The methods for the separation of the elements from thorium to americium having wide use are those employing solvent extraction techniques (1) (2). During recent years the behavior of these elements on anion exchangers has been studied, resulting in the wide application of these resins to the separation of the actinides (3) (4) (5) (6) (7).

The instability of the steel tank bottom of 113SX waste storage tank was postulated to have been caused by a pressure underneath the steel liner which was in excess of the hydrostatic liquid load of the waste resting on the steel bottom.

In HW-56161(1), the preliminary background, bases, and advantages which could be visualized in the study and establishment of reactor concepts utilizing boiling mercury- 204 were presented. The attractive chemical and metallurgical properties of mercury which make it particularly suitable for use in special non-rigid fuel systems as well as its potential for heat transfer applications were considered to be of significant interest to the Plutonium Recycle Program also, since the issuance of the original document, continued study of the potentials for an economical isotope separations process for mercury has shown attractive possibilities for a method based on photochemical activation (HW-59329). (2) The prospectas(3) for this process appear so favorable that earlier opinions and expectations seem to have been conservative. Although the desired level of initial effort in related studies has not yet been realized, particularly in the area of chemical engineering, reactor engineering, and economics, it appears advisable to revise the earlier document to recognize the impact of the favorable outlook for economical mercury isotope production, to present other related information which has been developed, and to recommend the beginning of a research and development program.

Over the past ten years, there has been considerable interest and expenditure on the recovery of ionium (thorium-230) from certain residues accumulated from the World War II uranium process at St. Louis, Missouri. Most of these efforts were reported in the classified literature. However, an unclassified report was issued recently by the Mallinckrodt Chemical Works on the plant design for ionium recovery. A review of the earlier efforts shows that consideration of ionium recovery was limited to the St. Louis residues. At that time the development of a substantial U. S. uranium ore milling industry had not yet been achieved.