radionuclides. This group of nuclides includes the previously discussed cases of 3H and 14C along with the fission products and the transuranium elements. The primary sources of these nuclides are nuclear weapons tests and nuclear power plant accidents. These events and the gross nuclide releases associated with them are shown in Table 3.1. Except for 14C and... 

In the chemistry of the fuel cycle and reactor operations, one must deal with the chemical properties of the actinide elements, particularly uranium and plutonium and those of the fission products. In this section, we focus on the fission products and then chemistry. In Figures 16.2 and 16.3, we show the chemical composition and associated fission product activities in irradiated fuel. The fission products include the elements from zinc to dysprosium, with all periodic table groups being represented. 

Studies of the effect of neutron irradiation are divided into three groups slow or thermal neutrons, fission products and reactor neutrons. The slow neutrons are obtained from a radioactive source or high energy neutrons that are produced by deuterium bombardment of a beryllium target in a cyclotron and slowed down passing thru a thick paraffin wax block. The fission products in one case are produced when a desired sample is mixed or coated with uranium oxide and subsequently irradiated with slow neutrons. The capture of neutrons by U23S leads... 

Before the development and widespread application of spectroscopic methods for the elucidation of structure, confirmation of the class type of an unknown organic compound was completed by the preparation of two or more crystalline functional derivatives. If the compounds had been previously reported in the literature, agreement between the published physical constants of the derivatives with those prepared by the worker was accepted as proof of identity. In many cases, and particularly in natural product chemistry, functional group recognition led to oxidative, reductive, or hydrolytic breakdown into smaller carbon-containing fragments. These were, if necessary, separated, characterised and identified by derivative preparation. The reassembly of the jig-saw of fragments inferred by the identity of the fission products, then led to postulated structures. 

A mixture of well-known extractants, di-(2-ethylhexyl)phosphoric acid (HDEHP) and CMPO, in n-paraffin was used for the study of combined extraction of different actinides (americium, plutonium, and uranium) and lanthanides (cerium and europium) and their separation from fission products (cesium, strontium, ruthenium, and zirconium).54 Combined extraction of MAs and lanthanides was studied together with group separation of MAs from lanthanides by selective stripping with a solution of diethylenetriaminepentaacetic acid (DTPA), formic acid, and hydrazine hydrate. This solution strips only MAs, leaving lanthanides in the organic phase. Subsequently, the lanthanides are stripped using a mixture of DTPA and sodium carbonate. 

This review groups the information published on degradation of the main families of extractants studied in the frame of long-lived minor-actinide and fission-product recovery (1-4) (see Chapter 1) alkyl-phosphorus compounds (phosphates, phosphonic acids, bifunctional compounds like CMPO), amide compounds (dialkyl-amides, malonamides, and diglycolamides), N-donor compounds, and macrocycles like crown ethers and calixarenes (Table 8.1). The multicomponent systems based on the chlorinated cobalt dicarbollide process have not been considered. 

---