July 27, 2013
On July 23, Tepco revealed that contamination is leaching into their inner port (quay) at Fukushima Daiichi. Tepco and the Nuclear Regulatory Authority make it seem as if the contamination is going into the Pacific Ocean. There are many unanswered questions with the groundwater issue, but one thing seems certain…the material is not reaching the open sea, at least not yet. Tepco’s recent revelation validates the NRA conjecture of 10 days ago. Tepco’s bases their belief on the water level in the near-shore sampling wells fluctuating with the tide. However, the data Tepco has posted over the past four months raises a considerable number of questions.
First we might ask…what is the source of the contamination? Since the groundwater contains Cesium isotopes 134 and 137, it cannot be coming from any of the waste water storage tanks or underground reservoirs at F. Daiichi. This is because those waters have been effectively stripped of their Cesium content by the station’s “makeshift” filtration system. There are several possible sources. (1) The radioactivity may be coming from basements of the four units holding 70,000 tons of water literally loaded with Cesium. (2) It could be what Tepco has said for more than a month and be residual isotopes already in the plant’s soil from a rather significant leak into a trench between unit #1 and unit #2 reactor buildings in April, 2011. (3) Could it have something to do with another trench from unit #3? Tepco quietly posted a Press handout concerning the possibility of a unit #3 leak on July 11. (http://www.tepco.co.jp/en/nu/fukushima-np/handouts/2013/images/handouts_130711_04-e.pdf ) Or, could it be a combination of all three?
If we assume the contamination is coming from the basements, it poses a pair of over-lapping questions. To begin, Tepco knows that 400 tons of groundwater is seeping into the basements every day. How’s the groundwater getting in there? Cracks in the concrete walls? Broken piping penetrations? The flowpath into the basements has not been stated. Whatever the path of seepage, groundwater is leaking into the basements and there’s no reason to think the contaminated waters are not leaking out via the same pathways. The Nuclear Regulatory Authority wants to freeze the ground surrounding the turbine buildings using an earth-freezing technology that does not yet exist. While the mere suggestion puts the technical competence to the NRA in question, if it works it will merely lower the in-flow of groundwater by 100 tons per day. Tepco already has what seems to be a better methodology to stanch the groundwater influx. They are drilling holes deep in the ground along the shoreline and inserting a chemical to harden the soil itself. (http://18.104.22.168/en/nu/fukushima-np/handouts/2013/images/handouts_130708_03-e.pdf ) Why not do the same thing around the basements of the turbine buildings, too? If it is good enough to keep contaminated groundwater from getting into the station’s near-shore quay, it will surely be better than the NRA’s pie-in-the-sky concoction to freeze the soil. Water-proofing the soils surrounding the basements, and around the suspect cable trench coming out of unit #2 should eliminate it as a source of possible leaks. Then there’s the unit #3 trench, but we’ll come back to it later.
Next, how bad is the groundwater contamination? Is it really “highly radioactive”? The highest groundwater Cesium reading to date is 11,000 Becquerels per liter inside one of the now-numerous sampling wells at F. Daiichi. Sounds like a lot, doesn’t it. Want to know what’s actually highly radioactive? The water in one of the trenches connected to the unit #2 turbine basement! The Press reports Tepco has found it to contain 2.35 billion Bq/liter of Cesium. That can be called “highly radioactive” by any standard. If 11,000 Bq/liter is “highly radioactive”, then what descriptive term should the Press use for 2.35 billion Bq/liter?
To continue, three of the groundwater sampling wells have elevated levels of Tritium (more on this later), but only one has shown increases in both Cesium isotopes over the past 2 weeks. (see the Tepco handout, above, for well locations). Well no. 1-2has readings of 11,000 Becquerel per liter for Cs-137 and 5,400 Bq/liter for Cs-134. (http://www.tepco.co.jp/en/nu/fukushima-np/f1/smp/2013/images/2tb-east_13072301-e.pdf ) These are the contamination levels that are always cited in the Press, both inside and outside of Japan, even though the Cesium in the rest of the wells is about 100 times lower. But here’s the important point…when the sample water from well #1-2 has the suspended solids filtered out, the cleansed water has readings of 50 Bq/liter of Cs-134 and 71 Bq/liter of Cs-137. (http://www.tepco.co.jp/en/nu/fukushima-np/f1/smp/2013/images/2tb-east_13072303-e.pdf ) These readings are higher than the other four near-shore sampling wells, but more than 99% lower than unfiltered. This demonstrates that the vast majority of the Cesium in the unfiltered sample is contained in the suspended sediment, probably stirred up by the fluctuating water level in the well. So, why doesn’t Tepco post the filtered sample data along with the unfiltered for well #1-2? It seems they only posted the unfiltered data only once on July 22nd. Further, has Tepco attempted to filter the sample waters taken from the other near-shore wells? If not, why not? This could be significant.
Here’s why it is important. Since the filtering of suspended solids removes more than 99% of the radioactivity, the Cesium is clearly bonded with the soil. The only way the high levels of Cesium in the groundwater can get into the station’s quay would be if the soil itself is being spilled into the seawater. Is it? With the station’s quay effectively isolated from the outer port area, and the outer port surrounded by some massive break-walls, there is no shore erosion. There might be a tiny loss of Cesium-impregnated soil leaving the shore, but the vast majority is staying put. We can say this with confidence when we look at the Cesium level inside the essentially stagnant quay. We find that all sampling points have not demonstrably changed in Cs-134 and Cs-137 concentrations since early April. (http://www.tepco.co.jp/en/nu/fukushima-np/f1/smp/2013/images/intake_canal_130726-e.pdf ) The levels have fluctuated over the past four months, but that is to be expected with activity levels as low as these in full liter samples. The range of upper and lower fluctuation points has stayed quite constant for all 12 sampling points along the quay’s shoreline. If there is a “highly radioactive” leak coming out of unit #3, there does not seem to be an increased Cesium level to prove it. It should be noted that the Cesium levels inside the quay have not changed significantly since March, 2012, but the above link back to April 2013 should suffice for this commentary.
Next we have the detected Tritium (H3), which raises more questions. Well number 1-2 has an H3 level of 350,000 Bq/liter, well number 1-3 is at 270,000 Bq/liter, and well #1 has 420,000 Bq/liter. (Wells 1-2 and 1-3 are between units 2&3 reactor buildings, and well #1 is next to reactor building #1) The Cs-134 levels in both well #1 and well 1-3 are…undetectable! The Cs-137 in both is less than 1Bq/liter. Why is the well with the highest level of Tritium not showing any Cesium? There is no correlation between H3 concentrations and the Cesium concentrations. There ought to be a correlation, but there isn’t. Why is there no correlation between isotopic concentrations? On a related note, why is there an elevated level of H3 (1,100 Bq/liter) at the unit #1 near-shore sampling point, but less than 400 Bq/liter everywhere else in the quay? If there is a leak to the quay is out of the unit #3 trench, why isn’t the quay water adjacent to unit #3 showing an increase over the levels detected in April?
Finally we get to the ultimate question. Is any of this contamination going out to sea? The inner Quay is sealed off from the waters which are inside the heavy stone break-walls that surround the station. The break-wall has a single opening to the open sea. Seawater sampling outside the quay, but inside the break-wall shows nothing. No detectible Tritium…no detectible Cesium. It appears the contamination in the quay is not getting into the outer port area. The silt dam that seals the entrance to the quay seems to be doing its job quite well. In addition, samples taken from the open sea surrounding F. Daiichi also show nothing. In other words, there seems to be no groundwater-borne contamination going into the Pacific Ocean from Fukushima Daiichi. So, why do the Nuclear Regulatory Authority and Tepco both make it sound like the Pacific Ocean is being “tainted”?
Many might question the veracity of the data posted by Tepco’s staff at F. Daiichi, given the general level of distrust relative to the company. But, there is no-one else’s data to analyze. Keep in mind that Tepco discovered the problem with groundwater contamination. No-one else did. They are the ones who have reported it to the world, albeit belatedly…and there-in lies the problem. The company’s level of transparency relative to public disclosure is not perfect, and some of their statements may be tainted with paranoiac twists, but their radiological data should not be distrusted. We have no other data to go on.