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The Seven Gods of Fortune

December 24, 2013
Gods of Fortune

The Seven Gods of Fortune

Over the last few months some our posts that have referred to the slow-motion, ongoing, multiple crises at the Fukushima-Daiichi nuclear power plant complex. A very brief overview of the event is provided at the post Two Too Many Common Causes. Some of our posts to date that are to do, at least in part, with the event include:

In spite of the importance of what has already happened and what could happen, particularly were there to be another large earthquake, there has been little public discussion as to what is going on at Fukushima-Daiichi. One reason for this may be that there have been fewer public reports than we saw with other major process safety events such as Piper Alpha, Texas City and Deepwater Horizon/Macondo. Indeed, the Japanese government recently passed a law that restricts investigative journalism into events such as Fukushima-Daiichi. (The Japan Federation of Bar Associations has expressed strong concern that the new law on state secrets may embolden the government’s propensity to hold back crucial information on nuclear safety (Ashahi Simbum)). The lack of reporting may also reflect the non-visual nature of the event. After the first few days, in which the earthquake and tsunami were followed by one or more hydrogen explosions, there has been little to see except for the construction of a large number of tanks to hold radioactive water. The dangers associated with radioactive releases are invisible.

Nevertheless, in spite of its low profile this event has the potential to be very serious indeed. Were there to be another earthquake or were one of the Reactor 4 fuel rods to be dropped or broken while being transferred the consequences could be such that large scale evacuation of the communities around the site would be required.

Process Safety Input

We have argued in previous posts, and continue to argue, that the situations is one that the process safety community should be following closely. Not only are there important lessons to be learned but it could be that process safety professionals may be able to make a contribution to the overall remediation process.

Seven Events

Gods-of-Fortune-2During the research for this post we came across the Japanese folklore of “The Seven Gods of Fortune”, also known as the Seven Lucky Gods. The image seemed appropriate for a discussion to do with Fukushima-Daiichi because there are actually seven scenarios at that site to need to be taken care of, and it seems as if good fortune will be needed to make sure that they are all handled properly.

The Fukushima-Daiichi complex consists of six nuclear reactors, all of a similar design. Units 1-4 were badly damaged by the Tōhoku subsea earthquake. Their backup power systems, which were at low elevation, were disabled by the tsunami that followed the the earthquake. Units 5-6 are newer and at a higher elevation and appear to have suffered less damage.

The seven events are:

  1. Presumed partial meltdown in Reactor 1;
  2. Presumed partial meltdown in Reactor 2;
  3. Presumed partial meltdown in Reactor 3;
  4. Removal of spent fuel from the Reactor 4 storage facility;
  5. Damage to Reactor 5;
  6. Damage to Reactor 6; and
  7. On-going flow of ground water through the complex and the integrity of the temporary water storage tanks.

Reactor 4

Fukushima Reactor 4

Figure 1

Most of the remediation work presently taking place is at Reactor 4. At the time of the earthquake it was out of service with its spent fuel rods in a water pool located directly above the reactor (not inside the reactor containment building). The explosions that followed the earthquake blew the roof off the building that contains the stored fuel rods (Figure 1).

The integrity of the building is questionable. Were it to collapse some of the fuel rods could be exposed to air. Given that these rods are cased in highly flammable zirconium they could catch fire and generate a plume containing large quantities of radioactive material. Therefore the facility operator, Tepco (Tokyo Electric Power Company), is currently moving the spent fuel rods from this building to a safer location. This operation is expected to take at least fifteen months and is itself hazardous. If any of the rods (many of which are already damaged) were to be dropped or broken they could also burn.

Reactor-4-4

Figure 2

A new building has been erected so that heavy equipment for the removal of fuel rods can be installed (Figure 2).

Diagram-1

Figure 3

In spite of the current focus on Reactor 4 it is likely that the long-term problems to do with Reactors 1-3 (Figure 3) are actually more serious. The cores appear to have melted down. They are still in the containment building, but eventually action will have to be taken. But entering these buildings will be a very hazardous enterprise. And deciding how to remove and dispose of the melted cores will be a challenge, to say the least.

Years and Years and Years

Three of the most striking features of these events have been

  1. The lack of Inherent Safety (Two Too Many Common Causes);
  2. The paucity of publicly available incident analyses; and
  3. The absence of a long-range emergency plan (The Two Second Rule).

A fourth feature is the amount of time (and money) that it is going to take to remediate the site. Even the relatively simple matter of moving the spent fuel rods from Reactor 4 to a safer location is estimated to take 15 months (and, given the extent of the damage to the building, it is sensible to assume that that estimate is on the optimistic side). But that time estimate pales in comparison with the years, and even decades, it is going to take to deal with Reactors 1, 2 and 3. And all the time the threat of another earthquake looms.

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