[en] The primary objective of the balance-of-plant technical effort during Phase A Extension was to perform design work for a 1000 MWe (gross) pool type LMFBR to obtain an integrated plant design with emphasis of pool related structures and systems that differ from a loop type LMFBR or are of special concern. This report describes the general arrangement of major structures and equipment that are supported on a common foundation mat and the containment auxiliary systems that are unique or essential for the pool concept. Installation of major pool components during construction and containment design features that permit removal of major pool-related equipment are also described