Mixture Of Fission Products Research Articles

Ion exchange chromatography on a new form of tin dioxide for the isolation of strontium radioisotopes from fission products: an application to milk samples

An amorphous, partially-reduced tin dioxide, having properties of an inorganic exchanger, was tested for application to fission product separations. Due to the good sorption of both strontium and barium the application of the exchanger to radiostrontium isolation from fission product mixtures is subject to important restrictions. An application to 90Sr determination in milk is proposed.

Levels in 109Rh

The levels in 109Rh have been investigated via the γ-rays following the β− decay of 34.5 s 109Ru. The ruthenium activity was produced in the thermal neutron-induced fission of 149Cf and separated chemically from the fission product mixture with the on-line centrifuge system SISAK. The emitted γ-rays were studied by γ singles and γγ(t) coincidence measurements. In addition, the 110Pd(d, 3He) reaction was investigated at Ed = 50 MeV to study the proton-hole states in 109Rh. From the comparison of the measured angular distributions with DWBA calculations l-transfers and spectroscopic factors were deduced. The level scheme of 109Rh that was obtained is discussed and compared with neighbouring nuclei and with recent calculations in the framework of the interacting bosonfermion model (IBFM-1). An interpretation of the observed candidates for intruder states as a rotational band built upon the [431] Nilsson configuration is proposed.

Levels in 107Rh

The levels in 107Rh have been investigated via the γ-rays following the β − decay of 3.75 min 107Ru. The ruthenium activity was produced in the thermal neutron-induced fission of 239Pu and separated chemically from the fission product mixture with the on-line centrifuge system SISAK. The emitted γ-rays were studied by γ singles and γγ( t) coincidence measurements. In addition, the 108Pd(d, 3He) reaction was investigated at E d = 50 MeV to study the proton-hole states in 107Rh. From the comparison of the measured angular distributions with DWBA calculations l-transfers and spectroscopic factors were deduced. The obtained level scheme of 107Rh is discussed and compared with neighbouring nuclei and with recent calculations in the framework of the interacting boson-fermion (IBFM-1) model.

Volatility of fission products during reactor accidents

This paper summarizes some current generic work on the behaviour of iodine, cesium, and tellurium under conditions expected to occur during postulated reactor accidents. We discuss Knudsen cell experiments to elucidate the high-temperature properties of fission-product mixtures, steam-flashing experiments to measure iodine transfer to the gas phase, and the formation and volatility of organic iodides in aqueous solutions.

Effect of the (n, ?) reaction on the radiative characteristics of a mixture of fission products

Effect of the (n, ?) reaction on the radiative characteristics of a mixture of fission products

Rapid continuous separation procedures for zirconium, niobium, technetium, bromine and iodine from complex reaction product mixtures

Fast, continuous methods for the separation of radiochemically pure samples of Zr, Nb, Tc, Br and I from fission product mixtures are described. The procedures involve multistage solvent extraction separations with the centrifuge facility “SISAK 2” connected to a gas-jet recoil transport system. The mean transport time between production and measurement amounts to 5–9 s depending on the element to be separated.

Decay of 85–88Se to levels in 85–88Br

The ß −-decay of the neutron-rich nuclides 85Se 88Se has been investigated by γ-ray singles and coincidence measurements. The activities have been produced by thermal-neutron induced fission of 235U with subsequent chemical separation of the selenium fraction from the fission product mixture using an on-line gas phase procedure. A revised decay scheme for 85Se and partial decay schemes for 86–88Se are proposed.

Separation and purification of radiomolybdenum from a fission product mixture using silver-coated carbon granules

A highly specific 99Mo separation and purification procedure has been developed which utilizes silver-coated-charcoal (Ag-C) as the adsorbent. The Ag-C is prepared by contacting a silver nitrate solution with charcoal granules and then reducing the silver with sodium sulfite. This resin system selectively and quantitatively adsorbs molybdenum from a dilute H 2SO 4-fission product solution. Greater than 80% of the adsorbed 90Mo can be recovered from the adsorbent in a dilute NaOH eluant. The purity of the 99Mo solution from a single adsorption-desorption process is greater than 99%.

The decay of 79.8 sec 109Rh into levels of 109Pd

The β −-decay of 79.8 sec 109Rh into levels of 109Pd has been investigated by γ-ray spectroscopy and γ-γ-coincidence measurements. The activities have been produced by thermal-neutron induced fission of 239Pu and subsequent chemical separation of the rhodium fraction from the fission product mixture. A total of 31 γ-rays have been assigned to the decay of 109Rh, and a level scheme of 109Pd is proposed and briefly discussed within the framework of different nuclear models. From beta branching ratios a groundstate spin and parity of 5 2 + can be deduced for 109Rh.

Identification of short-lived ruthenium and rhodium isotopes in fission by rapid chemical separations

Short-lived ruthenium and rhodium isotopes were produced via thermal neutron induced fission of 235U, 239Pu and 249Cf and via fast neutron induced fission of 238U. The ruthenium isotopes and their descendants were isolated from the fission product mixtures by means of a rapid chemical separation procedure. Typically 7.6 sec were required from the end of irradiation to the start of counting. The γ-ray singles spectra as well as the γ-γ-coincidences were recorded with Ge(Li)-detectors. New short-lived nuclides were identified on the basis of their decay characteristics, and existing data of the longer lived isotopes were confirmed. Results are presented for the ruthenium isotopes 3.75 min 107Ru, 4.55 min 108Ru, 34.5 sec 109Ru, 12.9 sec 109Ru (isomer), 12.6 sec 110Ru, 3 sec 111Ru, 3.6 sec 112Ru, 3 sec 113Ru, and the rhodium isotopes 17 sec 108Rh, 79.8 sec 109Rh, 3.3 sec 110Rh, 11 sec 111Rh.

High-Level Waste Glass

Glass is a good material in which to incorporate high-level radioactive waste (HLW) for permanent storage. HLW, a complex mixture of fission products and actinides, results from the reprocessing of spent power reactor fuel elements to reclaim uranium and plutonium. Processes for making low-temperature waste glasses (1050°C processing temperature) have been developed to the stage that they can be utilized in commercial reprocessing plants in the early 1980’s. A representative low-melting waste glass formulation has been shown, in accelerated tests, to possess satisfactory thermal and radiation stability for many centuries of storage, and indications are that this stability will be maintained for longer times. The waste glass can be melted and stored in Type 304L stainless-steel canisters, although investigations of metals that may have increased high-temperature strength is continuing. A ceramic melting process that will permit manufacture of higher melting HLW glass, if this proves desirable, is also being developed.

Methods of Adjustment and Error Evaluation of Neutron Capture Cross Sections; Application to Fission Product Nuclides

In the analysis of fission product reactivity worths, measured in the fast reactor spectra of the STEK critical-experiments facility, extensive use is made of a statistical method of cross section adjustment. The principle is that adjustments are applied to the evaluated cross sections, as much as possible within their error limits and taking into account the existing correlations, in such a way that a better agreement between calculated and measured integral data is obtained. The method is briefly summarized in general terms, with some special applications needed for the STEK project. Then, a description is given of the practical realization for capture cross-section adjustment on the basis of reactivity worths of samples of fission product mixtures in different thicknesses measured in several fast reactor spectra. Details are given on the way the various contributions to the covariance matrix of group cross sections, including resonance self-shielding, are calculated for the fission product nuclides and for the mixtures. The paper outlines the methods used. Some limitations of the method and possible extensions in connection with standard nuclear data error files are discussed.

Decay properties of neutron-rich niobium isotopes

The decay of neutron-rich niobium isotopes in the mass region $A\ensuremath{\simeq}100$ has been investigated by $\ensuremath{\gamma}$-ray singles and $\ensuremath{\gamma}$-$\ensuremath{\gamma}$ coincidence measurements. The isotopes were produced by thermal-neutron induced fission of $^{235}\mathrm{U}$, $^{239}\mathrm{Pu}$, and $^{249}\mathrm{Cf}$, and niobium was separated from fission-product mixtures with an automated chemical procedure. Isomerism was found in the even-mass niobium isotopes with the following half-lives: 1.5 and 3.1 sec for $^{100}\mathrm{Nb}$, 1.3 and 4.3 sec for $^{102}\mathrm{Nb}$, and 0.8 and 4.8 sec for $^{104}\mathrm{Nb}$. Half-lives and $\ensuremath{\gamma}$ rays were assigned to the 15.0-sec $^{99}\mathrm{Nb}$, 7.1-sec $^{101}\mathrm{Nb}$, 1.5-sec $^{103}\mathrm{Nb}$, and \ensuremath{\sim}1-sec $^{106}\mathrm{Nb}$. Revised half-life values are given for the 7.1-sec $^{100}\mathrm{Zr}$ and 2.9-sec $^{102}\mathrm{Zr}$. RADIOACTIVITY $^{99,100,101,102,103,104,106}\mathrm{Nb}$, $^{100,102}\mathrm{Zr}$; measured ${T}_{\frac{1}{2}}$, ${E}_{\ensuremath{\gamma}}$, $\ensuremath{\gamma}$-$\ensuremath{\gamma}$-coin. $^{100,102,104}\mathrm{Mo}$ deduced levels. Fission $^{235}\mathrm{U}$, $^{239}\mathrm{Pu}$, $^{249}\mathrm{Cf}({n}_{\mathrm{th}},f)$; automated chemical separation procedure, Ge(Li) detectors.

Identification ofTc109andTc110in fission ofCf249

The neutron-rich nuclides $^{109}\mathrm{Tc}$ and $^{110}\mathrm{Tc}$, produced by thermal-neutron-induced fission of $^{249}\mathrm{Cf}$, have been identified using a fast automated chemical procedure for the separation of technetium from the fission product mixture. Half-lives of 1.4\ifmmode\pm\else\textpm\fi{}0.4 and 1.0\ifmmode\pm\else\textpm\fi{}0.2 sec for $^{109}\mathrm{Tc}$ and $^{110}\mathrm{Tc}$, respectively, have been deduced from $\ensuremath{\gamma}$-ray spectra of the technetium fraction.RADIOACTIVITY $^{109}\mathrm{Tc}$, $^{110}\mathrm{Tc}$, measured ${T}_{\frac{1}{2}}$. Fission $^{249}\mathrm{Cf} ({n}_{\mathrm{th}},f)$; automated chemical separation procedure, Ge(Li) detector.

Gamma-ray emission from 80–86As isotopes

Activities of 80–86As were produced in (n, p) reactions on stable selenium nuclei, as fission products, and via β− decay from their germanium precursors. To separate arsenic and germanium from fission product mixtures, rapid chemical separations were applied. Gamma-ray emission from arsenic isotopes was studied in γ-single and γγ coincidence experiments. Partial decay schemes are proposed for 34 sec 81As, 14.0 sec and 19.1 sec 82As, 13.3 sec 83As, and 5.3 sec 84As. The delayed-neutron branch in the decay of 2.05 sec 85As was shown to preferentially populate several excited levels in 84Se while the ground state of 84Se is fed to 29 % only. The systematics of low-lying levels in doubly even selenium isotopes is extended up to mass number 86. Discontinuities in the systematics at N = 48 are interpreted as an indication of a soft character of the nucleus 82Se.

Thermal degradation of 2-deoxy- D- arabino-hexonic acid and 3-deoxy- D- ribo-hexono-1,4-lactone

Heating of 2-deoxy- D- arabino-hexonic acid results in substantial lactonization on melting. Decomposition of the lactone involves dehydration, decarboxylation, and fission to provide mainly water, 5-(2-hydroxycthylidene)-2( 5H)-furanone, carbondioxide, carbon monoxide, acrylaldehyde, and acetic acid. 3-Deoxy- D- ribo-hexono-1,4-lactone, which could not readily undergo β-elimination, is thermally more stable and gives a mixture of fission and dehydration products.

The decay of105Tc to levels in105Ru

Theβ−-decay of 7.6-min105Tc has been investigated byβ- andγ-ray singles and coincidence measurements. The activities have been produced by thermal-neutron-induced fission of235U or239Pu and subsequent chemical separation of the technetium fraction from the fission product mixture. AQβ-value of 3.2±0.2 MeV has been determined. In a delayed coincidence experiment the lifetime of the first excited state in105Ru at 20.55 keV has been measured to be 340±15 nsec. A level scheme of105Ru is proposed and compared with the results of recent nuclear reaction studies like104Ru(d, p) and104Ru(n, γ). From beta branching ratios to levels in105Ru, ground state spin and parity of 5/2+ can be suggested for105Tc in accordance with the trend observed in neutron rich technetium isotopes.

Gamma-ray emission from 84–87Se and 85–88Br isotopes

Abstract Gamma-ray emission from 84 Se, 85 Se, 86 Se, 87 Se, 85 Br, 86 Br, 87 Br and 88 Br has been studied over the energy range 300–7100 keV using a Ge(Li) detector. Selenium isotopes were separated from a mixture of fission products using high-speed radiochemistry and the bromine daughters allowed to grow in. The large difference in half-life between 86 Se and 87 Se was used to distinguish between 86 Br (54 sec) and 87 Br (55 sec). New gamma lines have been assigned to selenium isotopes as follows: a line at 498·5 ± 0·6 keV to 84 Se; thirty-seven lines to 85 Se; seven lines to 86 Se; two lines to 87 Se. At least 98 per cent of decay of 84 Se is found to go via the ground state of 84 Br (31·7 min). A partial decay scheme is proposed for 85 Se. The half-lives of 85 Se and 86 Se were found to be 31·4 ± 1·0 sec and 14·4 ± 1·0 sec, respectively. A line at 832 keV previously assigned to 85 Br has been shown to be due to 90m Rb + 90 Rb. Data for 86 Br are generally in agreement with previous findings but three new lines were observed at 6161·5 ± 2·0, 6722 ± 3 and 6768·3 ± 1·5 keV, which must represent new levels in 86 Kr. Only the strongest lines were observed in the decay of 87 Br and 88 Br and these are generally in agreement with previous work.

The gas-jet recoil transport method as part of a system for rapid aqueous radiochemical separations

The gas-jet recoil transport method has been adapted for the use as part of a system for rapid radiochemical separations. The recoil atoms are transported directly into a liquid chemical system with which subsequent chemical separations are carried out. Calculations show that the collector chamber can be operated at atmospheric pressure to allow easy performance of the chemistry without increasing severely the overall transport time. Transport efficiencies of 15–20% for fission products have been achieved. Application of the method is illustrated by radiochemical separations of Ba fission products from the fission-product mixture obtained by using a Ba carrier solution in HNO 3 as catcher.

Online Monitoring of Specific Radionuclides in Gaseous Effluents

A feasibility study of automatic online monitoring of specific radionuclides in nuclear plant gaseous effluents is being conducted at the Georgia Tech Research Reactor (GTRR). An inpile loop experiment has been designed, built, and operated in the GTRR to simulate gaseous effluent mixtures anticipated for a variety of reactor situations. The gaseous fission product mixture may be altered by varying the flow rate of the helium sweep gas over the uranium-235 loaded microporous target, the neutron flux and temperature at the target, and the configuration of the cryogenic trapping system external to the reactor. The loop is used for experiments in remote monitoring of specific radionuclides to be experienced for normal, minor malfunction, and accident conditions at a nuclear plant. As a means of evaluating the practical aspects of automatic online monitoring, a remote monitoring system has been designed and built to measure nuclear and meteorological data at the GTRR, and to transmit the data to a central computer on either a routine "record keeping" or on an emergency-interrupt basis. The measurement system can be adjusted from the remote location to allow live time probing of conditions at the monitored location.