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.
Update I, 1:30 pm EDT: Watching NHK TV English feed indicates the coverage has shifted strongly from containment activities at the plant sites (it’s 2:30 a.m. Friday there) and to increasing public and official concern about the dispersion of radiation and its possible health effects. Lots of stories of citizens worried about the tap water, about their children, with many parents having already used tap water for bathing and cooking before they got the warnings.
Maps showing locations of higher readings go well outside the 30 km stay indoors radius and as far south at Tokyo, 140 miles away. Key point: increased radiation doesn’t spread uniformly out from the plant. Rather it is driven by wind direction and speed and weather. So we get increased readings south of the plant on one day, which falls the next day, but increased readings east and northeast the next day, as wind direction changes. Further, rain in one area can increase radiation readings there by bringing more of the airborne radiation to earth, even though it’s further away from the site than areas with lower readings nearer the plant. So the patterns of dispersion are highly variable and difficult to model for predictive purposes. But they’re now dealing with increased radiation in the air, on the ground and produce, in water supplies at many locations and in the ocean, while trying to prevent panic. [It appears the Tokyo tap water warnings ended on Thursday.]
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. With radioactive smoke still coming from Unit 3, three more workers (laying electrical cables) at the site were exposed to dangerous levels in excess water outside, two of them hospitalized.
And as radiation continued to spread from the reactors, officials found unacceptable levels of radiation in tap water as far as Toyko and continuing unacceptable levels in produce and milk in the prefectures surrounding the Fukushima Daiichi reactors. It’s now clear that the evacuation and stay indoors areas should be expanded from the current 20 and 30 kilometer circles respectively, and they’re losing time to carry that out.
But if you want a flavor of the nightmare they’re still facing, consider yesterday’s New York Times story about the the salt buildup, stuck valves and the man on the ladder. First, a little history.
More than 30 years ago, I was a counsel at the California Energy Commission assigned the task of 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. Much of the assignment was just learning about and explaining how a nuke functions and how its safety features should work during normal and emergency conditions.
So I got emersed in reading reports and testimony on “defense in depth,” the nuclear industry’s talking point invented to assure the public that no matter what happened, there was always another backup safety mechanism that would avoid a catastrophe. I vaguely remember the witnesses talking about the cladding, and the boron-filled control rods (to absorb neutrons and stop/slow the reaction), and the integrity of the reactor vessel, the multiple containment structures, emergency cooling systems, back-up generation and 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 Times 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 know water levels and be certain all the valves on the water cooling system 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 10 days of injecting 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 the stuck valves. Now, it’s not unusual for plant workers to manually open/close valves. They just normally don’t do this under such dangerous conditions. 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.
So, some very brave soul, possibly one of the already exposed Fukushima Fifty, will have to walk around inside the reactor building, withstand the internal radiactivity, seek out the damaged valves, remove the debris, climb up a ladder 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 is likely having on safety equipment, possibly rendering much of it inoperable unless the salt buildup can be quickly and safely flushed from the cooling system using massive injections of purified fresh water. That pure water will come from . . . where? If they had enough of 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, garden hoses, debris remover, extra strength hazmat suits, an undamaged ladder or two, and at least one very brave worker. Also, better boots for the guys laying the power lines outside. Oh, and millions of gallons of bottled water and relief food supplies for the neighbors in a 50 mile or so radius while they wait to see if this works. 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.
NHK live tv feed
New York Times coverage has generally been very good, especially from Matt Wald, a 30-year veteran of nuclear/energy reporting, who was part of a media coverage panel I saw at Harvard’s Kennedy School yesterday. Bottom line: Mixed bag: lots of misinformation, some scaremongering and confusion (tv first showed harmless cooling towers instead of reactors); governments often don’t understand what’s happening, even if they’re honest, which they aren’t. Where have you gone, Harold Denton? The Harvard expert who’s co-principal investigator of nuclear studies isn’t sure what info the US had when they second guessed Japanese officials last week. Matt Wald’s latest is here.
Picture of Unit 1 control room, via Kyodo News
Nuclear Power Plant Primer — good expert video