The presence of significant amounts of molybdenum in high level waste (HLW) streams can lead to the formation of a molybdate salt phase ("yellow phase") during vitrification. These salts are undesirable from both melter operations and product quality perspectives, such that yellow phase formation can become the primary factor that limits waste loading in the HLW glass product. The Rokkasho Reprocessing Plant, located in northern Japan, includes facilities for reprocessing commercial spent nuclear fuel and conversion of the HLW into a stable glass waste form by vitrification. The primary objectives of the present study were to characterize yellow phase formation with projected Japanese HLW streams and to develop suppression strategies that could permit both more robust operations and the potential for increased waste loadings. The testing was divided between approaches that would not change the present baseline product glass composition and those that involve the modification of that composition. The former approach involves the least change and therefore could be implemented more quickly. Testing was performed using a combination of crucible scale glass melts, vertical gradient furnace tests, and scaled joule heated ceramic melter tests to develop viable strategies for yellow phase control that are being subjected to full-scale testing prior to deployment in the Rokkasho facility.

Hao Gan

Keith S. Matlack

Ian L. Pegg

Innocent Joseph

Bradley W. Bowan

Yoshiyuki Miura

Norio Kanehira

Eiji Ochi

Toshiro Oniki

Yoshihiro Endo

Ceramic Transactions Series

Ceramic Transactions

Suppression of Yellow Phase Formation During Japanese HLW Vitrification

日本高放废液玻璃固化过程中黄相形成的抑制

Suppression of Yellow Phase Formation During Japanese HLW Vitrification

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