An agreement permitting Japan to fly plutonium from Europe to Japan without U.S. approval of each shipment goes into effect Sunday.

The plutonium is derived from U.S.-supplied nuclear reactor fuel. Critics have said the shipments, not expected to begin until the 1990s, increase the chance that terrorists someday could get their hands on enough plutonium to build a nuclear weapon.No shipping container to hold the radioactive plutonium has been designed yet.

Japan plans to use the plutonium, which is produced during the fission of uranium fuel supplied by the United States, to supplement uranium fuel and later for "breeder" reactors which produce more plutonium from normally unusable uranium.

The spent uranium fuel has been shipped to French and British companies for several years for removal of the plutonium, which has been slowly accumulating there. Japan plans its own reprocessing plant to take over the plutonium removal.

Some forms of plutonium, which does not occur in nature, are produced in the fission of uranium. If breathed, plutonium and its compounds can cause lung cancer.

The Nuclear Regulatory Commission, the Defense Department, the Senate Foreign Relations Committee and the General Accounting Office all opposed the new agreement.