The two hot spot Prefectures have been advised to evacuate.
Get yours HERE
If you keep track of Ibaraki Prefecture and click that area on the map, you will get a table with first-rate information on airborne outflow of hazardous materials. Tochigi, Gumma, Niigata, Yamagata, Akita, and Iwate Prefectures complete the front line outside of Fukushima and Miyagi Prefectures.
Follow below-the-fold for explanation and comparison with Chernobyl. :::
Corporate media in America are pumping up the hazards of this situation. One could be excused, at least here in New York, for believing that Tokyo is in a collective panic. That people are fleeing for their lives.
Yes, there are hazards. Yes, there are risks of seeing greater hazards. But no, unless you are in the immediate area this is not a life threatening situation as of today.
Calculations based on current Detail Table data show Maximum annual extra exposure at below 1 REM-per-year.
Here are the maximum readings from the area immediately south from the two main areas:
Horiguchi Hitachinaka City
-- 856 nGy/h - 1:00 AM local time (on the 18th)
-- 872 nGy/h - 9:40 PM local time
-- 876 nGy/h - 7:20 PM local time
-- 881 nGy/h - 4:40 PM local time
-- 993 nGy/h - 3:00 AM local time
-- 1011 nGy/h - 11:50 PM on the 16th (previous night)
They are reporting nanoGrays-per-hour as equivalent to nanosieverts-per-hour using the default 1:1 conversion RBE factor. One explosion on the 16th had produced a one-time jump to 2114 nGy/h. Otherwise, the pattern shows a steady decline as water cools the Fukushima radioactive materials.
Horiguchi Hitachinaka City is seeing less than 1/1,000,000th of what happened downwind from Chernobyl.
Here's some math to help translate these data to threat assessment information:
1 Gray = 1 Gy = 1 Sievert = 1 Sv by convention
1 Sievert (SV) = 100 Rem, which means that
1 Gray = 100 Rem
The originally NBS-produced, now NRC-produced and published STANDARDS FOR PROTECTION AGAINST RADIATION states a clear limit: total radiation should not exceed 5 Rem per year.
The highest reported airborne radiation rate in Japan during this crisis got up close to 4,000 nanoGrays-per-hour.
1 Rem = 0.01 Grays
1 Rem = 0.01 * 1,000,000,000 nanoGreys
1 Rem = 10,000,000 nanoGrays
So let's do a bottom-line calculation for what the 4,000 nGy/h max exposure calculates to for a full annual exposure:
4,000 nGy/hour = 0.4 milliRem/hour
4,000 nGy/hour = 0.0004 Rem/hour
Annual total exposure =
0.0004 Rem/hour
- times -
24 hours/day
- times -
365 days/year
=EQ =
3.5 Rem/year
****
Horiguchi Hitachinaka City is seeing about a fourth of that with radiation level falling.
Added radiation at HHC is running under 1 Rem/year.
That sounds good: the total radiation exposure there runs 1 Rem/year for an Average Person outside, unmasked, unprotected. Imagine someone sitting on the pole with the radiation detector.
This radiation level at HHC is declining, as well, apparently because the water dumps from helicopters put out the fires and water is being put into the storage pools that hold the spent fuel rods. Declining radiation levels are always good.
However, that is not all there is to it. The mythical Average Person doesn't exist. Some people will get more radiation exposure, some less. This is likely be a Bell Curve problem, but the fit of the Bell Curve having a skew to the left. Most people will get lower exposure, even outside for full effect.
The right side values -- high exposure, not so many people -- will have a very few people with 10 times the average exposure, a very rare few above that.
Anyway... these are the observed facts, folks.
Keep track of the online Radiation Maximum map and use the calculation system presented above if things change significantly. You will be able to tell for sure which way things are going and who is at risk.
If you live in Ibaraki Prefecture or points to the south, do wear a filter-mask. Tochigi, Gumma, Niigata, Yamagata, Akita, and Iwate Prefectures are certainly close enough so that preparations for a wind change are indicated.
The N99 and N100 painters masks are perfect enough. The simple cloth thingies that people wear to deter flu, not so much. And do take the potassium iodide pills !
Good luck, everyone !
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To repeat: the online Japan Radiation Maximum map is HERE.