TMI-2 Core materials and fission product inventory

Investigations of the melting behaviour of the U–Zr–Fe–O system

“…In the Three Mile Island unit 2 (TMI-2) reactor it was estimated that the inventory of UO 2 fuel was 94,000 Kg and that of Zircaloy-4 cladding was 24,000 Kg, this corresponds approximately to the molar ratio UO 2 /Zr of 0.67 [21]. Simple calculations of a cladded un-irradiated pressurised water reactor (PWR) fuel cross-section give a similar ratio of 0.66.…”

A Brief Review of Past INL Work Assessing Radionuclide Content in TMI-2 Melted Fuel Debris: The Use of 144Ce as a Surrogate for Pu Accountancy

“…Principal subjects included the relocation of core materials out of the reactor vessel, the formation of complex core material interaction products, cesium retention in prior molten material, and the retention of tellurium, antimony, and ruthenium in association with core materials. [5] The key findings of this report are the following.…”

“…[5] The composition data indicate that during the accident much of the core structural materials relocated within the core volume. o Zirconium and structural materials relocated to form the crusts and metallic inclusions present in the lower part of the reactor core.…”

“…Table 2 Low-volatility fission product distribution in the TMI-2 reactor system. [5] a) Percentage of the total amount of the fission product inventory calculated from comparisons with ORIGEN2. b) Insignificant amount (< 0.1 wt%) based on the measurement data.…”

Pyrochemical fuel cycle technologies for processing of spent nuclear fuels

“…According to "the Mid-and-Long-Term Roadmap towards the Decommissioning of TEPCO's Fukushima Daiichi Nuclear Power Station Units 1-4" issued by the Japanese government, processing and/or disposal methods for fuel debris are planned to be determined in parallel to removal of it from reactor cores. According to the evaluation of core materials and FP inventory after the TMI-2 accident (Akers et al, 1990), heat-generating FPs such as cesium and strontium, which tend to accumulate in molten salt solvents used in pyrochemical processes, are expected to have been remarkably decreased from the corium due to the core melting at high temperature and long-term leaching into injected and circulated cooling water. The chemical analyses of the corium samples obtained from the TMI-2 damaged core, which mainly consist of (U,Zr)O 2 , have shown that it is hard to dissolve them into nitric acid (Akers et al, 1986).…”