"Should I Stay or Should I Go?"

Last updated Mar 17, 2011 10:35 am local time (9:35 pm EST)

Current situation as of morning of March 17. Tokyo radiation level remains within normal range.

JSDF helicopters attempted four successive water-dumps over reactors #3 and #4. The condition of those reactors is most troubling, as the spent fuel rod cooling ponds have evaporated and without refilling them, there is a high chance the rods will overheat, melt, and release radioactive material. The results of the water drops have yet to be announced.

Current situation as of evening of March 16. Tokyo radiation level remains within normal range.

Fukushima Reactor #1: in spite of explosion, containment housing believed unbreached, sea-water injection ongoing to lower temp of fuel rods, situation stabilizing.

Fukushima Reactor #2: leaked some amount of material, causing radiation spike this morning around 10am. Cause unknown. Rad level has been dropping steadily since.

Fukushima Reactor #3: vented what appears to have been steam earlier today. Suspicions that containment housing may be breached. Conditions preclude direct observation. There is a very high chance the pool containing spent fuel rods has completely evaporated and rods are melting, irradiating the area. A planned water-drop by helicopter had to be called off due to radiation counts exceeding safety limits for the pilots.

Fukushima Reactor #4: fire broke out this morning, since extinguished. Theory is that evaporation of spent fuel rod storage pool caused hydrogen build-up that caught fire. Fire occurred in area where seawater pump was placed, and radiation has slowed but not stopped efforts to add water to pool.

---------------------------------

It pains me to say this, but in the wake of the situation at the Fukushima nuclear power facility, there has been a lot of innuendo about the potential danger to the Tokyo metropolitan area. The following represents all of the current information released to date about the situation in Japanese press conferences and from other sources mentioned below.

I'm not a nuclear authority. I welcome all info, even contradictory info, so we can piece together a picture of what is happening without needing to sensationalize things. If anyone has data that contradicts any of the below, or sheds light on it, PLEASE comment so that I can amend it. 

The bottom line is, the Tokyo metro area seems to be safe for now and there is no need to panic or evacuate. There is no "fallout cloud" approaching Tokyo, as some media would have you believe. I base this on the following data points. They are collected from information announced in government press conferences and from other sources cited below.

Point 1: A sievert (whether milli- or micro-) is a measure of exposure, expressed per unit of time (in the case of info coming from Japan, by the hour). The effect is cumulative. This means that at a 2 mSv/h (millisievert / hour) level, you would need to be exposed to the source for 100 hours to be irradiated to the point that is considered clinical radiation poisoning (200 millisieverts, according to this chart translated by @gakuranman). But the current background radiation in Tokyo is somewhere around 0.3 microsieverts. That's something like three ten thousandths of a millisievert.

Point 2: As reported by NHK and corroborated by datafeed from the Hino monitoring station, metropolitan Tokyo radiation levels rose from a normal reading of around 20-30 CPM (0.2 - 0.3 microsieverts per hour) up to to 89 CPM (0.89 microsieverts per hour) for an hour, then dropped to close to normal background levels again. They remain normal as of this writing.

Point 3: Tepco released a graph showing a spike of 12,000 microsieverts (12 millisieverts per hour) at front gate of the Fukushima nuclear power plant. It has since dropped to below 2,000 microsieverts (2 millisieverts per hour) This seems to correspond to the fire at reactor #4, which has since been extinguished. 

Even still, again note @gakuranman's chart showing comparative radiation levels. Even one hour at 12 millisieverts (the max reading taken at the gate of the plant) is equivalent to less than 2 CT Scans. These readings were taken at the front gate of the nuclear plant in Fukushima. They decline rapidly with distance from the reactors. Again, metro Tokyo readings remain normal.

Point 4: The situation at the #1 and #3 reactors is under control, with seawater being pumped in now to keep the cores cool. There was no core breach. The situation at #2 is that water is being pumped in but the level is not rising. This needs to be watched closely. The fire in Reactor #4 was extinguished earlier today. A measure of radiation and some radioactive isotopes may have been released in this fire, but the release of radiation and material seems to have stopped with the extinguishing of the fire. The big issue at #4 now is a potentially dropping water level. But as stated above, radiation levels are corroborated by the Hino geiger counter datafeed.

Point 5: The biggest issue as of the the afternoon of March 16 is that the situation at the reactors has not improved, though it is not clear if it is worse. A fire broke out at #4 early this morning (since extinguished), while elevated temperatures were detected at #2 and smoke or steam issuing from #3. Elevated radiation levels were detected at the front gate of the plant but have since dropped. There was a brief rise in background radiation levels detected in Tokyo early this morning (apparently corresponding to the fire at #4) but it has returned to normal as of this writing. As of right now, the danger appears confined to the plant grounds itself. The repair/firefighting crews remain on-site and working. (Many foreign media are incorrectly reporting the plant was "abandoned." This is not true.)

Again, PLEASE comment if you have info that contradicts any of the above.

This is a fluid situation, and an environmental disaster around the reactor site, but Tokyo residents and those outside of the evacuation zone do not seem to be in immediate danger as of this writing. The people in the most danger are the workers inside the plant. By exposing themselves to higher than normal radiation levels, they are sacrificing their health to keep the rest of us safe, and are the unsung heroes of this potential crisis.

Thanks very much to Andy Szymanski for summarizing this data and co-authoring this article.

Comments

[sophie]

Thank you for compiling this Matt, it is reassuring now that I have decided to stay in Tokyo. I hope you are right that we are at no great risk as it stands. Still sleeping with one eye open and the rest of the time all eyes on the news!

[Jeff]

Finally some numbers-based facts. I've been slightly panicked at the lack of information, but if what you say is true it seems (once again) to be a lot of media hysteria in search of a nice lead story. Thanks for this.

[Gunsim]

Great and informative post. I found the following post on the subject fascinating as well from some experts with the International Disaster Response Network (@IDRN_News) that you might find interesting for discussion: "Here is our REAL Risk Assessment of Japan's Nuclear Plants" http://ow.ly/4ewph

[Matt]

Thank you for this compilation, you are helping to inject some common sense into the overall panic.

The situation after quake & tsunami is horrible enough, so it is good to see that there are people who assess the nuclear situation with some common sense.

I have deep trust in the Japanese people and know that they will be able to eventually cope with this catastrophe.

[Cedric - Color Lounge]

Thanx Matt

[William Van Hecke]

Wow, thanks for this. And I wasn't expecting to see it, but thanks for the confirmation that Andy is okay. Hi Andy!

[Peter real]

Decision if you stay or go is very personal. As much as you want to rationilize it you will not find a simple answer. It depends on your responsibilities in tokyo. There is a certain risk that this situation will get out of control. In my opinion if there are no mandatory reasons to stay in japan right now it is better to temporarily leave.

[my]

thank

[Zdavatz]

Excellent Reporting! Thanks! This is very helpful!

[Karin]

Thank you. This is better than all information on tv together. Our thoughts are with you. Karin, Germany

[Margaret Jane Nakiyuka]

This information is good puts our minds at ease as long as it remains within the factual line. In situations like these for various reasons it is hard to find facts. Understably facts may cause panic and it is also very important to manage information at this delicate time in a way that does not upset the already upset. Looking at all the facts on the table it is probably safer and reasonable to get the truth however bitter. it does give one direction of what to do next
Uncertainty causes panic too.

[Shii]

It may be helpful to use the banana scale, since people can't relate to CT scans:

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

The current level is about 1 banana per day.

[Andy Szymanski]

Some more relevant data I have gathered:

-Fire broke out at 9:38 AM at the #4 reactor. This timeline matches perfectly with the spikes that we've seen at the gate of the facility (Tepgo graph) and the resultant spike from the Hino monitoring station (given a window of 2-3 hours for winds to bring it down to Tokyo)

-NHK has announced that Setagaya and Shinjuku monitoring posts read 0.89 (or 0.809; seems to be some typos) this morning, meaning that the Hino monitoring station is tracking correctly. I believe this means we have an accurate source.

[Kinny]

Thanks very much for compiling this info, Matt!

I’ve been following you closely on Twitter, as well as many others who (I believe) are in authority to make solid and unsensational comments. Yet, it’s still difficult to piece the overall puzzle together.

I hope that those, who are currently in Tokyo, or in the region of Fukushima, who are not able to digest the countless messages in the local tongue, can take some level of comfort in the information that Matt has provided since the beginning of this natural disaster, possibly the worst that I’ve seen in my lifetime.

[Melinda]

Awesome, Matt. I'm sending this to my parents.

[cassandra Harada]

I would like to send you a hug from Fuchu-Shi. Thank you for this, you made it much easier to understand!

[Mandy]

Matt, you got the sievert explanation wrong- you can get a chronic or acute dose. Acute means a high dose in a short period, while chronic means many little doses over a long period. Sievert is a measure of total (accumulated) dose. The dose rate is measures in Sieverts/time, e.g mSv/hr; Sv/day; etc.

[matt]

Hey Matt - this report says there was a 400,000 microseivert blast (http://www.jiji.com/jc/c?g=soc_30&k=2011031500861&j4). How does that factor into all this?

[CoCreatr]

Thank you for this summary. My own measurement of radiation in Yokohama roughly correlates with the data shown in Hino. Just keep in mind that this particular cloud must have been material released earlier, not from the fire this morning. At wind speeds today, it would take 10-15 hours to travel from Fukushima to Tokyo/Yokohama. Fortunately, the wind has turned and until Wednesday evening, further exposure is unlikely. Now if we could find more ways way to silence the self-important panic-mongers ...

[Chris O.]

Excellent article and counterpoint to all of the media hysteria and anti-nuclear Luddites who are using this incident to further their agenda. Thank you for posting!

[Andy Szymanski]

Additional relevant data (most courtesy of NHK):

-Radiation readings in Iwaki City, Fukushima (approx. 40 kilometers from the reactor) peaked at 23.72 microseiverts/h early this morning, but soon dropped to 3.94 microseiverts/h 2 hours later. Higher than usual for certain, but not substantial (it would take approx 1,725 hours exposure at this level to equal one CT scan).

-Radation levels in Tokai Village, approximately 110 kilometers from the reactor, reported levels of 5 microseiverts/h in the morning that soon dropped to 2 microseiverts/h by noon. Once again, higher than usual but still very low (almost 3500 hours of exposure to equal one CT scan).

The above, coupled with the readings that we know of in Tokyo proper (0.89 microseiverts/h at around 12:30) indicate with facts what the experts have assured us all along - radation exposure drops off at an exponential rate to distance from source.

Numbers don't lie, my friends.

[me]

matt of 400,000: that was inside the plant. As reported by Matt, the reading in Tokio had a peak of 1 microS because of that blast and the readings at the plant's main entrance are now back to around 2 miliS.
So, there was a peak of high release but that was controlled with the end of the fire in reactor 4.

[Simon Allen]

This is really great, thankyou.

[Paco]

Well, the geiger level chart I saw was not as optimistic as the one you have posted:

http://tokyogeiger.info/

[Andy Szymanski]

The peak releas at the plant of 400 milliseiverts (400,000 microseverts) was recorded in a single instant right next to the reactor.
The theory (corroborated by government sopkesperson Edano in his press conference) is that this reading came from a portion of the concrete outer building of the reactor that blew out from the explosion - it likely absorbed a much larger amount than anywhere else.

Fact remains that at MAX peak (approx 9:30 AM) the reading at the gate of the plant was 12 milliseverts (12,000 microseverts) at a location just tens of meters away from the reactor. These levels soon decreased (see Tepco graph).

This relationship seems important as it indicates that the 400 milliseivert reading was a very local phenomenon (within yards).

[Neago]

That chart (at tokyogeiger.info) is cut off around noon, at the peak of the radiation level.

Thanks for this collected info - very useful to pass on to family and friends. Also great updates by Roy at http://www.mutantfrog.com/2011/03/15/radiation-safety-update/

[MattAlt]

Thanks for the corrections, Mandy and others. Keep them coming and let me know if I implemented them correctly.

[Tioguerra]

Thanks for the article. I recommend being more specific here:
"That's something like three ten thousandths of a millisievert."
I recommend saying this instead:
"That's 0.0003 millisievert, or 1/3333 of a millisievert."

[MattAlt]

Paco, your link is a "snapshot" taken at noon. The one I link to is live, and shows a rapid drop-off to normal levels.

[Andy Szymanski]

Mandy is correct - the explanation is a bit confusing.

Matt, I would edit the explanation of "seiverts" to reflect that the unit is in itself only a measure of exposure - but it is important to note that all numbers that are reported (even the ones on NHK that don't have "pre hour" tacked on the end) are PER HOUR.

All radation numbers reported herein are in microseiverts/h or milliseiverts/h, not acute "instant" exposure numbers.

[Sarah]

Thank you so much for this. The panic is worse than the problem itself, and the misinformation is flying fast and furious. I'll be sure to link this to anyone worried about the reactors and the radioactive material.

[Andy Szymanski]

New info just coming in:

http://plixi.com/p/84148912

This link shows the readings at the front gate of the plant, tens of meters from the reactor.
As we can see, the reading has dropped to 489.8 microseiverts/h (0.4898 milliseiverts/h) by 4:30 PM.

Even at these readings, you would have to stand in front of the plant for 14 hours to absorb enough radiation to equal 1 chest CT scan.

All of this information available on Tepco's site - facts are your friend.

[Andy Szymanski]

CoCreatr, thank you for your information on the wind speeds. I had no idea how long it would actually take to reach Tokyo.

The graphs from the Hino site seemed to match the Tepco gate readings so well that I assumed they were from the same source - thank you for correcting this.

It seems that there were two major release events this morning - the one that happened very early this morning (which I believe was at the #2 reactor) and the fire at reactor #4 around 9:30 AM.

[Greenkiss]

There is also this live broadcast ''Geiger counter in Chiba'', 200km south of Fukushima Nuclear Plant :

http://ustream.tv/channel/geiger-counter-chiba

[MattAlt]

Updated to reflect comment suggestions.

[Ladyartemis 112]

I just wanted to say thank you for giving us these great facts. It really has helped me to deal with my decision to stay in Tokyo. I will send this to my family and I hope that they will calm down as well. Thanks again!

[PhilW]

Arr, so you are the source of the edited version I received by email, then condensed to a paragraph and posted my friends. Well done, at last a person with a scientific mind. These reporters cause a lot of worry with their latest 'big stories'.

[Daniel]

Interesting compilation of what is known. But that's not the main point in assessing a risk. The question is: What can you gain if you stay, and what can you loose.

I think it's a simple answer.

[samir]

If you have the opportunity, leave the country as quickly as
possible. If the authorities tell the truth, it's to late.

[Andy Szymanski]

Good news to report:

The radation levels at the two locations I mentioned in an earlier post have continued dropping.

As of 2 PM today, the reading in Iwaki City (40 kilometers from the reactor) has dropped to 1.5 microseiverts/h. It had reached a peak of 23.7 microseiverts/h at 4 AM.

Similarly, as of 5 PM today the reading at Tokai Village in Ibaraki (110 kilometers from the reactor) has dropped to 1.3 microseiverts/h. It had reached a peak of 5.8 microseiverts/h at 7:46 AM.

All good news.
Tokyo has returned to normal background levels as of 1:30 PM, but this shows a definite and steady drop in areas much closer to the reactors.

[MattAlt]

This wasn't written advocating anyone either stay or go, but rather to give people the information they need to make a decision based on the facts as they are currently known. If you use them to make either decision, more power to you.

Personally? I am staying. So my wife and her family. So is Andy. But everyone's situation is different.

[trad]

I think the key thing to watch is another explosion in #2. I understand its unclear what ignited explosion in #2 (and for that matter #1 and #3). Its supposed to be controlled environment and these explosions are not supposed to happen. Because the pressure shelter (where suppression chamber is located) is to protect in event of big meltdown, the outer containment layer for #2 is a huge line of defense. . If that goes, (or the same explosion that happened in pressure chamber in #2 happens in #1 or #3), then I think its real problematic. Good news is that things in #1 and #3 seem to be stabilizing. My fingers are crossed big time for #2.

[Aria Murasaka]

Brilliant explanation! Thanks for taking the time to research the facts and analyze them (something that many journalists seem unable to do, even though it should really be their job!)

I would hope that this gets translated in Japanese, or that someone talking the language would write something similar because from all the tweets I can read commenting the general nhk broadcast at least, there seems to be utter confusion, disbelieving and misunderstanding about where things stand right now

[Bill J.]

I don't recall who posted this pic, but it's a handy reference for exposure levels.

http://twitpic.com/49mm4l

[Andy Szymanski]

Additional coverage from NHK news.

Dr Nakagawa, professor from the Department of Medicine at Tokyo University (Japan's most prestigious public institution) has the follwing comments regarding the (extremely) low amounts of radiation detected within Tokyo city limits (0.809 microseiverts/h):

"I believe that this did indeed result from the escape of radiation at the Fukushima plant, and it is not surprising that it was detectable even here in Tokyo. That being said, the levels are extremely low and pose no risk to human health whatsoever. It is very difficut to imagine a scenario in which radiation [in Tokyo] will reach levels that could cause any health effects. I urge the public to be at ease."
(My translation)

I would like to point out that all of this information is ready available. The above quote and the levels measured in various locations quoted in my previous post are from this article:

http://www3.nhk.or.jp/news/html/20110315/k10014695401000.html

These facts (the descending levels and the medial advice) have been broadcast every hour om NHK live TV.
Perhaps this is why Japanese seem to be more calm than many foreign residents.

[Andy Szymanski]

Edit typos in above post:

"...pose NO risk to human health whatsover."

These facts (the descending levels and the MEDICAL advice) have been broadcast every hour on NHK live TV.

Apologies; typing quickly.

[samir]

most people can not choose, there are no true facts, they are all veiled. therefore, they are like 'Frogs in Water':

"if you put a frog in boiling hot water, it would jump out. But put it in cold water, and heat it up gradually, it would slowly boil to death…

[*]

I advise you to follow as well what the ASN (French Nuclear Authority). Criticality level rising to level 6.

See press release http://globz.org/tmp/asn.pdf

[David Cook]

Some hopefully useful articles:

http://www.theregister.co.uk/2011/03/14/fukushiima_analysis/

http://www.newscientist.com/blogs/shortsharpscience/2011/03/japan-megaquake-update.html

http://www.csmonitor.com/USA/2011/0314/Meltdown-101-What-is-a-nuclear-reactor-meltdown

http://m.ft.com/cms/s/0/32025c2a-4e6a-11e0-98eb-00144feab49a.html

http://bravenewclimate.com/2011/03/13/fukushima-simple-explanation/

[Vince]

Hey. I am in almost the same situation :)
I am leaving the 24th to japan from sweden.
You can read on my blog too.

myfeetinjapan.wordpress.com