Determination of Transmutation Effects in Crystalline Waste Forms

Technical Report · Fri Dec 31 00:00:00 EST 1999

DOI:https://doi.org/10.2172/828342· OSTI ID:828342

Fortner, Jeffrey A

The overall goal of this Environmental Management Science Program project was to develop research tools to investigate the effect of transmutation, that is, the radioactive decay of a radioisotope to an isotope of another element, on the stability of a crystalline matrix. This process is an important issue in the assessment of the long-term stability, and hence performance, of a waste form. Most work on radiation effects in waste forms has focused on alpha radiation, which produces more displacements than beta radiation. However, beta radiation results in transmutation, which changes both the valence and the ionic radius of the element undergoing decay. These changes in coordination chemistry may destabilize the waste form and hence permit higher releases of the radionuclide contaminants to the accessible environment. Little is known about the mobility of Cs in pollucite. Only a few studies [1-3] have examined leaching following transmutation or irradiation of pollucite or closely related aluminosilicates. These studies seem to have contradictory results. The results may indicate that prior to radiation-induced amorphization, the accumulated defects may lead to higher leachability of Cs [3], whereas once amorphization occurs, the Cs becomes trapped in the collapsed structure [2]. A more thorough analysis of the effect of accumulated defects from both transmutation and ionization processes on the pollucite structure is needed to assess to the impact on Cs mobility. In this three- year research program, we used cutting-edge experimental approaches to investigate this little-understood issue. The work was a collaboration between Argonne National Laboratory (ANL) and Pacific Northwest National Laboratory (PNNL). We focused on the effects of transmutation on pollucite (CsAlSi2O6), a cesium aluminosilicate that has been proposed for the long-term immobilization of radioactive cesium. In this ceramic waste form, the 137Cs decays to 137Ba, causing barium to build up in the pollucite samples over time. We selected pollucite for this study for the following reasons: We had access to several well-characterized samples of 137Cs containing pollucite that had been stored under ambient conditions for up to 20 years. Cesium has a high activity (t1/2 = 30.13 years), leading to the buildup of significant levels of Ba in these samples. Cesium continues to be an important constituent of the waste management effort within the DOE complex.

• Research Organization: Argonne National Lab., Argonne, IL (US)
• Sponsoring Organization: USDOE Office of Environmental Management (EM) (US)
• OSTI ID: 828342
• Report Number(s): EMSP-55382; R&D Project: EMSP 55382; TRN: US0403934
• Resource Relation: Other Information: PBD: 31 Dec 1999
• Country of Publication: United States
• Language: English

Related Subjects

12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
54 ENVIRONMENTAL SCIENCES
BARIUM
CERAMICS
CESIUM
DECAY
IONIZATION
IRRADIATION
LEACHING
POLLUCITE
RADIATION EFFECTS
RADIATIONS
RADIOISOTOPES
RESEARCH PROGRAMS
STABILITY
TRANSMUTATION
VALENCE
WASTE FORMS
WASTE MANAGEMENT