Sunday, June 24, 2012

What is the “safe” level of radiation?


Public dose limits for exposure from uranium mining or nuclear plants are usually set at 1 mSv per year above background.

The figures below are given by the National Council on Radiation Protection and Measurement (NCRP) and its international counterpart, the International Commission on Radiological Protection (ICRP). Both of these organizations offer recommendations for the maximum permissible dose (MPD) of radiation. 

General Public annual MPD by both NCRP and ICRP is 1 mSv.

For Radiation Workers, the annual MPD is 50 mSv (NCRP) and 20 mSv (ICRP), with a cumulative MPD of 10 mSv x Age.

MPD during pregnancy is 5 mSv (NCRP) and 2 mSv (ICRP).

However, experts including Professor Wade Allison of Oxford University argue that the dose limit can safely be raised to 100 millisieverts, based on current health statistics.

Compare this with the dose of 0.002 millisieverts/year of exposure for people living within 1 km of the Lynas plant in the worst case scenario (estimated by Lynas).

This level of 0.002 mSv/yr is actually grossly overestimated because the low energy gamma rays from the Thorium-232 decay chain is able to travel less than 300 metres in air.

Note, the average energy of most abundant emission is only 0.059 MeV, though the gamma ray from Thallium-208 decay to stable Lead-208 has a higher energy of 2.62 MeV.

The radon-220 has a very short half life of only 55 seconds and as such cannot travel far and do not accumulate in confined spaces like the radon-222 from the Uranium decay series.

So the actual radiation dose at a distance greater than 300 metres from the plant is approaching 0 mSv/year !
Comparative Dosages in Biological Effect in mSv.
Dose from natural radiation in the human body: 0.40 mSv per year
Sleeping next to someone for 8 hours 0.02 mSv/yr (10x Lynas worst case)
Sleeping in wooden house = 0.20 mSv/yr (100x Lynas worst case)
Smoking a pack of cigarettes daily 0.20 mSv/yr (100x Lynas worst case)
Slag brick and granite house = up to 2.0 mSv/yr (1,000x Lynas worst case)
Chest X-ray = 0.10 mSv
Medical or dental X-ray 0.39 mSv
CT Scan (Chest) = 10 mSv
CT Fluoroscopy of abdomen and pelvis 6 to 90 mSv (median=31 mSv)
Average individual background radiation dose: 2 mSv per year (1.5 mSv per
year for Australians and 3.0 mSv per year for Americans)
Dose from atmospheric sources (mostly radon): 2 mSv per year
Total average radiation dose for Americans: 6.2 mSv per year
Current average dose limit for nuclear workers: 20 mSv per year
Dose from background radiation in parts of Iran, India and Europe: 50 mSv per year
(Source: UNSCEAR and EPA and IAEA)

All the potassium that we eat everyday in our food contains potassium-40 and the normal dietary potassium would give a total of about 80 Bq per day.
Compare this with the Lynas waste which produces only 6 Bq/gm

Even your wife or husband is radioactive, with a radioactivity of 4,000 Bq from Potassium-40 and another 3,000 Bq from Carbon-14 giving a total of about 7,000 Bq!

Sleeping next to someone (i.e. your wife or husband) for 8 hours a day will lead to an exposure of 0.02 mSv/year (Source: UNSCEAR and EPA).

Since all living cells contain potassium, all types of meat, flesh, fruits, nuts and vegetables are radioactive because of the potassium-40 content.

The so-called sodium free salt recommended by health experts to combat high blood pressure is nothing more than just highly radioactive potassium salt! Even a lot of doctors, specialists and professors do not know this!

The message here is that more radioactive substances are freely sold in the shops and used as a fertilizer or eaten by us than you would otherwise thought.

Dr. Gary H. Kramer, who is the Head of the National Internal Radiation Assessment Section at Health Canada:
“Potassium chloride can be found in large quantities in stores selling materials for water treatment. The potassium content is about 500 g kg- Typically, the material is sold in 20 kg bags so each bag contains ~600 kBq of 40K giving a concentration of 30 Bq g-1. This is well above the exclusion level yet the material is handled as non-radioactive. The external dose rate in close proximity to a typical display in these types of shops would be about 150 microSv hr-1. A worker would only need to be near the pile for about 7 hours to exceed the public dose limit of 1 mSv.”

Nick Tsurikov, radiation safety expert:
"In most countries, the current maximum permissible dose to radiation workers is 20 mSv per year averaged over five years, with a maximum of 50 mSv in any one year.
This is over and above background exposure, and excludes medical exposure. The value originates from the International Commission on Radiological Protection (ICRP), and is coupled with the requirement to keep exposure as low as reasonably achievable (ALARA) — taking into account social and economic factors."

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