Global Security Newswire

Japan on Friday announced discoveries of plutonium as far as 28 miles from the crippled Fukushima Daiichi atomic facility, an initial verification that the toxic element had escaped the crippled site, Kyodo News reported (see GSN, Sept. 30).

The power plant was damaged by the March 11 earthquake and tsunami that left roughly 20,000 people missing or dead in Japan. Radiation releases on a level not seen since the 1986 Chernobyl disaster forced the evacuation of about 80,000 residents from a 12-mile ring exclusion zone surrounding the site.

The plutonium turned up in soil at Iitate village, located 28 miles northwest of the plant, and at five other points in Japan's Fukushima prefecture. The element is considered a significant cancer threat to humans as an internal contaminant, but Japanese Science Ministry officials said measured quantities of the material were inconsequential from a wellness standpoint (Kyodo News I/Japan Times, Oct. 1).

Some plutonium isotopes decay at a rate of 50 percent every 24,000 years, while other variants break down in equal quantity in as few as 88 years, the Wall Street Journal reported on Sunday (Toko Sekiguchi, Wall Street Journal, Oct. 2). Plutonium 239 and plutonium 240 -- isotopes with respective half-lives of 24,000 and 6,600 years -- were found in combined quantities as high as 15 becquerels per square meter in Minamisoma city, Kyodo reported (Kyodo News II/Mainichi Daily News, Oct. 2).

"Because the fuels (in the reactors) melted down, plutonium may have been emitted with steam or other small particles and sent airborne," said a source with Tokyo Electric Power, the Fukushima plant's operator. "(Judging by the amount of plutonium) it is believed to be from the accident" (Kyodo News I).

In addition, authorities in one case found radioactive strontium 50 miles from the facility, the Science Ministry said in a report.

Cesium and iodine comprise the bulk of contaminants found so far outside the plant, the Journal reported. Plutonium and strontium released "extremely low" radiation relative to the higher quantity of cesium, says the ministry's assessment, which recommends that Tokyo continue emphasizing the detection of cesium and its removal from the environment (Sekiguchi, Wall Street Journal, Oct. 2).

Cesium 137 concentrations ranged from 30,000 to 60,000 becquerels per square meter in areas of Chiba and Saitama prefectures, territories roughly 125 miles from the plant, the Asahi Shimbun reported. The cesium isotope breaks down at a rate of 50 percent over three decades (Hisae Sato, Asahi Shimbun I, Oct. 1).

Atomic fuel at the Fukushima plant could begin breaking down and releasing radioactive contaminants 38 hours after a potential halt to coolant insertion, Tokyo Electric Power said in a projection reported by Kyodo on Sunday.

Still, the company said it would require no longer than three hours to restart cooling operations at the plant's No. 1, No. 2 and No. 3 reactors if events equivalent to those of March 11 impacted the site (Kyodo News III/Mainichi Daily News, Oct. 2).

"We have little choice but to keep reactors under the cold shutdown without much change (in the reactor control systems)," Nuclear and Industrial Safety Agency Director General Hiroyuki Fukano told the Asahi Shimbun on Friday. In "cold shutdown," the plant's reactors would retain heat levels below 100 degrees Celsius, and radioactive contaminant emissions would be drastically curtailed.

"The plant is using some makeshift equipment now," Fukano said. "That raises fears that those units could be easily destroyed by another earthquake. We need to assess our backup systems for the equipment should the units be knocked out by an earthquake" (Tatsuyuki Kobori, Asahi Shimbun II, Oct. 1).

An internal assessment indicates the company's crisis management guidelines were of no utility in responding to the disaster, Kyodo reported on Sunday (Kyodo News IV/Mainichi Daily News, Oct. 2).