Japan: Second Nuclear Reactor At Risk Of Exploding

Written by: Eurasia Review

Government officials say as many as 160 people may have been exposed to radiation in Fukushima Prefecture

Japan is struggling to keep nuclear power reactors under control. This comes as massive search and rescue efforts are underway in the northeastern part of the country following Japan’s worst ever natural disaster.

The official death toll is now over 1,000 with thousands more people unaccounted for and 300,000 Japanese evacuated from severely damaged communities following Friday earthquake and large tsunami.

Government officials early Sunday said as many as 160 people may have been exposed to radiation here in Fukushima Prefecture. That occurred following an explosion at the crippled number one plant of the Fukusihma nuclear power complex.

It apparently happened as the result of steps taken to try to prevent the reactor melting after the facility lost power as a result of the quake and tsunami. Plant operators initiated a desperate measure to cool the number one reactor using seawater and boric acid. Government officials say the containment vessel around the reactor’s core is intact.

On Sunday, Japan’s nuclear safety agency reported an emergency at a second reactor here. And there are domestic media reports that up to six reactors in all here in Fukushima Prefecture have lost their cooling function. Worries of meltdowns of reactors is now overshadowing the search and rescue efforts following the mega-quake and resulting tsunami that has devestated hundreds of kilometers of Japan’s pacific northeastern coast.

Prime Minister Naoto Kan Saturday evening addressed Japan expressing hope that as he put it this disaster can somehow be survived. Besides helping the thousands of people injured and made homeless by the quake and tsunami, he said his top priority is the emergency with the damaged nuclear power plants here in Fukushima Pretecture.

But the government is facing mounting criticism for delayed and partial information, generating skepticism about whether they are being totally forthcoming about the total extent of the crisis. A 20-kilometer evacuation zone has been established at the number one reactor and a 10 kilometer zone around a second one.

About 170,000 people have been moved out of the danger area. For most survivors however the immediate concern is not about potential radiation exposure. They are just trying to get by with life. More than one million households are expected to have been without water since the quake hit. Food supplies are dwindling, with many countryside communities cut off. They are surrounded by water or roads have been damaged.

The death toll remains unclear. Troops are finding hundreds of bodies along the beaches where tsunamis swept out to sea entire communities in neighboring Iwate and Miyagi prefectures. Other rescuers in helicopters are lifting people one by one who were stranded atop damaged buildings.

About 50,000 Japanese troops are to get assistance from foreign teams which are converging on northeastern Japan. More than 50 countries have offered help.

The nuclear plants in Japan

Nuclear Emergency in Japan

Posted: March 12, 2011

The recent earthquake in Japan has triggered an actual nuclear emergency at the Fukushima Daini nuclear power plant. According to IAEA, the explosion earlier today originated in the Unit 1 reactor building and was not the result of explosive breach of the primary containment. One character interviewed on CNN called it a six sigma event.

If memory serves, water dissociates at ~2300 C. The cracking of coolant water by overheated fuel elements would result in the generation of noncondensable gases (H2 and possibly O2) that would add to the pressure excursion. Venting is the only option at that point. This was an issue at TMI. The explosive concentration range of hydrogen is very wide.

IAEA goes on to say that Units 1,2,and 4 are experiencing increased pressure, but Unit 3 is in a safe cold shutdown condition.  Tokyo Electric Power Company received permission to inject boronated seawater into the Unit 1 reactor.

This is very ominous news. Plainly, if the cooling loops were dumping enough energy out of the reactor they would not inject corrosive sea water into it.

There is a lot of talk about a meltdown.  As of this post, nothing has been disclosed about the actual state of the Unit 1 reactor core.  There has been no word on the state of the fuel elements or the state of the coolant loops.  I assume that the reactor design has a negative reactivity coefficient that will attenuate the reactivity with water coolant loss or void space formation.  The link on reactivity coefficients delves into a number of interesting and perhaps not-so-intuitive effects on reactivity during an upset condition.