Enriched uranium technology at the Sillamäe oil shale processing plant

The shale oil factory at Sillamäe, Estonia was founded in 1928 by the “Estonian Oil Consortium”, belonging to Swedish capital. It is the only factory that has processed both the brown (kukersite) oil shale and the black (dictyonema) shale that are both abundant in Estonia. The much older black shale contains, besides the oil-bearing organic material, significant amounts of various heavy metals, including uranium, and is therefore radioactive. Uranium-based nuclear technology has dominated the second half of the last century, but now faces potential competition from the emerging hydrogenbased energy technologies. It is little known that the Sillamäe Oil Shale Plant has played a significant role in the development of the gas cooled very high temperature pebble bed reactor for direct production of either hydrogen or electricity. We analyze here the timeline of this development effort.