Progress is Normal
Progress in restoring normal cooling to units 1, 2, and 3 are progressing normally. Meanwhile the portable seawater pumps are doing their jobs and cooling the three reactor. The combination of fire trucks and a robot have been applying water to the #4 spent fuel pit in adequate quantities. Electric power should be restored to unit 2 by the time I publish this.
Meanwhile the cores have a week of decay time on them. They’re producing maybe 1% of the heat produced right after shutdown. Because of this decay, as each day passes the cooling job gets easier and easier.
Unit 4 Spent Fuel Pit
It looks like adequate cooling has been restored with the aid of fire pumpers, water canon and a robot. It also looks like some of the freshest fuel in the pit has failed. That is, the cladding has melted/burned away exposing the fuel pellets. It is very unlikely that fuel that old could generate enough heat to melt the pellets so what likely exists in that part of the pit is a TMI-like rubble bed of pellets and parts of pellets (they’re ceramic so they break when quenched with water after getting very hot).
Hard numbers are almost impossible to come by but World Nuclear News  is reporting that about 40 R/hr was reported on the inland side of unit 3 and 10 R/hr on the inland side of Unit 4. These are high numbers relative to the human exposure limits. They didn’t date the measurements but I would assume they were taken some time today.
Several things to be careful of when interpreting these readings. Location is everything. The explosion could have flung outÂ small particles of spent fuel. If the technician making the measurements walked around looking for the highest reading (a natural thing to do) then as he got nearer a particle the “ambient” reading would go up, up, up.
In my opinion it is unlikely that a uniform radiation field of that magnitude exists in the area. Think of a flashlight laying on the ground shining a light up in the air. In the beam the light intensity is high. All around it is dark.
Some degree of that dose is probably due to skyshine. Gamma rays emitted upward from the spent fuel pit are scattered just like light rays are. This causes the same kind of skyshine that in the optical spectrum bugs astronomers from street lights. That skyshine will decrease rapidly with distance from the pool. When water level is restored, that will go away.
Since there is failed fuel in the pond, there is probably also a noble gas element to the dose. Xe-133 has been through a half-life now so its contribution, while still high, has decreased significantly and will continue to do so. I imagine that the gas has filled the spent fuel pit and is flowing over and down the sides and hanging around the ground.
Some gamma spectrometry data would clear this up authoritatively but that’s not been forthcoming even though I know the data is being acquired. Too bad the utility or the IAEA hasn’t set up a single clearinghouse of raw data for us to interpret.
With the reporting of “contaminated food” inland of the plant, I have to comment about the techniques used for scare mongering. I will do so by analogy.
Let’s consider a 5 gallon bucket. That bucket represents the amount of radiation a person can absorb without harm. Let’s let water represent radiation.
If I put a single drop of water in the bottom of the bucket, I can truthfully but deceptively say that “radiation (water) has been detected in the bucket”. If I add another drop, I can truthfully but deceptively say that “radiation (water) level in the bucket have doubled”. If I put several drops in the bucket and then stand back and allow them to evaporate (decay), I can truthfully but deceptively say that “Radiation (water) levels were high but are slowly decreasing”.
Unfortunately our radiation detection technology plays into that. We have instruments that can detect single gamma photons and single atoms undergoing radioactive decay. This is the most sensitive measurement of any phenomena.
The other scare tactic is to report that the radiation is “thousands of times above normal”. The main problem there is defining normal. Normal background radiation levels vary several orders of magnitude, from 5-10 micro R in areas far away from granite or uranium or thorium bearing sand to 5 or 6 MILLI R on the black sand beaches of Tripoli, Libya. The latter is due to the high thorium content. Were those beaches located inside a nuclear facility, they’d be roped off as radiation areas with controlled access.
So like the saying goes, “nothing plus nothing still equals nothing.”. The media and the anti-nuke crowd intentionally use that language to sow fear and doubt. They use those techniques even when the real hard numbers are available.
Since things have stabilized at the plants, I probably won’t be doing daily updates. I will write when I see something reported that needs interpretation or expansion upon. Like the cop says, “Everything’s over. Y’all can go back about your normal business.”