Extraction of gadolinium from high flux isotope reactor control plates

Author

Mark W. Kohring

Date of Award

3-1987

Degree Type

Thesis

Degree Name

Master of Science

Major

Nuclear Engineering

Major Professor

Hall C. Roland

Abstract

Gadolinium-153 is an important radioisotope used in the diagnosis of various bone disorders. Recent medical and technological developments in the detection and cure of osteoporosis, a bone disease affecting an estimated 50 million people, have greatly increased the demand for this isotope.

The Oak Ridge National Laboratory (ORNL) has produced ¹⁵³Gd since 1980 primarily through the irradiation of a natural europium-oxide powder followed by the chemical separation of the gadolinium fraction from the europium material. Due to the higher demand for ¹⁵³Gd, an alternative production method to supplement this process has been investigated. This process involves the extraction of gadolinium from the europium-bearing region of highly radioactive, spent control plates used at the High Flux Isotope Reactor (HFIR) with a subsequent re-irradiation of the extracted material for the production of the ¹⁵³Gd.

The ORIGEN2 computer code was used to predict the gadolinium and europium isotopic concentrations and compositions at various axial positions along one spent HFIR control plate. The calculational results, although based on rough estimates of the perturbed neutron flux intensities present at each local site, supported the decision to proceed with the experimental determination of the viability of the proposed supplemental ¹⁵³Gd production scheme.

To initiate the research, one spent control plate was assayed at several axial positions. At each location, a gamma scan was conducted to determine the relative intensity of the radioactive europium and gadolinium isotopes. From this information, the region of peak ¹⁵²Gd concentration could be inferred from the maximum activity levels of its parent isotope, ¹⁵²Eu, and its activation product, ¹⁵³Gd. The control plate was cut into thin strips for further evaluation. Following separation of the gadolinium and europium elements from each strip, a mass spectrographic analysis was made on each sample to obtain the isotopic composition. Based on these analyses, the "lower bound" to the usable portion of the control plate for ¹⁵²Gd extraction could be established. A "best fit" correlation between axial control plate location and an "effective" total neutron exposure over the plate lifetime was obtained and judged as sufficient for obtaining estimates of the gadolinium concentrations of other control plates.

Based on the results of the experimental and calculational analyses, up to 25 grams of valuable gadolinium (≥ 60 percent enriched in ¹⁵²Gd) resides in the europium-bearing region of the HFIR control components of which 70 percent is recoverable. At a specific activity yield of 40 curies of ¹⁵³Gd for each gram of gadolinium re-irradiated, 700 one-curie sources can be produced from each control plate assayed.

Recommended Citation

Kohring, Mark W., "Extraction of gadolinium from high flux isotope reactor control plates. " Master's Thesis, University of Tennessee, 1987.
https://trace.tennessee.edu/utk_gradthes/13506