Since yesterday’s update, very little progress has been made in the effort to restore power throughout the Unit 1 through Unit 4 power complex. TEPCO reports do, however, let us know something that has puzzled this writer for a few days. While there may have been enough steam from the reactor to run the steam powered feedwater pumps for several days, the temperatures inside the reactors for the past several days have been way too low to make steam powered pumping possible. How was the water being “injected” since the reactor temperatures dropped? Today, TEPCO reported that the pumping of water into Unit #3 reactor was switched from firetruck pumps to a temporary electrical pump. All three reactors were at ~ above 300 degrees C when the “injections” first started, a temperature that means the pressures must have been above the 1000 psi range (saturation temperature/pressure relationship, for you techies). Can fire truck pumps work against these pressures? It seems they can. Most high pressure fire pumps can move water at pressures up to nearly 1500 psi, and some even higher, however the amount of water moved would be very low…below 10 gallons every minute. However, once the reactor pressures dropped along with the temperature drops due to cooling water being injected, the fire truck pumps could work better and the flows of water increase considerably. Further, at the pressures that have been the case for the past few days inside reactors 2 & 3 (essentially just above atmospheric), the fire truck pumps would pump a lot of water, rather quickly. Reactor #1 pressure seems to be in the 500 psi range, however, suggesting that the combination of steam turbine and fire truck pumping is still the case. So, it seems the fire truck pumps have been injecting water into all three reactors for several days, if not longer. So why hasn’t TEPCO told us this? Why does it have to be deduced from press release analysis? <groan>
On another note, it now seems that the replenishment water being injected into the slowly evaporating spent fuel pools is being pumped through the fuel pool cooling and filtering (cleaning) system’s pipes, but the actual pumping is through temporary pumps. Firetruck pumps could do this quite easily for they would not be trying to pump against huge pressures. The lower the pressure the truck pumps have to work against, the higher the rates of flow. But, I can find nothing about the types of pumps being used in the TEPCO press statements. Another oversight by TEPCO?
On a related note, Emailer “Pascal” (who’s in Japan…my bad, Pascal) linked me to a German visual/graphic presentation on the sequence of events at Fukushima. (ref. below) Some of the information is purely speculative concerning the amount of fuel damage which is allegedly the case in the three Fukushima reactors. The creator of the presentation references Japan Atomic Industrial Forum speculations on fuel damage, which assumes a lot of uranium and zirconium melting…50% or more in reactor #2, for example. I think it’s overly pessimistic, but that’s merely my personal opinion.
However, Dr. Matthias Braun, who put it together, makes a stunning statement on the water level issue relative to the 4 spent fuel pools. He states it would take pool number four, which certainly has the most decay heat production, ten days to boil dry. Unit 4’s spray-replenishment efforts began on March 17, barely six days after the tsunami. Not nearly enough time for a dry fuel pool. In fact, probably not enough time to uncover the tops of the fuel cells. The pools are ~11 meters deep, with the 3.6 meter tall fuel cells at the bottom. This leaves 7 meters of water on top of the fuel. A quick use of the calculator using Braun’s numbers, and we find six days of evaporation would drop water level about 6.5 meters, still leaving half a meter (1½ feet) of water above the fuel. Could earthquake sloshing have tossed that much water (60 tonnes) out of the pool? And, would not most, if not all of the water sloshed out have returned to the pool due to gravity after the shaking stopped? The plot thickens…
Emailer “Ronald” is also to be commended for doing a wonderful job keeping me abreast of the American news media spin-meisters, since I’m avoiding that rhetorical snake-pit as much as possible. You’re a better man than I, Gunga Din! Seriously, I’m glad he’s doing this. Last evening, he alerted me to how the American cable news channels were broadcasting that Plutonium had been detected coming from Fukushima, and this means meltdown and a reactor vessel leak. I immediately linked up to IAEA, Asahi Shimbun, Kyodo news, NHK (Japan’s CNN), and TEPCO press release sites.
It turns out, five soil samples taken on the TEPCO property at Fukushima were found to have a trace of Plutonium in them. This probably came from Unit #3 which uses Mixed-Oxide fuel for the reactor. In everyday language, recycled nuclear fuel. 95% of the spent fuel is perfectly good for re-use, and 5% is fission by-products. Recycling (reprocessing) removes the by-product elements, and what you have left is about 99% Uranium isotope 238 (U-238) and 1% Plutonium (three isotopes, we’ll soon get to). This is good fuel for reactors. Mix it with near-natural Uranium, form it in new fuel pellets, and put it back in the fuel cycle. Yes, power plant fuel is eminently recyclable.
With that in mind, we can now look at the next item in the Plutonium reports coming from Japan. The concentration of Plutonium in the soil samples is about the same as the amount of Plutonium found with many places in Japan due to American, Russian and French atmospheric bomb testing in the 1950s. Not much, but the question immediately arises as to how can the two sources be distinguished from each other? Might not the Fukushima Plutonium be from the old bomb tests, and not from Reactor #3? Actually, for a nuclear laboratory analyst, making the distinction is quite simple. Bomb Plutonium is only one isotope, Pu-239. It’s peak on a graphic read-out is unique to it’s elemental/isotopic mass number Pu-239. Reactor Plutonium is about two-thirds Pu-239, one-third Pu-240, and about a percent or two of Pu-238. Each of these have a graphic peak unique to each respective isotope (Pu-238 and Pu-240). With Bomb Plutonium, we get only the Pu-239 peak. With reactor Plutonium we get all three peaks. The soil samples at Fukushima have all three peaks. It’s from Fukushima, and probably Reactor #3.
Does this mean Reactor #3s fuel cell is melting down? Probably not. There’s no doubt there’s been at least high enough temperatures inside reactor #3 during the first 4 days after the tsunami to cause the Zirconium cladding around the fuel pins to crack, pit, and generally deteriorate due to metallic oxidation and the generation of hydrogen. Yes, the Zirconium alloy tubes hold the fuel pins in place, but they also provide a very good barrier preventing the fission by-products on the surface of the fuel pins from escaping into the boiling water inside this Boiling Water Reactor’s fuel cell. The heat damage to the Zirconium inside reactor #3 is undoubtedly extreme, including possibly some localized Zirconium meltage. The amount of fission product material released must have been terrific, even if there was no Uranium melting (which no one should speculate on, at this point). Plus, at the elevated core temperatures needed for Zirconium heat damage, the fuel pins inside the tubes would have swelled a tiny bit, increasing the surface area on the outside of the pins which would further exacerbate the expunging of fission products. Could this account for all the contamination found in the Unit #3 basement and/or it’s external drainage trench? No. But, throw in the neutron activation levels we can now understand to also be in the contaminated water mix, and it all seems possible.
Does the discovery of Plutonium on-site mean reactor #3 is having a meltdown? If it did have a meltdown, it would have happened more than 10 days ago, before cooling water injections began. Now now. Then where did the Plutonium come from? The pathway scenario identified days ago…reactor pressure relief valves dumping contaminated steam into the suppressing water volume in the torus. The torus eventually gets to a high enough pressure for it’s pressure relief valves to open, releasing it’s highly-contaminated steam to the secondary containment. From there, due to voluminous sprayings upon the thick layer of debris covering the refueling deck, mixing of the reactor isotopes with the fuel pool isotopes gives us a highly-concentrated contamination “soup”.
Is the reactor vessel leaking? As long as the temperature inside the Unit 3 reactor is below the boiling point, and the internal pressure steadily remains slightly above atmospheric, there is no hard evidence to say the reactor vessel is leaking. Rather, the pressure and temperature read-outs for the Unit #3 reactor indicate no leak from the vessel. Water level readouts are variable on Boiling Water Reactors because of the steam mixing with the boiling water. The other two parameters are a much better indicator of vessel integrity. Further, if there were a vessel leak, the pressures and temperatures inside the primary containment of Unit #3 would be increasing, which doesn’t seem to be the case. [Nuclear and Industrial Safety Agency (NISA) data] Finally, if #3 reactor is leaking, why is it’s primary containment pressure half the level of pressure in Unit #1? Should be the other way around, if there’s a vessel leak from Unit #3. There have been no speculations of Unit #1’s reactor leaking, so why speculate on reactor#1’s condition?
Braun, Dr. Matthias; “The Fukushima Daiichi Incident”; March 27, 2011; http://passworld.co.jp/ForumImages/2011/03/29/Fukushima.pdf; Pg. 32