- A 10 meter by 1 meter sidewalk near a school in Tokyo’s Setagaya Ward was discovered to have an exposure level of 2.7 microsieverts per hour, which is higher than the rest of the sidewalks in the ward. The ward made the walkway off-limits for children walking on it on their way to school. The patch of sidewalk was decontaminated by high-pressure spray last month, with virtually no decrease in rad level. The ward said they didn’t know what to do about it. If someone stood on the sidewalk constantly for 16 hours a day, every day for a year, the accumulated exposure would be 15.6 millisieverts, which is below the 20 millisievert national exposure standard. Actually, students walking to school would be on the sidewalk no more than a few minutes each day, and only on school days. Thus, their total dose would be 0.016 millisieverts, which is less than regularly eating bananas and broccoli. Further, if the power washing had little effect, the source was probably not Fukushima contamination. However, unbridled fear of radiation by some parents forced the ward to make the sidewalk off-limits. (NHK World)Today we find out the radiation scare was exaggerated, and the source had nothing to do with Fukushima. This new information has been reported in all Japanese newspapers and on all TV news stations. As it turns out, the 2.7 microsievert level was on one small portion of the walkway. 90% of the sidewalk was much lower. Further, the rad level was lower at the surface than at 1 meter height, which is the reverse of what contamination would cause. Survey logistics indicated the radiation field was coming from a house behind the fence next to the walkway. After the owner got home and gave the technicians permission to search the premises, a box was found under the house. The box contained several jars of a power suspected to be Radium. The Box’s contact reading was 600 microsieverts per hour (more than 5 sieverts per year). The box was placed in a lead-lined container and the exposure levels on the sidewalk dropped to about 0.2 microsieverts per hour, which is typical for the ward. Each news service in Japan put a different “spin” on it. Kyodo News Service is perhaps the worst saying, “Powder inside the bottles is radium, easing public anxiety that the contamination could have been related to the nuclear crisis at the crippled, radioactive cesium-leaking Fukushima Daiichi nuclear plant over 200 kilometers away.”
What? A 5 sievert per year exposure level is a whopping big one, no matter what the source is! Since when is a high exposure level from Radium of less concern that the many times lower exposures from Cesium? Radium is chemically similar to Cesium, so it has the same theoretical health effects. And, 5 sievert per year exposure (using the linear, no threshold hypothesis) is supposed to kill 50% of those people exposed. And this is supposed to ease public anxiety? Oh…we forgot…the Radium didn’t come from a nuclear power plant.
- Yesterday, Fukushima Daiichi held a nuclear emergency drill. It was largely to new fire truck pump connections to the feedwater pipes for low pressure injection of cooling water. This was in keeping with the revised regulations which followed the March 11 tsunami. The new regulations call for having additional connection devices on the plant feedwater piping. The drill was called a complete success. (NHK World)The problem is this. Fire trucks were at the Fukushima power complex less than 8 hours after the tsunami hit, and before fuel damage started in unit #1. Because of bureaucratic and procedural delays, the plant wasn’t depressurized soon enough to make effective use of the low pressure fire pumps. These additional connections will make no difference if the plant is not allowed to be depressurized.
- JAIF’s weekly posting of conditions at Fukushima shows units #1 and 3 RPVs are now down to 73 oC, and unit #2 down to 84 oC. In addition, the waste water decontamination systems have now cleansed a total of 125,000 tons of liquid. However, ground water leakage into the turbine building basements is keeping the volume yet to be cleansed at ~80,000 tons. However, the ground water is certainly diluting the basement waters, lowering the total concentrations of Cesium and Strontium. In addition, four locations for radiation level monitoring are now being posted, instead of only the main gate to the power complex. The main gate is now at 29 microsieverts, another “border” location (unspecified) is at 5 microsieverts, a reading of 298 microsieverts next to the main office building nearest unit #3, and 12 microsieverts at the shoreline.
- The Tokyo Metropolitan government has decided to use all Cesium-laced incinerator ash and sludge below 8,000 Bq/kg for a Tokyo bay landfill. It will be part of a beefed-up breakwater. Tokyo’s Ota and Koto wards, which are adjacent the area for the proposed breakwater, have reportedly agreed on the measure. The ash containing radioactive materials was produced by water treatment facilities in Tokyo’s Tama district. (Mainichi Shimbun)
- The Japanese Education Ministry has published booklets to provide students with basic knowledge on radiation, in response to increasing calls for such classroom materials since March 11. The ministry released the 20-page booklets on Friday. There are three versions; elementary, junior high, and high school. The books focus mainly on basic information on radiation, its effects on human health, and ways to protect oneself from radiation exposure. One interesting point in all three booklets is the statement that Japan’s average natural background level is 1.5 millisieverts per year. This is 50% more than the recently established exposure tipping point for decontamination which is 1 millisievert/yr. Did the Education Ministry contact the Ministries charged with setting the decontamination standard? It seems not. Further, since Japan is mostly mountainous terrain, which is always 3-5 times higher background than sea-coasts (where to data for the current Japanese “average” number comes from), it is probable that the national average is more like the Colorado Plateau in the US, which is 5-6 millisieverts per year.Other than college courses for radiologists and radiation biologists, there has been essentially zero education on radiation and it’s effects anywhere in Japan, until now. This is the first national education program of its type in Japan. Better late than never? It’s never too late to start all over again…