the first experiments with the use of ultracentrifuges for enriching uranium were executed by the dutch physicist dr. jacob kistemaker in the basements of werkspoor in amsterdam. this finally led to founding the uranium enrichment plant urenco in almelo in 1969. in the 1970s werkspoor built the reactor pressure vessel for the kema suspensie test reactor (kstr), an experimental nuclear reactor used by kema in arnhem from 1974-1979 for studies.