Japan neglected carrying out safety checks on at least 40 percent of nuclear reactor parts exported over a decade, a report said Monday, in the latest controversy to strike its troubled nuclear industry.

Nuclear reactor parts -- including pressure vessels which contain the fuel in power plants -- worth about 51.1 billion yen ($520 million) were shipped to 17 countries, as well as Taiwan, without undergoing safety checks, the Mainichi Shimbun newspaper reported.

Britain, Germany, Australia, Russia and Italy were among the countries that took delivery of the potentially unsafe equipment, the daily said, citing manufacturers and an industrial body among its sources.

Japan exported nuclear reactor parts worth 124.8 billion yen to more than 20 countries from 2003-2012, the Mainichi Shimbun said, citing official trade figures.

But safety checks, entailing simple examinations of documents, were only required for exports tied to loans from the state-run Japan Bank for International Cooperation or guarantees by the public agency Nippon Export and Investment Insurance, the daily said.

The unchecked parts included reactor pressure vessels shipped to Taiwan in 2004 and control rod drives, which regulate the rate of nuclear fission, supplied to Sweden and Brazil, Mainichi said.

The rest of the exports are thought to have undergone government safety checks before being shipped to China, the United States, France, Belgium and Finland, the daily said, citing the country's Agency for Natural Resources and Energy.

But much of the data disclosed by the agency was blacked out, raising the possibility that those exports may too have been shipped without being checked, Mainichi said.

Safety has been a huge concern for Japan's nuclear industry since a massive earthquake and tsunami ravaged the country's northeast coast and triggered a meltdown at the Fukushima nuclear power plant in March 2011.

But the country has continued overseas sales of nuclear reactor technology, with Prime Minister Shinzo Abe assuring buyers the industry is among the world's safest.