Sentence:  recommend to the Congress from time to time authorization for construction and operation , or for participation in the construction and operation , of a demonstration plant for any process which he determines , on the basis of subsections ( a ) and ( b ) above , has great promise of accomplishing the purposes of this Act , such recommendation to be accompanied by a report on the <WSD>size</WSD> , location , and cost of the proposed plant and the engineering and economic details with respect thereto ; 
Meaning of the word marked with <WSD> tags:  the physical magnitude of something (how big it is)