[en] In September of 1965, an intentionally defective fuel rod failed in the Plutonium Recycle Test Reactor (PRTR), causing the rupture of the surrounding pressure tube and the release of superheated cooling water into a region of the reactor core. The Pacific Northwest Laboratory (PNL) has reviewed the PRTR incident to assemble and update all the available information regarding the incident. A principal goal of the review was to analyze any remaining clues that may indicate the stoichiometry or most probable chemical and physical forms of the released fission products. The review confirmed the role of water in limiting iodine release. About 97% of the iodine released during the accident was subsequently found in tanks containing the reactor/rupture-loop coolant. Although the chemical form of the released radioiodine cannot be stated unambiguously, the available evidence suggests that it was released in the form of cesium iodide. Most of the remaining 3% was found in the condensate collected from air cooling systems. The chemical form of this scrubbed iodine remains undefined