UPDATE, May 12, 2017: Namie City government reports that as of 3:05 pm on May 10th, the Mount Juman fire was no longer burning. A city official we contacted by phone said that about 50 hectares had been burned in all. Radiation monitoring posts detected no increase in radiation levels in residential areas, but the Mainichi Shimbun reports that monitoring done in three nearby villages on May 8th shows a 3 to 9 times increase in radioactive Cs137 concentrations in airborne dust. The three locations are:
— Namie-cho, Ide no Yasuragi (about 2km from Mount Juman) airborne Cs137 3.23 mBq per cubic meter, up 3.23 times
— Futaba Town, Ishikuma, Ishima community hall (about 4km) 7.63mBq per cubic meter, up 8.98 times
— Okuma Kumaichiku Community center (about 8km) 1.35mBq per cubic meter, up 3.86 times
(From May 2nd, 2017) A forest fire has been burning in the no-entry zone of Namie in Fukushima since April 29th, and is now in its fourth day. This has been the subject of many news reports of varying quality, and we are following the situation closely.
The site is among the most highly-contaminated by the Fukushima disaster, well within the “difficult-to-return” zone. Clicking this link will center the Safecast web map on the site of the fire at Juman-yama, which we derived by comparing terrain in news videos and in Google Earth.
To summarize what has been reported so far:
— The fire is in a mountainous area of Namie Town called Juman-yama, about 10 km from the Fukushima Daiichi plant. The Daiichi plant itself is not at risk from this blaze.
— The fire appears to have begun on Sat. April 29, caused by a lightning strike.
— Fire-fighters used helicopters to dump water on it, and it appeared to have largely died out on the morning of April 30, but high winds revived it shortly after.
— The burned and burning area has been growing, and as of May 2 was approximately 20 hectares.
— We don’t have much information about wind direction, which is variable, but predominant winds would blow the smoke eastward towards the ocean (generally over the Daiichi plant site and the towns of Okuma and Futaba).
— The most informative news report we’ve seen so far is from Fukushima Chuo TV, on May 1. Prof. Kenji Namba from Univ. of Tokyo notes that the fire can be expected to spread radioactive cesium from the trees in smoke and ash, a general risk pointed out by many experts in the past. He also notes that a monitoring post at Tomioka Station, about 15 km to the southeast of the fire site, has shown what appears to be a very small increase in radiation levels there since the start of the fire. We believe that data from many more points should be examined before ascribing any significance to this kind of reading.
Our closest Pointcast fixed sensor in the area is in Namie, about 7.8 km to the east-northeast of the fire. Its readings have remained relatively constant since the start of the fire, with no appreciable change in radiation levels detected. The time series graph for this sensor showing the change in radiation over the past 30 days can be accessed here.
We also have Pointcast sensors in the nearby towns of Tomioka and Odaka. Neither these nor any other Pointcast sensors show any appreciable increase in radiation levels so far.
Examining readings from government radiation monitoring posts shows what appear to be noticeable “bumps” at some locations around May 1. But these are not large spikes, and in general appear to be within the range of the variation seen in recent months. However, any detection at all would depend on the direction the wind is blowing the smoke plume.
Though any increases in radiation dose rates seen so far appear to be very small, inhaling the smoke from this fire could lead to an internal dose of radioactive cesium. We strongly suggest that people avoid inhaling this smoke. The area surrounding the fire where such risks would be highest are in fact closed to the public and therefore inaccessible, but the additional radiation risk to firefighters is making it difficult to send adequate personnel to battle the blaze.
News videos here: