The plot thickens…
Reports out of Japan since Monday have revealed a number of disturbing items. Remarkably, the most recent reports concerning the events at Fukushima Daiichi, March 11 through March 16, suggest that several of this writer’s previous conjectures were correct (in italics).
- TEPCO information, through the Japanese Atomic Industrial Forum (JAIF), indicates that meltdowns occurred in all three fuel cores of Units #1, 2 & 3, with the worst degree of damage in RPV #3’s core.
- Asahi Shimbun says the hydrogen explosion on #4 refueling deck came from Unit #3 core, which had the worst of the three meltdowns and produced the highest volume of hydrogen.
- Kyodo News reports Unit #2’s delay in venting was because two initial attempts to vent failed. The operators did not vent earlier because they couldnot. Further, the delayed water injection to #2 RPV was due to the inability to reduce pressure enough for pumping to work. This unavoidable delay, plus damage to the Unit #2 refueling deck due to flying chunks of concrete from the Unit #3 explosion which allowed some of the hydrogen buildup to escape, avoiding a Unit #2 hydrogen explosion.
*This writer is not omniscient, of course. Asahi Shimbun reports that all three reactor cores experienced severe, if not full meltdowns during the first few days of the accident. I have surmised damage to Unit #2 to be much less than the other two fuel cores, and that now appears to have been correct. Unit #3 is the worst, without a doubt, with Units 1 being second-worst, and unit #2 the least-worst.)
The reasons behind the nearly two month delay in reporting the above items is disturbing. It now seems that Monday’s Asahi Shimbun article alleging TEPCO concealing early-on radiation data, may be the virtual tip of the concealment iceberg. Important items of information were known to TEPCO and the government during the first days of the emergency, but have been withheld until now. Both should be held accountable for what now seems to have been an intentional act.
- JAIF reports operators of Unit #1 manually shut off the automatically-initiated flow of cooling water to the core 10 minutes after the earthquake, because of an unexpected pressure drop inside the RPV. Cooling water flow remained shut off for three hours. No wonder Unit #1 melted first. Decay heat production is massive for the first hour after reactor fissioning ceases (SCRAM), and remains high for several hours after that. This is a gross example of operator error. Never, ever should emergency cooling water flow be stopped…not for any reason! (Operator records show that this report was totally incorrect)
- Asahi Shimbun reports that all three RPVs experienced sharp pressure drops, many hours before venting began from each system. It appears that instrumentation penetrations through the RPVs failed first. Instrument penetrations are acknowledged as the weakest points on the RPV. However, they are quite small in size. Such failures of instrumentation penetrations would cause a rapid initial drop in pressure, but not a complete loss of pressure, as was the case in all 3 RPVs. A complete loss of pressure would be an indication of a larger pipe or control rod drive mechanism (CRDM) shearing off, literally draining the RPV in rapid fashion. This did not happen. Yet, the failure of an instrument penetration would be sufficient to lower water levels, albeit slowly, if there were no cooling water flow to replenish the level. This seems to have been the case with Unit #1.Some news media outlets have reported that Unit #1 meltdown began during the 3 hours of no cooling water flow to RPV #1, because water level was lost through a leak. Highly unlikely. The leak definitely lowered water level slowly, but would not have uncovered the core long enough to initiate meltdown before the water flow was restarted by operators. Fuel meltage begins at more than 2,800 oC (~5,100 oF). Yes, the fuel was overheated severely during the three hours of cooling flow shut off and generated hydrogen, but it is unlikely the fuel reached the melting temperature. This writer continues to believe that the onset of severe melting occurred after venting began on March 12.
- Asahi also reports Haruki Madarame, chairman of Japan’s Nuclear Safety Commission, said that the meltdowns should not come as a surprise. “When highly contaminated water was found at the No. 2 reactor building in late March, we recognized that a meltdown had taken place. So I informed the government,” he said. “As for No. 1 and No. 3 reactors, we recognized that, given the processes that led to the accidents there, the same thing had occurred.”So, why didn’t Prime Minister Kan’s government tell us about this in March? It seems the concealment issue extends to the government as well.
- JAIF reports power generation trucks were brought to the Fukushima power complex within 24 hours of the complete loss of power. The first attempted hook up was to Unit #2 switchboard, and some power was sent into the system for a short time until the Unit #1 hydrogen explosion, which “fried” the connection. Two days later, a second hookup with Unit #2 was about to be completed when concrete chunks from #3 hydrogen explosion destroyed the truck. (At least they tried! They should have told us.)
- JAIF also reports that the back-up batteries for Units #2 & 3 were “engulfed” by the tsunami and shorted out. They were completely useless thereafter.
- Asahi Shimbun contends that during the first week of the emergency many “experts” in Japan said one or more meltdowns occurred , but niether TEPCO nor the government would confirm. Instead, they downplayed the possible extent of damage to the cores and proceeded on that false assumption.
- It now seems that the physical integrity of RPV penetrations larger than instrumentation lines were compromised for a time on each Unit, and TEPCO had more than enough evidence to tell us upon discovery of the turbine basement waters. For Unit #3, this may have included one or more of the CRDMs through the bottom of the RPV. Speculation now exists that some of the fully melted core (corium) from Unit #3 fuel cell may have broken through the CRDM housing (or housings) and fell to the concrete floor beneath. The base mat below the RPV is ~ 10 feet thick, made of high-density steel-reinforced concrete. Even a full corium breach to the floor wouldn’t get more than a few inches into the base mat before cooling and solidifying. Regardless, the leaked corium would have cooled and solidified almost immediately upon contact with the floor.
- This morning, NISA ordered a full disclosure of all information concerning the first week of the emergency, specific to the reasons for all accident-related events at the facility, both inside (leading to fuel damage) and outside (loss of all electrical supplies). What else will we find out?
Now for some good news….
- All three cores are thousands of degrees below fuel melting temperature, so the large volumes of corium that dropped into the RPV bottom heads have cooled and solidified. This means any bottom head breaches sealed early-on, and have been closed for two months! Thus, any continuing leaks from the RPVs must be higher up, through wall penetrations.
- RPV #1 temperatures at the bottom head and feedwater nozzle high above the head, are both below the 95 oC criteria for “cold shutdown” conditions. The unsteady nature of plant conditions, however, make a cold shutdown declaration imprudent, to say the least.
- Core temperatures for Units #2 & 3 continue to decrease. It makes no sense to continue reporting RPV pressures since the new revelations make it unlikely the pressure detectors survived the intense heat.