TOKYO (AP) -- The crippled reactors at Japan's tsunami-hit nuclear power plant have reached stability more than four months since the disaster and the plant is on track for a cold shutdown within six months, the government and plant operator said.
Workers have toiled in hot and harsh conditions to stabilize the Fukushima Dai-ichi plant since the March 11 earthquake and tsunami destroyed reactor cooling systems, triggering partial meltdowns of the reactors and making the disaster the world's worst nuclear crisis since Chernobyl.
The assessment of reactor stability was based on several milestones: temperatures at the bottom of reactor pressure vessels are no longer climbing, a makeshift system to process contaminated water works properly after initial problems and nitrogen injections are helping prevent more explosions.
Radiation around the plant has shown a "sufficient decrease" from peak levels measured soon after the disaster, according to the report released Tuesday by the government and TEPCO, the plant's operator.
The progress achieves TEPCO's initial goals of its road map to bring the plant under control, the report said.
"The accident has not been resolved, but we have been making progress steadily," trade and industry minister Banri Kaieda said. "We will continue our utmost effort so that we can bring this to an end as soon as possible."
The work now shifts into a second stage, when workers will aim to further cut radiation released into the air, soil and water. They expect a cold shutdown sometime in January.
A reactor reaches cold shutdown when the temperature at the bottom of the reactor pressure vessel drops below 100 degrees Celsius, and when the release of radioactive materials is "under control."
TEPCO also said it would continue to improve conditions for workers by expanding temporary dormitories and onsite rest stations, as well as stronger controls over their radiation exposure.
Still, growing worries about radiation in Japan's beef supply underscore the widespread impact of the nuclearaccident.
The central government instructed Fukushima to suspend shipment of all beef cows raised in the prefecture.
The move comes amid a growing tally of cows -- now about 650 -- that were fed radiation-tainted rice straw and then shipped nationwide. Some of the meat has already reached consumers.
Major supermarket chain Aeon acknowledged over the weekend that 14 of its outlets in Tokyo and nearby prefectures sold meat from the exposed cows between April and June.
Chief Cabinet Secretary Yukio Edano said the contamination stems from rice straw that had been sitting outside since the March 11 disaster, then fed to the cattle.
Fukushima officials have said they did not properly inform farmers to avoid using feed stored outdoors.
Cesium levels exceeding the legal limit has been detected in beef samples in three cities.
"We are doing utmost to track down beef that might have been fed rice straw," Edano said. "If we find any samples we will suspend it from distribution and inspect."