PRTR accident: a preliminary report on the investigation of fission product chemical forms. [Fuel Element Rupture Test Facility]

The central process tube of PRTR was independently cooled by light water and functioned as a Fuel Element Rupture Test Facility (FERTF). On September 29, 1965, the FERTF was experimenting with a mixed uranium-plutonium oxide fuel element in which one rod had been purposely defected by drilling a 1/16 inch hole through the Zircaloy cladding to the fuel surface. The combined failure of the partially molten fuel rod and rupture of the surrounding process tube allowed superheated cooling water to flash into the low pressure helium region of the reactor core and subsequently leak into the containment vessel. At the request of the US NRC, PNL is reviewing the PRTR incident to assemble and update all the information available regarding the volatile and semi-volatile fission products released to discover and investigate any clues that remain which may indicate the most probable chemical and physical forms of these released fission products. This review is now half completed and has involved both an experimental study, which is complete, and a literature analysis, still in progress.