A Japanese peace research institute discovered in March that an additional subcritical nuclear test was added to a U.S. tally due to a change in its criteria, with a series of plutonium experiments from 2007 now being grouped together to represent a single test. Peace Depot Inc., based in Yokohama near Tokyo, filed a request last September with the U.S. Department of Energy’s National Nuclear Security Administration under the Freedom of Information Act to disclose the details after it was revealed last year that the number of U.S. subcritical nuclear tests had risen from a total of 32 to 33. J…