Granulation of Dried Borate Concentrates from Nuclear Power Plants

Borate concentrated wastes generated from liquid waste evaporator of 12 pressurized water reactors (PWRs) have been processed to be dry using concentrated waste drying system (CWDS) in Korea. Borate wastes had been stabilized or solidified using paraffin as a binder since 1995, but the solidification process is stopped and concentrated wastes are just stored in drums and on standby at present because paraffin waste forms have some sorts of problems such as heterogeneous forming (stratification), low compressive strength, and high leaching rate [1]. According to No. 2005-18 of Notices of the Ministry of Science and Technology (MOST), all of lowand intermediate level waste (LILW) forms must satisfy the requirement of solidification before they are delivered to the final repository in Kyeongju [2]. In this study, polymer solidification technology is proposed to treat borate concentrated wastes. Originally, this technology has been developed and used to solidify the spent ion exchange resin in many countries. Most commercial polymer binders include epoxy, polyester and vinylester styrene, etc. Recently in May 2003, Idaho National Engineering and Environmental Laboratory (INEEL) issued a report confirming that APSTM (Diversified Technologies Services), a kind of polymer waste form, met the NRC’s Waste Form requirements for Class B and C wastes. The Conference of Radiation Control Program Directors (CRCPD) reviewed the INEEL report, and the E-5 Committee issued a letter of waste form approval for the APSTM process. This serves as a national approval in the US, replacing the nowdefunct NRC Topical Report Program. Granulation of dried powder waste is prerequisite for the successful operation of polymer solidification process. Granular wastes permit the maximum waste loading, in situ process without in-line mixing or indrum mixing, easy workability without dispersion of contaminants, and possible connections with CWDS. A feasibility study on the granulation of dried borate wastes using liquid sodium silicate as a granulating agent was performed.