Fukushima’s Cold Shutdown Condition

“I just checked in to see what condition my condition is in.”

One of the truly scary but perversely enjoyable characteristics of nuclear developers is their penchant for making it up as they go along – and then creating new Nukespeak words and concepts to describe what they’re up to as they do.

The latest example concerns the situation at Japan’s still-dangerous Fukushima Daiichi plant and comes to us via the Nuclear Energy Institute and its “Ask an Expert” question-and-answer page:

Question: What is “cold shutdown?”

The U.S. Nuclear Regulatory Commission says it is “the term used to define a reactor coolant system at atmospheric pressure and at a temperature below 200 degrees Fahrenheit following a reactor cooldown.”

“In non-nuclear speak,” the NEI’s anonymous expert helpfully explains, “it basically means the conditions within the nuclear reactor are such that it would be impossible for a chain reaction to occur.

Of late, news outlets have reported that Fukushima Daiichi may be in “cold shutdown” as soon as sometime this month. In actuality, however, as the NEI notes, “there is a difference between the traditional ‘cold shutdown’ of a nuclear plant and what is happening at Fukushima.”

When a reactor is in cold shutdown, the reactor pressure vessel (RPV) can be opened to add water to the cavity above it as a shield during either refueling or defueling. But at Fukushima Daiichi, cold shutdown is not been possible since the RPVs have been breached and will not hold water. Moreover, we now know that at least some melted fuel escaped, coming to within one foot of escaping primary containment on the floor below.

 So there can and will be no cold shutdown of the Fukushima plant. Realizing that it was impossible, beleaguered utility executives at TEPCO, the plant operator, “developed a new term, cold shutdown condition,” the NEI reports.

Here’s how TEPCO defines it: “Temperature of RPV bottom is, in general, below 100 degrees Celsius. Release of radioactive materials from PCV is under control and public radiation exposure by additional release is being significantly held down.”

By this definition, the Fukushima Daiichi reactors will reach cold shutdown condition soon – “once they are below boiling point and are no longer releasing significant amounts of radiation into the atmosphere.”

Do you suppose this newly defined condition at Fukushima has anything to do with the fact that reaching cold shutdown at Fukushima Daiichi is impossible – but that TEPCO expects to reach the newly created cold shutdown condition by the end of the year?


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