Six Ways Fukushima is Not Chernobyl | TPM LiveWire

Six Ways Fukushima is Not Chernobyl | TPM LiveWire

Six Ways Fukushima is Not Chernobyl

by Lois Beckett, Special to ProPublica

The crisis at Japan's Fukushima Daiichi has already been dubbed the worst nuclear accident since Chernobyl, and the situation there continues to worsen.

But along with references to the "ch-word," asone nonproliferation expert put it [1], experts have been quick to provide reasons why the Daiichi crisis will not be "the next Chernobyl."

Experts have noted several key differences in the design of the reactors in question, as well as in the government's reaction to the crisis:

1. Chernobyl's reactor had no containment structure.

The RBMK reactor at Chernobyl "was regarded as the workhorse of Soviet atomic energy, thrifty and reliable -- and safe enough to be built without an expensive containment building that would prevent the release of radiation in the event of a serious accident," The Guardian's Adam Higginbotham noted [2].

As a result, when a reactor exploded on April 26, 1986, the radioactive material inside went straight into the atmosphere [3].

Fukushima's reactors [4] are surrounded by steel-and-concrete containment structures [5]. However, as the New York Times reported Tuesday, the General Electric Mark 1 reactors at Fukushima have "a comparatively smaller and less expensive containment structure [6]" that has drawn criticism from American regulators. In a 1972 memo [7], a safety official suggested that the design presented serious risks and should be discontinued. One primary concern, the Times reported, was that in an incident of cooling failure -- the kind Fukushima's reactors are now undergoing -- the containment structures might burst, releasing the radioactive material they are supposed to keep in check.

At least one of Fukushima's reactors [4] -- No. 2 -- seems to have cracked, and has been releasing radioactive stream. The seriousness of this breach is still unclear [8], with a Japanese government official maintaining on Wednesday that the damage to the containment structure may not be severe.

2. Chernobyl's reactors had several design flaws that made the crisis harder to control. Most crucially, their cooling system had a "positive void coefficient," which means that as coolant water is lost or turns into steam, the reaction speeds up and becomes more intense [9], creating a vicious feedback loop.

Shan Nair [10], a nuclear safety expert who spent 20 years analyzing the consequences of Loss of Coolant Accidents like the one at Fukushima, discussed this factor on TIME's Econcentric blog [11]. Nair was a member of a panel that advised the European Commission on how to respond to Chernobyl. As he explained:

[Fukushima] can't be Chernobyl because the Boiling Water Reactors (BWRs) at Fukushima are designed differently than the High Power Channel-type Reactor (RBMK) reactor at Chernobyl. The RBMK was designed so that the hotter the core gets the greater the reactivity -- so you have a situation where you are in a vicious cycle and a race to an explosion. [Fukushima's] BWRs are designed in such a way that the hotter it gets the less radioactive the core gets so there is a self-shutdown type of mechanism. But the problem is that before you can get to a safe level you might have a complete meltdown. I believe that's what they are battling against now in Japan.

3. The carbon in Chernobyl's reactor fueled a fire that spewed radioactive material further into the atmosphere. Fukushima's reactors do not contain carbon, which means that the contamination from an explosion would remain more localized.

Dr. Colin Brown, director of engineering for the UK-based Institution of Mechanical Engineers [12], described another of the Chernobyl reaction's design flaws in a post on the Institution's website [13]explaining why it was "unlikely" that Fukushima "will turn into the next great Chernobyl with radiation spread over a big area." He wrote:

The reason why radiation was disseminated so widely from Chernobyl with such devastating effects was a carbon [graphite] fire. Some 1,200 tonnes of carbon were in the reactor at Chernobyl and this caused the fire which projected radioactive material up into the upper atmosphere causing it to be carried across most of Europe. There is no carbon in the reactors at Fukushima, and this means that even if a large amount of radioactive material were to leak from the plant, it would only affect the local area.

Britain's Chief Scientific Officer, Sir John Beddington [14], made a similar point about the localized nature of an explosion in a speech about Fukushima on Tuesday [15]:.......