Kyodo News - radiation dose rate at Fukushima No. 1 spikes to 8,217 micro sievert (per hour)

[jpak]

http://search.japantimes.co.jp/cgi-bin/nn20110315x3.html

<snip>

The agency said the explosion at the No. 2 reactor may have damaged the "suppression chamber," a facility connected to the reactor's container which is designed to cool down radiation steam and lower the pressure in the reactor. It said a sharp decline in the pressure level of the chamber suggests damage.

Following the incident, the radiation level near the main gate of the Fukushima No. 1 plant exceeded the legal limit to reach 965.5 micro sievert per hour at 7:00 a.m. and jumped to 8,217 micro sievert at 8:31 a.m., the agency said. The latter amount is more than eight times the 1,000 micro sievert level to which people can safely be exposed in one year.

Given that the building housing the reactor has already been damaged by Monday's hydrogen blast at the neighboring No. 3 reactor, a spread of radiation outside the plant has become a serious threat, experts say.

The possibility of a meltdown, in which fuel rods melt and are destroyed, "cannot be ruled out" as the fuel rods have been damaged, the utility said.

<more>

[dixiegrrrrl]

1. What are micro sieverts????

And what is the "normal" range/how is it measured?

[NMDemDist2]

2. i looked at wiki for the same question

1 Sv = 100 rem
1 mSv = 100 mrem = 0.1 rem
1 μSv = 0.1 mrem
1 rem = 0.01 Sv = 10 mSv
1 mrem = 0.00001 Sv = 0.01 mSv = 10 μSv

http://en.wikipedia.org/wiki/Sievert

The millisievert is commonly used to measure the effective dose in diagnostic medical procedures (e.g., X-rays, nuclear medicine, positron emission tomography, and computed tomography). The natural background effective dose rate varies considerably from place to place, but typically is around 2.4 mSv/year <2> (pdf).
For acute (that is, received in a relatively short time, up to about one hour) full body equivalent dose, 1 Sv causes nausea, 2-5 Sv causes epilation or hair loss, hemorrhage and will cause death in many cases. More than 3 Sv will lead to LD 50/30 or death in 50% of cases within 30 days, and over 6 Sv survival is unlikely. (For more details, see radiation poisoning.)

[SpoonFed]

3. NHK is reporting at this very moment

That there are readings of 100mSv and 400mSv around this plant if not more.
Specifically at 10:22am local time around No.3 400mSv and No.4. 100mSv

The units are millisieverts, not microsieverts.

There is a 20km radius evacuation order
and a 30km stay indoors order.

[jpak]

4. Yikes! 3 hours of exposure and symptoms of radiation poisoning will be presented

:wow:

[SpoonFed]

5. and...

there is more... distant monitoring stations are picking up higher than normal radiation levels. I missed the specifics in order to transcribe.

But there were reports very similar to this:
http://af.reuters.com/article/energyOilNews/idAFTKB00735920110315

I'm watching the live stream of NHK available at:
http://www.ustream.tv/channel-popup/nhk-world-tv

I think that one of the reports said they measured 3mSv
at a distance of more than 200km from the Daiichi plant.

[FBaggins]

6. Yep

Three hours of unprotected exposure (and they're not unprotected), but it's clearly more serious.

[CJvR]

7. Time frame?

100 mSv over how long a period? If it is on a yearly basis it is not particulary alarming, it is still ~40 times normal bg radiation. If those are hourly values things are much much worse, then they represent 360.000 times the normal bg radiation.

Whenever radiation levels are mentioned the time of the exposure is critical, otherwise it is like saying something is 50 degrees warmer... Warmer than what?

[itsrobert]

8. Any reason they can't throw a giant tarp over it

Or some type of giant filter to trap radiation? I was thinking some shielding is better than none at all? Just an idea, have no idea really.

[CJvR]

9. Water->steam

They need water to keep it cool, but the water boils away greatly expanding in the process. Normally they would run the steam through a condensor - but you need pumps and electricity to work that and if they had that then they wouldn't be in theis mess to begin with.

[itsrobert]

10. The US Navy has ships that are giant generators to supply electrity

I am guessing it's not safe to anchor a generator boat nearby the plant?

[CJvR]

11. Not even sure...

... it is possible to get a carrier of submarine in close enough to the shore, they are hardly shallow water vessels. Or even if the power generated would be compatible to the ground installations or in any way transformable into something useful. Then there is the continued seismic activity in the area, dump a sub on the beach and soon there will be yet another meltdown!