TOKYO, June 15 (Reuters) - Japanese nuclear operators want to curb stockpiles of plutonium extracted from spent nuclear fuel by using them as feedstock for reactors, the industry's top official said on Friday.
He was responding to a media report that the United States has called on Tokyo to reduce its mounting stockpiles.
The Nikkei business daily, citing unidentified sources familiar with the matter, reported on Sunday that the U.S. Department of State and the National Security Council had requested that Japan trim its stockpiles ahead of an extension next month of a bilateral nuclear cooperation agreement.
Japan is also the only nation without atomic weapons to have significant amounts of plutonium, which has led to constant criticism from neighbouring countries, scientists and others.
The chairman of the Japanese power utilities' federation, Satoru Katsuno, who is also president of Chubu Electric Power , said he was not aware of such diplomatic discussions and added that Japanese utilities had not received any request from the Japanese government to set an upper limit on plutonium stockpiles.
"Under the principle of not having plutonium with no purpose for usage, we are trying to carry out MOX (mixed oxide) fuel usage at reactors promptly. We will continue to try to curb plutonium stockpiles," he said during his monthly news conference in Tokyo.
Chubu Electric wants to use its plutonium stockpiles as fuel for its Hamaoka No.4 reactor, which has been shut pending rigorous safety checks imposed after the Fukushima disaster in 2011, he said.
With most of Japan's commercial reactors still shut down in the wake of the Fukushima nuclear disaster, the stockpiles have been gradually building up.
At the end of 2016, Japan had 46.9 tonnes of plutonium, including 9.8 tonnes domestically and the rest held in reprocessing facilities in Britain and France under contracts with Japanese nuclear operators, according to the latest available data from the Cabinet Office.
Japan says it has firmly maintained the principle of not owning plutonium whose use is unspecified and of putting all nuclear materials under the International Atomic Energy Agency's safeguards, in accordance with the Nuclear Non-Proliferation Treaty.
Only a limited number of reactors in Japan can use MOX in reactors, but the use of MOX - a blend of uranium and plutonium recycled from spent nuclear fuel - in conventional commercial reactors is a pillar of resource-poor Japan's energy policy. (Reporting by Osamu Tsukimori; Editing by Susan Fenton)