Martin Liezers

Rhenium Solubility in Borosilicate Nuclear Waste Glass: Implications for the Processing and Immobilization of Technetium-99

The immobilization of technetium-99 ((99)Tc) in a suitable host matrix has proven to be a challenging task for researchers in the nuclear waste community around the world. In this context, the present work reports on the solubility and retention of rhenium, a nonradioactive surrogate for (99)Tc, in a sodium borosilicate glass. Glasses containing target Re concentrations from 0 to 10,000 ppm [by mass, added as KReO(4) (Re(7+))] were synthesized in vacuum-sealed quartz ampules to minimize the loss of Re from volatilization during melting at 1000 °C. The rhenium was found as Re(7+) in all of the glasses as observed by X-ray absorption near-edge structure. The solubility of Re in borosilicate glasses was determined to be ~3000 ppm (by mass) using inductively coupled plasma optical emission spectroscopy. At higher rhenium concentrations, additional rhenium was retained in the glasses as crystalline inclusions of alkali perrhenates detected with X-ray diffraction. Since (99)Tc concentrations in a glass waste form are predicted to be <10 ppm (by mass), these Re results implied that the solubility should not be a limiting factor in processing radioactive wastes, assuming Tc as Tc(7+) and similarities between Re(7+) and Tc(7+) behavior in this glass system.

RadICalc: a program for estimating radiation intensity of radionuclide mixtures

RadICalc was developed to address the need for a computer program that could calculate the composition, activity, and measurable radiation of arbitrary radionuclide mixtures over time without significant effort from end-users. It provides an interface to perform decay calculations and can search and display the resulting data in graphical or tabular form. RadICalc can also determine radiation expected at specific masses with user-defined molecules in addition to atomic species for use in mass-based isotope separations for radiometric counting applications, a novel method under development at Pacific Northwest National Laboratory.

The preparation of non-radioactive glassy surrogate nuclear explosion debris (SNED) loaded with isotopically altered Xe

The measurement of Kr and Xe isotope ratios in nuclear explosion debris can be performed requiring little sample preparation. Fragments of debris are simply crushed or heated to release trapped gases Kr and Xe arising from fission product decay. As a suitable test material for this measurement, we have been investigating a method to incorporate isotopically enriched 129Xe in glassy materials that mimic nuclear explosion debris. The approach used to prepare these materials will be described along with some of the example results obtained.

LA-ICP-MS analysis of plastics as a method to support polymer assay in the assessment of materials for low-background detectors

Ultra low-background radiation measurements are essential to several large-scale physics investigations. Assay of solid polymer materials for extremely low levels of radioactive elements, such as uranium, presents challenges. This paper describes an initial investigation into the use of laser ablation with inductively coupled plasma mass spectrometry for screening a solid plastic, polyethylene, for gross uranium levels.

Alpha spectrometry applications with mass separated samples.

(241)Am has been deposited using a novel technique that employs a commercial inductively coupled plasma mass spectrometer. This work presents results of high-resolution alpha spectrometry on the (241)Am samples using a small area passivated implanted planar silicon detector. We have also investigated the mass-based separation capability by developing a (238)Pu sample, present as a minor constituent in a (244)Pu standard, and performed subsequent radiometric counting. With this new sample development method, the (241)Am samples achieved the intrinsic energy resolution of the detector used for these measurements. There was no detectable trace of any other isotopes contained in the (238)Pu implant demonstrating the mass-based separation (or enhancement) attainable with this technique.

FY 2009 Progress: Process Monitoring Technology Demonstration at PNNL

Pacific Northwest National Laboratory (PNNL) is developing and demonstrating three technologies designed to assist in the monitoring of reprocessing facilities in near-real time. These technologies include 1) a multi-isotope process monitor (MIP), 2) a spectroscopy-based monitor that uses UV-Vis-NIR (ultraviolet-visible-near infrared) and Raman spectrometers, and 3) an electrochemically modulated separations approach (EMS). The MIP monitor uses gamma spectroscopy and pattern recognition software to identify off-normal conditions in process streams. The UV-Vis-NIR and Raman spectroscopic monitoring continuously measures chemical compositions of the process streams including actinide metal ions (uranium, plutonium, neptunium), selected fission products, and major cold flow sheet chemicals. The EMS approach provides an on-line means for separating and concentrating elements of interest out of complex matrices prior to detection via nondestructive assay by gamma spectroscopy or destructive analysis with mass spectrometry. A general overview of the technologies and ongoing demonstration results are described in this report.

Simulating the effects of underground nuclear explosions with an exploding wire

Exploding wires can deposit significant amounts of energy on nS–µS timescales into a confined space. Most exploding wire studies have been performed in air but we have started to investigate enclosing the wire element in solid matrices like concrete to mimic the effects of an underground nuclear explosion. Temperatures and pressures achieved are quite sufficient to induce structural cracking and localized flash melting. As a result exploding wires would appear to form the perfect trigger for releasing chemical species in geological media to study migration behavior. Details of the apparatus and some illustrations of its potential will be given.