Spent nuclear fuel pools: emergency triage and prioritization

In the weeks and months following the meltdowns of March 2011 at the Fukushima-Daiichi nuclear plant, Japanese emergency personnel spent a huge amount of time worrying about the condition of the pools that hold used nuclear fuel. That became a major issue in the global public conversation about the events. Doomsday scenarios were trotted out, in which the zirconium cladding around the fuel catches fire as it reacts with air. The whole assembly then explodes, lofting radioactive fission products into the air; they all fall to the ground on Tokyo. Pure comic-book nonsense, but widely recycled through the mainstream media and taken up by panicky politicians. As it turns out, there was not much to worry about. Water hadn’t drained out, and the fuel assemblies were not exposed to air. Even if they had been, the doomsday scenarios could not have come to pass. Will Davis, writing at the ANS Nuclear Cafe, did an excellent job of debunking a few of the more persistent fantasies purveyed by anti-nuclear lobbyists with over-active imaginations.

The problem was, not enough was known of the actual conditions of the pools in the aftermath of the meltdowns. The emergency crews at Fukushima could not say with certainty that the pools’ physical integrity was sound. They therefore spent a lot of time preparing for the worst. That time could have been far more productively spent doing more important things.

Recognizing this, nuclear regulators around the world have ordered power plants to implement some kind of monitoring system that can withstand severe events and reliably tell what the water level is. The French nuclear company Areva has come up with a two-pronged instrumentation approach to monitoring water level:

  1. An air-radar system reads microwave signals that bounce off the surface of water in the pool and can tell from any differences in the time from “send” to “receive” whether water level has changed.
  2. A pressure transducer immersed in the pool at the level of the fuel elements detects changes in water pressure that would indicate an increase or decrease in the pool water level.

These systems are independent, and based on totally different physical principles. Therefore, says Areva, the possibility of common-mode failure is eliminated, and the utility can be assured that it knows the condition of its spent fuel pools.

I spoke with the Areva sales contact for this system, Heiner Dornburg, this morning via teleconference. I asked if he’s pitching this system to Canadian utilities. His answer was of course, all nuclear regulators have required some kind of spent fuel pool integrity monitoring rule in the wake of Fukushima.

I also asked if Areva is still interested in selling its 1,650-megawatt EPR to Ontario. Areva was in the thick of the 2009 RFP in Ontario, but all the public indications have been that today the two contenders for new-build at Darlington are Westinghouse and CANDU. The answer was a bit less definite. Basically, they’ll get back to me.

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