40 Years of Doubts About Mark I Containment

March 15, 2011
David Wright
Former contributor

The New York Times ran a story today citing memos from September 1972 by officials in the Atomic Energy Commission, the forerunner of the Nuclear Regulatory Commission (NRC), showing longstanding concerns about the ability of reactors like those at Fukushima Dai-Ichi to contain a nuclear accident.

These documents and others that raise questions about the Mark I and similar pressure-suppression containment systems for reactors are likely to spur a discussion of its safety in the U.S. and elsewhere.

In the U.S., there are currently 35 operating boiling-water reactors, all of which use pressure-suppression containment. Of these, 23 reactors use the Mark I. In addition, there are 9 pressurized-water reactors operating in the U.S. that use ice-condenser containment, which has the same shortcomings.

The 1972 documents linked to by the NYT story were originally obtained by UCS through a FOIA request. UCS released them publicly with a press release in October 1972 – the month following the exchange of memos.