A man holds his mask while he is tested for possible nuclear radiation at an evacuation centre in Fukushima, northern Japan, April 4, 2011. Japan's government on Monday told the operator of the crippled Fukushima nuclear plant to move quickly to stop radiation seeping into the ocean as desperate engineers resorted to bath salts to help trace a leak from one reactor. REUTERS/Kim Kyung-Hoon (JAPAN - Tags: DISASTER POLITICS HEALTH)