It’s Thursday morning here and Thursday evening in Japan. It’s been a frustrating day for crews trying to contain the radiation dangers at the crippled Fukushima Daiichi Nuclear Station.
Earlier hopes that restoring offsite power to the control rooms at Units 1-2 and 3-4 would allow quick reactivation of normal cooling systems were dashed with discovery, anticipated in our coverage, that critical pumps, valves and pressure sensors might be damaged and need repair or replacement.
And as radiation continued to spread from the reactors, officials found unacceptable levels of radiation in tap water as far as Tokyo and continuing unacceptable levels in produce and milk in the prefectures surrounding the Fukushima Daiichi. It’s now clear that the evacuation and stay indoors areas will be expanded from the current 20 and 30 kilometer circles respectively.
But if you want a flavor of the nightmare they’re still facing, consider the New York Times story about the man on the ladder. But first, a little history.
More than 30 years ago, a still young counsel at the California Energy Commission was assigned the task or drafting the Commission’s first decisional document, a preliminary assessment of critical safety features at a proposed nuclear plant that was applying for a state construction license in California. Most of the assignment was just learning about how a nuke functions and how it’s safety features would function during normal and emergency conditions.
So, I got immersed in reports and testimony on “defense in depth,” the nuclear industries talking point invented to assure the public that no matter what happened, there was always a another backup safety mechanism that avoid a catastrophe. I vaguely remember the witnesses talking about the cladding, and the boron-filled control rods, and the integrity of the pressure vessel, the multiple containment structures, emergency cooling systems, back-up generation on so on. But I’m quite certain the one thing the witnesses never mentioned was the poor guy on the ladder. My report never mentioned him.
Yesterday, the New York Time’s described the situation inside the crippled Daiichi Units, even after they restored power to the control rooms and could start testing gauges and controls. Debris and damaged equipment from the explosion could be everywhere. And before they could even attempt to restart the cooling pumps, they had to be certain all the valves were in the correct open/closed position.
But much of the equipment could have been rendered inoperable from salt corrosion and build up, coming from continuing injects of sea water into the emergency cooling systems. Since some of the valves might be stuck, or the power to them inoperable, a plant worker might have to manually close or open a valve or two. From the Times: (my bold)
The emergency cooling system pump and motor for a boiling-water reactor are roughly the size and height of a compact hatchback car standing on its back bumper. The powerful system has the capacity to propel thousands of gallons of water a minute throughout a reactor pressure vessel and storage pool. But that very power can also be the system’s Achilles’ heel.
The pump and piping are designed to be kept full of water. But they tend to leak and develop alternating pockets of air and water, Mr. Friedlander said.
If the pump is turned on without venting the air and draining the water, the water from the pump would hit the alternating pockets with enough force to blow holes in the piping. Venting the air and draining the water requires a technician to reach a dozen valves, sometimes using a ladder. The water is removed through a hose to the nearest drain, usually in the floor, that leads to machinery designed to remove radiation from the water.
The process takes a full 12 hours in a reactor that is operating normally, Mr. Friedlander said. But even then, the water in the pipes tends to be radioactively contaminated because the valves that separate it from the reactor are not entirely tight.
[cont’d.]So, some very brave soul, possibly one of the already exposed Fukushima Fifty, will have to walk inside the reactor building, withstand the internal radiactivity, seek out the damaged valves, remove the debris, climb up a latter and manually open or close the valves at just the right moment. Defense in depth.
That same article contains a better description of the damaging toll the use of sea water will have on safety equipment, possibly rendering much of it inoperable unless the salt build up can be quickly and safely flushed from system with massive injections of purified fresh water, which will come from . . . where? If they had that already, they would have used it.
So if I’m ever in a position again (unlikely) to have to write a safety assessment, I need to remember to add to the list of “defense in depth” features the following items: Water flushing system, debris remover, extra strength hazmat suits, a ladder, and one very brave worker. Oh, and millions of gallons of bottled water for the neighbors. I’ll keep the list open.
We’ll add some actual details as updates come in. Thanks again to all commenters who have helped in this effort.