We are hearing that due to leakage of nuclear power in Japan have detected traces of the radioisotope iodine-131 in Tokyo tap water at concentrations above the legal limit. It banned the consumption of water to drink and bottled water is recommended them. This has caused great alarm in the world and not only in Japan though the Japanese authorities insisted there was worrisome. Let's see if they were right or not: The analysis of Tokyo threw water activity values \u200b\u200bdue to iodine-131 between 150 and 210 becquerels per liter in water. A Becquerel (Bq) is a measure of radioactivity whose magnitude is equal to one disintegration per second. That is, in one liter of water from Tokyo, on Tuesday, disintegrated between 150 and 210 Iodine-131 nuclei per second. Is this worrying? English law and assume that the Japanese will be similar in the Royal Decree 783/2001, approving the regulation on health protection against ionizing radiation, is to establish standards for the protection of workers and members the public against the dangers arising from ionizing radiation. In this royal decree establishing alia dose coefficients for ingestion for each of the radioisotopes. (Is Peden available at this enalce BOE, Annex II) http://www.insht.es/InshtWeb/Contenidos/Normativa/TextosLegales/RD/2001/783_01/PDFs/realdecreto7832001de6dejulioporelqueseapruebaelregla.pdf
If we in the table we are interested in the isotope, Iodine-131 (I-131). We see it has a half-life of 8.04 days and that, like the rest of the isotopes, the dose depends on the age of that drink water (or food) containing such isotopes. For an adult over 17 years, the conversion factor is 2.2 • 10-8 (0.000000022) Sv Bq. That is, each Bq of Iodine-131 that you will eat a 0.000000022 radiation dose Sv, or what is the same military 0.000022 Sv This figure multiplied by 210 gives us the amount of Sievert per liter of water, giving a total of 0.00462 mSv / liter The sievert ( symbol Sv) is an SI derived unit that measures radiation dose absorbed by living matter, corrected for possible biological effects.
This unit gives a numerical value that can quantify the effects of ionizing radiation.
Symptoms in humans due to radiation accumulated during a day starting from 250 mSv.
short, and not bore you with calculations, adult would need to drink 54,112 liters of water to achieve the recommended limit. If you drink 2 liters a day would need 70 years to be drinking water that pose a risk. In the case of children and looking at the conversion factors table would leave us so much younger that the recommendation not to drink was made for them but for safety.
Today the dose has dropped to levels not of concern.
Another point to consider is the half-life of iodine 133 that is 8.04 days ie within 8 days would be half past 16 a quarter, ie that after several months would have reduced per thousand.
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