As this web page has reported for many days, there is unquestionably fuel damage in Fukushima Units 1, 2 & 3. How much is purely speculative, at this point. Because of sporadic over-pressure conditions inside each of the three reactor vessels due to decay heat production, relief valves automatically opened and dumped radioactive steam into the pressure-suppressing torus of each. The torus contains a large volume of water. The steam from the reactor is released below the torus water level, and a considerable amount of combined boiling and steam condensation takes place. It is a very chaotic situation inside the torus when pressure is relieved from the reactor. Obviously, the water in the torus gets heated rapidly, and the interior becomes a helter-skelter mixture of steam and water. Naturally, pressure inside the torus increases. At Fukushima, if and when internal torus pressure reaches a pre-determined limit, another relief valve system actuates on the torus itself, letting a mixture of steam and water be exhausted outside the plant. The secondary containment surrounds the primary containment and houses at least four floors of auxiliary equipment, each of which is built entirely out of thick, steel reinforced, high-density concrete. Part of this secondary containment extends outside the Reactor Building, under the turbine generators in the attached Turbine Building.
The contamination levels and isotopic content of the waters found in “puddles” on the Unit #3 turbine basement floor, and in the building drains, were reported here yesterday. It was also reported that the analyses indicated the much of the water came from the spent fuel pools. Further, it was reported that this strongly indicated that there was no breach of reactor or primary containment integrity. Reactor water level and pressure monitoring systems have been electronically recovered. Water levels are constant and pressures are constant as well, in each reactor. This indicates the reactor vessels are intact. Also, pressure monitors inside the primary containments have been re-energized, and pressures there are constant. This suggests that the integrity of none of the three reactor vessels or primary containments have been compromised.
To expand on yesterday’ report, the water-borne contamination in the turbine building basements and drains did not only come from the spent fuel pools during spraying. There is also, most certainly, some reactor fuel-damaged isotopes in the mix, due to torus pressure relief transients. A quick glance at the contamination concentrations for each isotope, published by the Nuclear and Industrial Safety Agency (NISA), shows the radiological concentrations of Chlorine-38 (a neutron activation product) and Cesium-137 (fission by-product) are about equal. This could only be the case if the waters came from both sources.
This does not mean that half of the water came from the reactor and half from the spent fuel pool. But, a look at the respective half-lives of the two isotopes gives us a powerful clue. Cl-38 has a half life of 37 minutes. Cs-137 has a half life of 30 years. The differences reveal many levels of information, but the one germane to our topic is this…radioactivity diminishes only as fast or slow as the isotopes’ half life. The shorter the half life, the quicker it burns itself out. Total loss of radioactivity is no more than ten half-lives. Thus, the Cl-38 radioactive lifetime, before it is gone, is a little over 6 hours. The probable time delay between the Cl-38 being formed in the spent fuel pools, flushed out by the water sprays, and finding its way into the basement…including the additional time it took before the “puddles” and drains were discovered to contain the Cl-38…must have been a few hours, at least. Let’s say 3 hours. That’s roughly 5 half lives, which would have reduced the radiological concentration by a factor of 32 (two to the fifth power). For the analyzed level of Cl-38 to be equal to Cs-37, the initial radioactivity level must have been 32 times greater than the Cesium. Thus, it is safe to say most of the contaminated water came from the spent fuel pool of Unit #3.
Now for more radiological news…
- Early today, TEPCO released a report that an enormous increase in the radioactivity level of the “puddles” had occurred. They reported an increase by a factor of 10,000,000. Less than an hour later, they retracted the report with considerable apologies. There has been a reported increase, but by a factor of 25. These numbers are about ten million times greater than what would be typical for the water flowing through the reactor during routine operation…which are actually very tiny concentrations to begin with. Reactor water is so pure that it barely conducts electricity! Regardless, the 10,000,000 number relates to ultra pure reactor water concentrations, but not to any kind of increase since yesterday. Further, it seems the new readings were from puddles different from the one analyzed yesterday, and these puddles are located in the Unit #2 turbine basement. This is yet another example of TEPCO’s poor communications, not only between TEPCO and the Press, but internally between TEPCO informational staff and the staff toiling at the Fukushima plant itself. In addition, we are now seeing indications of informational panic. Before publicly reporting radiological readings that seem astronomically changed in a very short period of time, TEPCO spokepersons should be skeptical. Very skeptical. They should have re-checked and triple checked the information. Verification to the Nth degree. If true and verifiable, then and only then report it. Reporting massive radiological changes without major changes in the plant’s equipment or containment status can be, and now has been, an informational disaster. All prudent efforts must be made to improve news media and public confidence in TEPCO press statements, but this has surely brought confidence in TEPCO information to a new low. Up until now, TEPCO’s press statements have been relatively thin with respect to content, but they’re information has ultimately proved correct. Now, the level of confidence that may have been previously established has been diminished, if not lost completely. In addition, the new, higher readings came from the turbine basement adjacent to Unit #2, not yesterday’s Unit #3 discovery. Unit #2’s spent fuel pool received considerably more seawater spraying than the other three because it still has a roof and walls surrounding it. The spraying was through the few holes which seem to have been caused by flying debris, which would has greatly inhibited getting the sprays directly to the #2 pool itself. As a result, the dilution of boric acid levels in that pool must have been greater than with the other three pools. Thus, low level fissioning in the pool must have been greater than the other three, producing a higher concentration of neutron activation isotopes and higher “puddle” radiological readings. Which leads to the next item of interest…
- It has become increasingly apparent that the Fukushima Health Physics (HP) staff is either overwhelmed or incompetent. Or both. TEPCO now reports that there are several highly contaminated “puddles” in all four turbine building basements. These “puddles” did not magically appear. They must have been there, building up in their size and depth, for days. Before any worker should be allowed into a contaminated or potentially contaminated area, regardless of their radiological protection training level, detailed scans with sensitive portable monitors by HP professionals must be performed. “Hot spots”, precise locations of high radioactivity and their dimensions, must be identified and depicted clearly on maps of each area to be entered. Each person who enters the area must be fully indoctrinated on these hot spots, given a copy of the “hot spot” map or maps concerning where the worker will be going, and apprised of all prudent precautions to be taken to avoid these “hot spots” along the way. Further, when radiation levels are found to be high in areas where necessary work must be performed, an HP professional with sensitive monitoring equipment must accompany the workers to insure that their safety will not be compromised. From Japanese Press reports, TEPCO admits that few or none of these precautions were taken, in order to expedite stringing of emergency power cables. Good HP practices must never be compromised, especially when the risk of further core fuel damage to any of the reactors has already been virtually eliminated, as was the case before yesterday.
- Two bad results have come from the above two items. First, the stringing of emergency cabling in the turbine building basements has ceased until a detailed monitoring of the turbine building basements is complete and all “hot spots” have been clearly identified. This will agonizingly lengthen the time it will take to bring the reactors in Units 1, 2 & 3 into the ultimate condition of safety; cold shutdown. Second, all Japanese Press services are lambasting TEPCO for bad communications and a severe lack of concern for the safety of Fukushima employees…and they have ever reason to do this!
- On a more positive note, the Japanese Press reports the three workers sent to the hospital yesterday are in good condition, but remain under observation. Tests done on the ankle burns to the two contaminated workers have revealed how much beta skin dose they probably got…between 200 and 300 sieverts! That’s not life threatening, nor is it “limb threatening”, but it is a whopping big dose. Biggest beta skin dose this writer has ever heard of. That level of skin dosage would result in burns similar to very severe sunburn.
And, finally, today’s technical update on the emergency status of Units 1, 2 &3…
…not much from TEPCO! However, The International Atomic Energy Agency (IAEA) reports…
- the control rooms of all three units now have electric power and the lighting systems re-energized (as well as many reactor and containment monitoring read-outs). Reactor internal environment and primary containment monitors are providing good data.
- Freshwater is now being used to replenish all reactor water levels.
- Reactor internal temperatures in #1 and #2 are coming down. Reactor #1 is at 142 degrees C, and dropping. Temperature in reactor #2 has dropped to 97 degrees C, which is below the boiling point of water.
- Pressures inside all three reactors have “stabilized”.
- Plans are being made to transfer the contaminated waters in the turbine building basements to the voluminous condenser tanks attached to the bottoms of the turbines. This will reduce the chance for continued drainage to the sea, if not eliminate it entirely. This will also reduce radiation levels in the turbine basements and severely reduce the risk of future worker contamination experiences, allowing the emergency cable-stringing efforts to resume.