I’m no expert, but it may make sense to evaporate rather than purify our way toward a reduced bulk of heavily contaminated water.
TEPCO set up a water-purifying rig and had planned to replace the filters about once a month, based on expected radiation levels. About a week ago, they fired it up and five hours later, they shut it down with filters at 110% of the limit. Perhaps purifying the water is not an appropriate measure right now.
Here’s an overview of my proposal: Take hot water from containment and flash it with a mild vacuum. Draw off the fairly clean steam, and condense it elsewhere. Return the remainder to containment. This reduces the bulk of heavily contaminated water while slightly increasing its concentration. Add clean cool water directly to the containment, which cools containment and mostly restores the contamination level.
If successful, this process will intake clean cool water and exhaust mostly clean hot water, while cooling containment, not increasing the volume of stored heavily contaminated water, and not directly addressing decontamination. If this can be accomplished, it creates a lot of working time to better address the decontamination problem.
As more evaps can be brought on-site and placed in service, (assuming that it will take “several”) the accumulation of heavily contaminated water should slow and perhaps stop.
[pullquote]five hours later, they shut it down with filters at 110% of the limit[/pullquote]
Eventually, the water must be purified, but the proximate threat (severity * likelihood) seems to be that the volume of heavily contaminated water is increasing more rapidly than storage resources can be brought to bear. There are two connected issues with the cooling water. One is that it becomes contaminated, and the other is that it becomes hot. The only reason the volume of water is growing is that our only means of solving the heat problem is dilution of hot water by adding cool water, which causes the follow-on issue of increasing volume.
Obviously, there are many barriers to successfully implementing *any* solutions to this problem, so don’t get hung up on details (who will drive the truck, etc). I just want to vet a concept.
Current water input totals about 20 cubic meters per hour (4.0 in Unit 1, 4.5 in Unit 2, 10.0 in Unit 3), or about 1,000 cubic meters every two days. I assume two things; that this is the volume of water depleted by leakage, evaporation, and withdrawal of hot water to make room for cool water, and that this rate of mass flow is balanced against the requirements of temperature. If an evaporator only gets (conservatively), say 5% water removal, then we need to process 20x that amount, so 400 cubic meters per hour flowing (from all units combined) into our evaps, and 380 returning. (At 264 gal/Cu. m, that’s 1,760 gallons per minute minus 264 gallons per minute). Important to keep in mind, however, that we are not constrained to keep up with an input rate so much as the input rate and the percent water removal must result in 20 cubic meters of water removal per hour.
Here’s a transportable evaporator which is specified as “2,200 liters/hour” (bottom of the list). I hope that’s evaporation throughput, not feed–I don’t know, but I can’t imagine specifying feed instead of water removed. We would require about 10 of these continuously online to break even on the current cooling water requirement.
Here’s one (Whoops, will fix the link) for 9,000 l/h, (actually, 9,000 kg/h, but close enough) of “water removal”, which is indeed what we want to know. 20 cubic meters (per hour) is 20,000 liters, so we would need three of these in continuous operation.
There’s an assumption here, which is that “9,000 kg/h of water removal” is from a much larger stream of feedwater. If this thing instead is intended to operate on 10,000 kg of water sitting in a pan for an hour, then this doesn’t work. More to follow.
