The American Kafir

2011/03/12

Nuclear Meltdown at Quake-Damaged Japanese Plant

Filed under: Nuclear — Tags: , , — - @ 9:53 am

Source Link: Stratfor

March 12, 2011 | 0827 GMT

North Korean Artillery Attack on a Southern Island

Footage of Fukushima Daiichi nuclear power plant

A March 12 explosion at the earthquake-damaged Fukushima Daiichi nuclear power plant in Okuma, Japan, appears to have caused a reactor meltdown.

The key piece of technology in a nuclear reactor is the control rods. Nuclear fuel generates neutrons; controlling the flow and production rate of these neutrons is what generates heat, and from the heat, electricity. Control rods absorb neutrons — the rods slide in and out of the fuel mass to regulate neutron emission, and with it, heat and electricity generation.

A meltdown occurs when the control rods fail to contain the neutron emission and the heat levels inside the reactor thus rise to a point that the fuel itself melts, generally temperatures in excess of 1,000 degrees Fahrenheit, causing uncontrolled radiation-generating reactions and making approaching the reactor incredibly hazardous. A meltdown does not necessarily mean a nuclear disaster. As long as the reactor core, which is specifically designed to contain high levels of heat, pressure and radiation, remains intact, the melted fuel can be dealt with. If the core breaches but the containment facility built around the core remains intact, the melted fuel can still be dealt with — typically entombed within specialized concrete — but the cost and difficulty of such containment increases exponentially.

However, the earthquake in Japan, in addition to damaging the ability of the control rods to regulate the fuel — and the reactor’s coolant system — appears to have damaged the containment facility, and the explosion almost certainly did. There have been reports of “white smoke,” perhaps burning concrete, coming from the scene of the explosion, indicating a containment breach and the almost certain escape of significant amounts of radiation.

At this point, events in Japan bear many similarities to the 1986 Chernobyl disaster. Reports indicate that up to 1.5 meters (4.9 feet) of the reactor fuel was exposed. The reactor fuel appears to have at least partially melted, and the subsequent explosion has shattered the walls and roof of the containment vessel — and likely the remaining useful parts of the control and coolant systems.

And so now the question is simple: Did the floor of the containment vessel crack? If not, the situation can still be salvaged by somehow re-containing the nuclear core. But if the floor has cracked, it is highly likely that the melting fuel will burn through the floor of the containment system and enter the ground. This has never happened before but has always been the nightmare scenario for a nuclear power event — in this scenario, containment goes from being merely dangerous, time consuming and expensive to nearly impossible.

Radiation exposure for the average individual is 620 millirems per year, split about evenly between manmade and natural sources. The firefighters who served at the Chernobyl plant were exposed to between 80,000 and 1.6 million millirems. The Nuclear Regulatory Commission estimates that exposure to 375,000 to 500,000 millirems would be sufficient to cause death within three months for half of those exposed. A 30-kilometer-radius (19 miles) no-go zone remains at Chernobyl to this day. Japan’s troubled reactor site is about 300 kilometers from Tokyo.

The latest report from the damaged power plant indicated that exposure rates outside the plant were at about 620 millirems per hour, though it is not clear whether that report came before or after the reactor’s containment structure exploded.

Japanese Reactor Container Breached

March 12, 2011 | 1804 GMT

As the crisis continues with Japan’s Fukushima Daiichi nuclear power plant, a variety of STRATFOR nuclear science and engineering sources said Japanese government statements that the troubled Unit 1 reactor container has not been breached are highly dubious. Reports of iodine and cesium outside of the plant indicate that the reactor’s containment structure has been breached.

Iodine is in the fuel pins and cesium is a particulate, meaning there are heavy particles in the air, which are basically radioactive dust. Selenium 137, which Yomiuri Shimbun reports has been discovered in the surrounding area, is probably a product of the nuclear fission process and a strong demonstration of severe damage to the nuclear reactor’s core. The fact that the government has prepared a series of iodine treatments for locals in the vicinity of the nuclear plants suggests it is anticipating the need to prevent iodine exposure.

Meanwhile 90 people were reported as possibly exposed to radiation, including 30 refugees from the area and 60 people on staff at Futaba hospital. Sources suspect that Japan has already undergone “clad failure” (when zirconium in the rods reacts with water) leading to a violent exothermic reaction. This produces large quantities of hydrogen. The March 12 blast was probably caused by a combined steam and hydrogen explosion. The explosion may have destroyed the containment structure in the reactor vessel. This raises the distinct possibility that the core will gain heat to the point that it will melt through the reactor at the bottom of the reactor vessel. While there remain too many uncertainties to make reliable forecasts, the disaster has clearly escalated to a high level. Critical questions will be whether the radiation count rises above 1000 millirems per hour and whether winds should change direction to blow radiation from the north into Tokyo.

March 12, 2011 | 0619 GMT
Japanese officials are cautioning that a nuclear meltdown may occur at the Fukushima Daiichi nuclear power plant near the town of Okuma. According to Japan’s Jiji Press, some of the reactor’s nuclear fuel rods were briefly exposed to the air after the reactor’s water levels dropped through evaporation. A fire engine is currently pumping water into the reactor and the water levels are recovering, according to an operator of the Tokyo Electric Power Co. (TEPCO), which operates the plant. A TEPCO spokesman said the company believes the reactor is not melting down or cracking and that workers are currently attempting to raise the water level.

If a meltdown takes place — essentially the core of the reactor overheating and damaging the fuel rods themselves — it would be the first since the Chernobyl disaster in 1986 and the Three Mile Island incident in 1979.

The Fukushima Daiichi power plant was shut down automatically on March 11 due to the magnitude 8.9 earthquake that hit Japan. The on-site diesel backup generators also shut down about an hour after the event, leaving the reactors without power and thus without the ability to cool down the core. Japanese officials were operating the cooling system via battery power and were flying in batteries by helicopter to keep the temperature regulated.

An unchecked rise in temperature could cause the core to essentially turn into a molten mass that could burn through the reactor vessel. This may lead to a release of an unchecked amount of radiation into the containment building that surrounds the reactor. This building could be breached if enough pressure builds, or, in this case, if the containment building was already breached through the earlier effects of the earthquake.

At the moment, it would appear that Japanese authorities are still trying to contain the reaction inside the reactor. That indicates that the core has not completely melted and that the reaction has not yet gotten out of hand. However, the situation could quickly become uncontrollable and the added water being pumped into the reactor could rapidly evaporate if the temperatures rise too quickly to be cooled off.

Explosion Reported at Japanese Nuclear Plant

March 12, 2011 | 0820 GMT

An explosion occurred March 12 at the Tokyo Electric Power Co.’s (TEPCO) Fukushima Daiichi nuclear power plant in Okuma, Japan, Japanese news agency Jiji reported, citing local police. Reports of an explosion and smoke come after Japanese officials cautioned that a nuclear meltdown was possible. Officials at the plant had reported that part of the reactor core was exposed to air for a brief moment and that they were attempting to raise the water level to continue cooling the reactor. Officials later stated that steam was vented from the power plant to release the pressure built up by evaporating water. If an explosion occurred, it would indicate that the additional water pumped into the reactor has been unable to stave off the meltdown reaction inside the reactor core and that the plant is experiencing a far more serious crisis than initially reported by the Japanese authorities.

Advertisements

Leave a Comment »

No comments yet.

RSS feed for comments on this post. TrackBack URI

Leave a Reply

Please log in using one of these methods to post your comment:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: