In preparation for and in support of a detailed R and D Plan for the Accelerator-Based Conversion (ABC) of weapons plutonium, an ABC Plant Layout Study was conducted at the level of a pre-conceptual engineering design. The plant layout is based on an adaptation of the Molten-Salt Breeder Reactor (MSBR) detailed conceptual design that was completed in the early 1070s. Although the ABC Plant Layout Study included the Accelerator Equipment as an essential element, the engineering assessment focused primarily on the Target; Primary System (blanket and all systems containing plutonium-bearing fuel salt); the Heat-Removal System (secondary-coolant-salt and supercritical-steam systems); Chemical Processing; Operation and Maintenance; Containment and Safety; and Instrumentation and Control systems. Although constrained primarily to a reflection of an accelerator-driven (subcritical) variant of MSBR system, unique features and added flexibilities of the ABC suggest improved or alternative approaches to each of the above-listed subsystems; these, along with the key technical issues in need of resolution through a detailed R&D plan for ABC are described on the bases of the ``strawman`` or ``point-of-departure`` plant layout that resulted from this study.

The free energy, enthalpy and entropy of formation of the compounds Cs3PuCl6 and CsPu2Cl7 have been determined by measuring the sublimation pressures for the reactions CsCl(s) /aiCsCl(g), 25Cs3PuCl6(s) /ai 15CsPu2Cl7(s) + CsCl(g), and CsPu2Cl7(s) /ai 2PuCl3(s) + CsCl(g). The pressures are measured using Knudsen effusion mass spectrometry over the temperature range 600 to 850 K. For the formation of Cs3PuCl6 from CsCl and PuCl3, ΔG0298 = −77.3 ± 8.5 kJ/mol, ΔH0298 = −82.1 ± 7.8 kJ/mol, and ΔS0298 = −16.2 ± 10.9 J/Kmol. For CsPu2Cl7, ΔG0298 = −39.4 ± 3.5 kJ/mol, ΔH0298 = −40.8 ± 3.2 kJ/mol, and ΔS0298 = −4.6 ± 4.2 J/Kmol.