Each day that passes reveals more details with the sequence of events leading to the meltdowns at Fukushima units #1, 2 & 3. Further, world-wide meltdown reports vary from source to source, which indicates considerable confusion over the revealed data. It is not merely a translation problem. Nearly all Japanese news sources also seem confused. Of the bunch, NHK News seems to get it right more often than the rest. In addition, TEPCO seems to have a penchant for leaving itself open to extreme speculation, which nearly all news media voraciously feed off of. Who should we believe? From our perspective, one information source has best stood the test of time through-out the emergency; Japan’s Atomic Industrial Forum (JAIF).
- Tuesday morning, JAIF and several Japanese news sources reported TEPCO revealed meltdowns occurred in the fuel cells of units #2 & 3. NHK News reports Unit #3’s steam powered cooling system pump (RCIC) was lost at 2am on March 13, and fuel began to be uncovered several hours later. TEPCO believes fuel started melting in localized spots inside the core at about 9am. JAIF reports that by 3am on March 14, some 60 hours after the March 11 quake, most of the core had melted causing molten fuel to drop out of the cell and find its way into the bottom RPV head. The molten corium cracked and fractured as it dropped through the residual water in the bottom of the reactor vessel. It is not known if all residual water was eventually boiled off. TEPCO says it’s possible the core was never completely uncovered, and a full meltdown like that assumed for core #1 may not have happened. World Nuclear Assn. surmises that some water was being sporadically injected into the RPV during this most critical period, which may have averted full meltdown. But, it is safe to assume a slow process of additional fuel melting continued for the better part of three days until fire truck pumps boosted sea water “injections” to the RPV on or before March 17, stopping further melting.JAIF and NHK report unit #2’s RPV cooling function was lost at 1 am on March 14. It is possible all fuel cell bundles were exposed by 8am, March 15. Fire trucks were on the scene, but attempts to use their pumps to boost the flow of cooling sea water to the RPV were unsuccessful, probably because of the great a pressure. By 8pm on March 15, enough of the fuel core had melted to begin dropping into the bottom head of RPV #2. This was about 101 hours after the earthquake. A relatively slow progression of continual melting probably continued until fire truck pumps could begin boosting water flows on March 17.Both unit’s core decay heat levels had dropped considerably before fuel uncoverage began. Although the initial decay heat of both units might have been ~50% greater than unit #1 at shutdown, their longer time periods between tsunami and core uncovery made heat production in units #2 & 3 much less than was the case when unit #1 fuel cell was uncovered. Because of the lower heat production, the time periods between loss of cooling functions and the onset of melting for units #2 & 3 were considerably longer than with unit #1. From the reports, it now seems more probable that unit #3’s core experienced considerably more melting than unit #2’s core because fuel liquification began about 40 hours sooner. Even though the decay heat rate dropped slowly in unit #2, the 40 hour difference in the onset of fuel melt could have caused unit #3 to have as much as twice the level of meltdown as in unit #2.
TEPCO says it has taken more than two months to draw these preliminary conclusions because they were more concerned about controlling the accident situation than compiling and analyzing data. It’s a weak excuse. Masanori Naito of Japan’s Institute of Applied Energy told NHK News says confident analysis of the data available since mid-March should have taken no more than a day. He added it would have been relatively “easy” for TEPCO to have come to this conclusion much, much sooner.
- This morning, all Japanese news media, reputable international nuclear information sites (e.g. WNA) and JAIF report holes were burned through the RPVs of units #1 & 2. The number of holes and cracks from the burn-through episodes total the equivalent of a 10 cm (4 inch) hole. This speculation comes from a computer simulation run by TEPCO. The primary, if not sole origin of these computer-based speculations comes from pressure instrument readings inside each RPV from March 11 through March 15.These speculations are rife with problems. First, the corium would have to have been molten long enough to burn through 8 inches of solid, cast, high-carbon steel. For this to happen, the corium in the bottom head would have to have been dry for many hours. However, even at the very low level of sporadic injection flows into the RPVs between march 11-15, it is highly unlikely that the corium was completely molten long enough for such a severe burn-through.Second, if a burn-through of this magnitude did happen, the cores would have rapidly depressurized…rapidly. And any level of re-pressurization would have been highly unlikely. That’s a very big hole. However, pressure indications show that while pressures dropped dramatically from time to time, there was never a complete depressurization of either of the vessels. TEPCO assumes the pressure drops indicated several moments of core burn-through for each of the RPVs. However, each of the suspect pressure drops come just after water injections began. Any physics teacher knows that introducing room-temperature water into a closed, super-hot container will cause a rapid, significant internal pressure drop due to quenching.
Third, TEPCO’s RPV-failure speculation entirely depends on the pressure instruments for the two reactors providing reliable read-outs during the peak period of high RPV temperatures. We now know unit #1 water level instruments suffered greatly due to the extreme heat, thus it’s safe to assume the same for units #2 & 3 water level instruments. Pressure instrumentation is just as susceptible to extreme heat-related malfunction as water level instruments. So why assume the pressure instruments worked OK, when the water level instruments failed? This website has maintained for weeks that there has been a constant mismatch between indicated temperatures and internal pressures for all 3 RPVs, making the accuracy and efficacy of the pressure instruments questionable, at best. Basing a computer simulation on highly uncertain data makes no sense!
The question may be asked…would not the temperature instruments also be too damaged to be relied upon? Possible…yes. But, temperature instruments have a much higher reliability factor in extreme heat conditions than pressure and water level devices, which TMI data and extreme accident laboratory experiments show us to be the case. The most reliable parametric indications during the March 11-15 period at Fukushima Daiichi, units #1, 2 & 3, are most likely the temperature devices. Pressure and water level read-out data is simply too unreliable to counted on…especially when it leaves the door open for the news media to give it a negative speculative spin.
On the other hand, JAIF and NHK’s report of cracked piping on unit #3 RPV makes sense. (more on this Friday?)
- It had to happen…much of the Japanese news media is beginning to use western news media “spin tactics” to try and keep their readers/viewers on edge. It doesn’t matter if a suggested possibility is highly unlikely. If it’s not absolutely impossible, it’s implicitly reported as a distinct possibility.For example…Kyodo News reports that some of the piping attached to the #3 RPV might have been damaged by the earthquake itself, implying TEPCO’s statement of no earthquake damage is false. JAIF reports TEPCO as saying earthquake damage to any part of an RPV is highly unlikely. Thus, Kyodo News spins “highly unlikely” into “distinct possibility”.In perhaps the most disappointing example, Asahi Shimbun headlines “More radioactive water may leak from Fukushima plant”. The article attached says the storage tanks for the removal of the waters from the basements of the Fukushima power plant buildings are getting full. Does this mean more leaks to the sea is a distinct possibility? JAIF says 90% of the water in the unit #3 basement has been relocated, plus14,000 tons remain to be removed from each of the other basements. Unit #3 storage tanks are full, but not the storage locations for the other three. Further, once a water clean-up and filtration system is completed, the stored waters will be run through and used as reactor cooling replenishment supplies. Every gallon cleaned will be another gallon of additional storage space. At least Asahi adds it will be three or four days before the storage tanks for units #2 & 3will be filled. Regardless, the end is in sight. Does nearing the end of water removal mean more leaks? Highly unlikely, but…
- The Social Democratic Party of Japan (DPJ) has published a proposal to scrap all Japanese nuclear power plants by 2020. DPJ says the power loss can be recovered by 2050 using solar and wind generation. In the interim, government-enforced conservation plus increased production from hydro-electric, geothermal and “thermal” plants can keep Japan’s energy infrastructure from collapsing. By “thermal” they mean burning fossil fuels; mostly oil.There seems to be several problems with the plan, beyond the increased use of fossil fuels. First, DPJ’s estimate of hydro and geothermal generation is based on them operating nearly 100% of the time, which is horribly naïve. Hydro availabilities run in the 80% range, since the units have to be shut down periodically for maintenance and repair. Second, their outputs are seldom 100% of their design ratings due to several variables. A typical hydro plant averages about 50% capacity over the course of the year because the amount of water above the dam is less during dry seasons and much lower with winter’s icing and snowfall not melting. Geothermal capacity factors when operating are higher than hydro, at 90%. However, the corrosive nature of the steam generated in the deep, hot rock formations (lots of SO2 and CO2) cause material failures, making availabilities of about 65%.Finally, it seems DPJ falls prey to the traditional, overly-optimistic notion of solar and wind being a sure-fire, magical remedy. Using the latest, best estimates of future solar efficiencies, a solar farm of 1000 megawatts electrical (Mwe) would cover more than 10 square miles. (vice a 1000 MW nuke at a few hundred acres). A 1000 Mwe wind farm would be of similar size. To replace Japans nuclear capacity with solar and/or wind would doom more than 500 square miles of Japan’s precious, non-mountainous terrain. And, this doesn’t include that ideal solar and wind capacity factors necessarily run below 40%, meaning an additional 750 square miles of Japan’s land would be sacrificed to produce enough energy for non-productive period storage. The exacerbating solar problem is sunshine for only half of each day (on the average), and the wind farm problem of needing a steady 8mph velocity for the turbines to work (cut-in speed).
This website advocates a realistic mix of voluntary conservation, solar, wind and nuclear to wean the word off its fossil fuel addictions. Without nuclear in the mix, DPJ’s proposal is clearly unrealistic.
