Title says it all--two notes written by Frank Sanns and three "Q&A sessions" copy and pasted from TRL Facebook community page. This post will cover the following:
- Calculating Internal Dose Rate Exposure from Consuming 1kg of Food Containing 30Bq/kg of Caesium-137 per day (4/25)
- First Phase of Crisis Ends (4/21)
- Q: What affect is the radiation having in the ocean? Didn't they use ocean water to cool the reactors? Did they pump that water back into the ocean? If so, how will that affect the wildlife?
- Q: Hi Frank, just interested in your thoughts on the effects of the total radiation load on the ocean in the vicinity of the reactors. Alarming levels are being reported at the moment from outside the
For more notes written by Frank Sanns, click here.
Here we go.
4/25
Calculating Internal Dose Rate Exposure from Consuming 1kg of Food Containing 30Bq/kg of Caesium-137 per day
It may be illustrative to look at the very worst case scenario of exposure and that would be infinite biological and radiological half lives. Also include in the assumption that an entire Kg containing 30 Bq would be consumed each day and the isotope would be Cs-137 which is important for gamma energy for conversion to dose rate.
The next assumption would be of the geometry of the human body. Worst case would be a sphere. This minimizes the distance from the emitting particle to the entire body. Next we use a 60 kg body with a density of 1 so that would be a sphere 23.5 cm in radius and we will use this radius as the average distance to the particle of radiation but it also could be argued that 11.75 cm is appropriate. Mathematical integration should be used but for this approximation it is an appropriate value. Using the 30 Bq per kg of food, that gives an estimated average gamma internal dose rate for the entire body of 0.000043 microSv/hr.
Eating food with 30 Bq of cesium-137 activity would increase each day as the isotope concentration increased in the body since our assumption was no biological or radiological elimination. In this absolute worse case scenario, the dose rate would be 0.000043 microSv/hr the first day, 0.000086 microSv/hr the second day, 0.000172 micro Sv/hr the third day and so on. After a month of consuming a Kg of 30 Bq of Cesium-137 you would be having an internal dose rate of 0.00129 microSv/hr. This is one hundredth of the normal background of Tokyo
Another way to look at it is 30 Bq x 365 days= 10,950 Bq intake for the year. If you want to calculate this on your own there is an online calculator at: http://www.radprocalculator.com/Gamma.aspx Use whatever distance you feel for your calculation but a distance of 12- 23.5 cm will give you the effective average distance from the emitter for the worst case spherical body estimation.
The vegetables that will coming to market now, will not have surface contamination with radioactive elements. The time for that has past. I can not speak for plants harvested from some areas during March and very early April because that was the peak of the fallout. There should be good documentation on what areas are suitable for farming and which are not and that should be getting better each day. We are now getting into the long term phase of establishing these safe and not so safe regions. I would still be looking at the map here to make a judgement: http://www.slideshare.net/energy/radiation-monitoring-data-from-fukushima-area-04072011 Green, yellow and orange would be the higher risk compared to other regions for growing.
4/21: First Phase of Crisis Ends
I would like to declare an un-official end to the first phase of the nuclear crisis in Tokyo Tokyo
The heat being generated by what is left in the reactors is a minute fraction of what was being produced in March and the dangers have fallen a hundredfold or more. There is still a very small risk that something unexpected will happen at the plant but short of some other catastrophe or some other unforeseen development, breath easier today. The next important information will be on the long term levels of radiation in the soil for food growing as air levels are now essentially a non-issue. Really good news I would say after all that the people of Tokyo
Q: What affect is the radiation having in the ocean? Didn't they use ocean water to cool the reactors? Did they pump that water back into the ocean? If so, how will that affect the wildlife?
These particular reactors use the same water to generate steam as they use to cool the reactor. In these kinds of reactors, the large pipes that carry the steam from the core of the reactor pass through the steel reactor pressure vessel and they also pass through the OUTER containment concrete structure and to a nearby turbine/generator to make electricity. The same water is then returned to the reactor through more pipes that go through the outer containment and back through the inner containment again to the core. Any break or fissure that occurs in these pipes can create at direct leak to the outside air. These are potential weak links in large earthquakes and in explosions with certain characteristics. Concrete is brittle compared to steel so I suspect earthquakes have and are opening up cracks that are letting water leak to places that it should not be leaking. It makes stopping the flow of cooling water from the reactor difficult to entirely contain and this is why I think there are continued surges in radiation in the ocean waters adjacent to the reactors. Water is used as a shield in some reactors and in all spent fuel pools because is shields the radiation so well. A fish swimming 25 feet from the core of the reactor would not hardly get any radiation at all. A person 250 feet from an exposed core in air would die quickly of radiation effects. The danger in the ocean is when wildlife comes in direct contact with high level water and that is not good. There are most likely negative effects going on to the wildlife just off the coast of the reactors and will continue for some time yet. The ocean is large and the radiation quickly dilutes. In the long term mother nature has great recovery powers so there should be no longterm effects.
4/1
Q: Hi , Frank, just interested in your thoughts on the effects of the total radiation load on the ocean in the vicinity of the reactors. Alarming levels are being reported at the moment from outside the Fukushima
Frank Sanns Recovery of a brief excursion into the ecosystem is not much of a concern. Longer excursions or extremely intense ones are more problematic. There will be radioactive plankton and fishes that will be eaten by larger fish that have larger migratory patterns. The levels are ultra high at the moment and will continue upward. This sea life will find its way into the human food supply and unsuspecting people will eat it. There also is the chance for genetic mutations that can affect entire species of ocean and bird life. It is not doomsday but it is sure playing Russian Roulette with the planet.
Dale There has been a discussion on the IAEA Briefing page on options for storing the contaminated water temporarily 1. You could mix in sawdust with the rad water, freeze it, and offload the icecube in Antartica! The addition of sawdust makes the ice tougher than steel and maybe converting the water to icecrete would minimize the spill risk and make it boyant 2. They are now negotiating with the US to pump radioactive water into the barges after the fresh water is removed http://www3.nhk.or.jp/daily/english/02_04.html Just intererested in your thoughts here Frank, do either of these ideas have any merit rather than contaminating the ocean?
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