A total absorption γ-ray spectrometer (TAGS), based on a 25.4 cm diameter × 30.5 cm long NaI(Tl) well detector, has been developed at the INEL on-line isotope separator facility. A Si detector in the well of the NaI(Tl) detector allows one to collect β-particle-gated coincidence spectra as well as singles spectra. With this system, measurements of the total absorption spectra have been made for a number of fission product nuclei. The analysis of the measured spectra is based on response functions for single γ rays that are computed with a Monte Carlo code. Routines have been written to use these response functions to simulate the response to a cascade of several γ rays and by extension to a whole decay scheme. The bremsstrahlung from a ground-state β branch can also be simulated. The quality of the simulation is demonstrated for test spectra of 137Cs, 24Na, 60Co, and 110mAg. As examples of the operation of this system, the measurements and analyses of the β-decay feeding distributions are described for the decay of 141Ba, 139Cs and 140Cs.

A method has been developed to measure ground-state beta--branching intensities with the total absorption gamma-ray spectrometer at the INEL ISOL facility. This spectrometer, which is used to measure beta-feeding (or beta-strength) distributions to excited states in neutron-rich fission-product nuclei, consists of a 25.4 cm diameter x 30.5 cm long well-type NaI(Tl) scintillation detector together with a Si beta- detector located in the collection-tape transport line in the well. With this spectrometer operating in the beta-gamma coincidence mode as a 4-pi-gamma-beta detector, ground-state beta--branching intensities are obtained from simple ratios of beta-gamma coincidence to beta-singles count rates together with additional, generally small, correction terms. Results obtained for Rh-106, Cs-138-141, Ba-141-142, La-142-145 and Ce-145 are presented and compared with existing data obtained with conventional nuclear spectroscopic methods.

A method has been developed to measure ground-state β−-branching intensities with the total absorption γ-ray spectrometer at the INEL ISOL facility. This spectrometer, which is used to measure β-feeding (or β-strength) distributions to excited states in neutron-rich fission-product nuclei, consists of a 25.4 cm diameter × 30.5 cm long well-type NaI(Tl) scintillation detector together with a Si β− detector located in the collection-tape transport line in the well. With this spectrometer operating in the β-γ coincidence mode as a 4πγ−β detector, ground-state β−-branching intensities are obtained from simple ratios of β−γ coincidence to β singles count rates together with additional, generally small, correction terms. Results obtained for 106Rh, 138–141Cs, 141–142Ba, 142–145La and 145Ce are presented and compared with existing data obtained with conventional nuclear spectroscopic methods.

In recent years, the use of the mass separation technique coupled on-line to a source of fission product nuclides has provided a wealth of new information on the nuclear decay properties of such nuclides. In addition to their relevance in basic studies of nuclear properties of neutron-rich nuclei, the fission product nuclides as a group, because of their intimate link with energy production in fission reactors, occupy a unique position in the field of applied nuclear decay data. Further, in addition to their critical role in nuclear reactor technology (decay heat source term, environmental concerns, etc.), such data have important applications in astrophysical calculations involving the rapid neutron capture process (r-process) of elemental synthesis in stellar environments. The scope of the nuclear decay data measurements being undertaken using the Idaho National Engineering Laboratory's (INEL) isotope separation on-line (ISOL) facility is focused on a systematic study of the gross nuclear decay properties of short-lived fission product isotopes, i.e., ground-state half-lives, beta-decay energies and beta-decay feeding (or beta-strength) distributions. In this paper, the authors discuss the results of new measurements of beta-decay energies and feeding distributions.

Permeation and reemission of deuterium for the vanadium alloy, V-15Cr-5Ti, was investigated using 3 keV, D3+ ion beams from a small accelerator. The experiments consisted of measurement of the deuterium reemission and permeation rates as a function of implantation fluence for 0.5 mm thick specimens heated to temperatures from 623 K to 823 K. Implantation-side surface characterization was made by simultaneous measurements of sputtered ions with a secondary ion mass spectrometer (SIMS). For the experimental conditions used, the steady-state deuterium permeation flux in V-15Cr-5Ti is approximately 18% of the implantation flux. This is approximately 1000 times that seen in the austenitic stainless steel, PCA, and 200 times that seen in the ferritic steel, HT-9, under comparable conditions. Measurement of deuterium diffusivity in V-15Cr-5Ti using permeation break-through times indicates that D = 1.4 × 10−8 exp( −0.11 eV/kT) (m2/s), over the temperature range 723 K to 823 K.

This paper describes a data acquisition system developed for hydrogen ion-driven permeation experiments for materials relevant to fusion technology. The system consists of an IBM PC-AT, CAMAC interface to diagnostic instrumentation and custom-developed software (BASIC) to provide time-history information for signals from several instruments including three quadrupole mass spectrometers.

Permeation of deuterium through the vanadium alloy, V-15Cr-5Ti, was investigated using 3-keV, D/sub 3//sup +/ ion beams from a small accelerator. The experiments consisted of measurements of the deuterium reemission and permeation rates as a function of implantation fluence for 0.5-mm thick specimens heated to tempertures from 623 to 823/sup 0/K. Implantation-side surface characterization was made by simultaneous measurements of sputtered ions with a secondary ion mass spectrometer (SIMS). Analyses of these measurements indicate that for the experimental conditions used, the steady-state deuterium permeation flux in V-15Cr-5Ti is approximately 18% of the implantation flux. This corresponds to approximately 1000 times that seen in the ferritic steel, HT-9, under comparable conditions. Measurement of deuterium diffusivity in V-15Cr-5Ti using permeation break-through times indicates D = 1.4 x 10/sup -8/ exp(-.11 eV/kT) (m/sup 2//s).

Implantation-driven permeation experiments have been conducted on samples of the ferritic steel HT-9, the austenitic Primary Candidate Alloy (PCA) and the vanadium alloy V-15Cr-5Ti using D3+ ions under conditions that simulate charge-exchange neutral loading on a fusion reactor first wall. The steels all exhibited an initially intense permeation "spike" followed by an exponential decrease to low steady-state values. That spike was not evident in the V-15Cr-5Ti experiments. Steady-state permeation was highest in the vanadium alloy and lowest in the austenitic steel. Though permeation rates in the HT-9 were lower than those in V-15Cr-5Ti, permeation transients were much faster in HT-9 than in other materials tested. Sputtering of the steel surface resulted in enhanced reemission, whereas in the vanadium tests, recombination and diffusivity both appeared to diminish as the deuterium concentration rose. We conclude that for conditions comparable to those of these experiments, tritium retention and permeation loss in first wall structures made of steels will be less than in structures made of V-15Cr-5Ti.

This paper presents a comparison of the hydrogen permeation properties of the austenitic primary candidate alloy, PCA, and of the advanced ferritic alloy, HT-9. The comparison is based on experimental measurements of the permeation and reemission of deuterium from specimens undergoing implantation with 3-keV, D/sub 3//sup +/ ions produced by an accelerator. Characterization of the specimen surface facing the ion beam is provided by secondary ion mass spectrometer (SIMS) analysis of the species sputtered from the surface during the implantation. Recombination and diffusivity data for PCA and HT-9 were derived from an analysis in which model calculations were applied to the reemission and permeation measurements.