NUCLEAR CALCULATIONS
5 rems is the annual legal dose to NUCLEAR WORKERS in the US (NOT the allowable annual dose to members of the PUBLIC).
IAEA recommendations are 2 rems per year legal limit for nuclear workers but US never adopted that.
NRC, EPA and DOE have different legal limits for doses to the public from the nuclear industry in addition to the background (natural and manmade).
EPA has the authority and responsibility to protect the public from radiation. NRC has authority onsite over its licensees. DOE is supposed to be subject to EPA.
NRC allows public exposures to individuals of 100 millirems per year from air and water (10 CFR 20) and more from sewage (10 CFR 20 appendix B).
NRC allows public exposures of 25, 100 or 500 millirems per year from a decommissioned nuclear facility (10 CFR 20 subpart E) depending on various conditions.
These are millirems EDE (effective dose equivalent) which actually have more radioactivity per millirem for many radionuclides than the previous definition of millirem.
EPA allows 25 millrems per year exposure to members of the public from each nuclear power reactor or fuel chain facility 40 CFR 190.
(This regulation is in the old millirems, not millirems EDE)
Under the Clean Air Act, in its NESHAPs regulations, EPA allows members of the public to be exposed to 10 millirems/year from air.
Under the Safe Drinking Water Act regulations, EPA allows public doses of approximately 4 – 15 millirems per year from water depending on the type of radionuclides giving the dose.
DOE allows 100 millirems (EDE) per year to members of the public. (DOE Order 5400.5)
Also
1000 millirems = 1 rem
1000 microrems = 1 millirem
10 microSieverts = 1 millirem
10 milliSieverts = 1 rem
50 milliSieverts = 5 rem
Rems, millirems, microrems, Sieverts, milliSieverts, microSieverts are calculated doses – damage to tissue from ionizing radiation. They supposedly take into account the energy of the impact from alpha, gamma, beta emissions from radionuclides. Since different radionuclides give off different combinations of alpha, beta and gamma rays (which can also have different characteristic energies), they cause different damage. (I have a hard time believing they can really know the damage from each of the hundreds of different kinds of radionuclides generated by nuclear energy.)
Each alpha, beta and gamma emission per second is a becquerel (Bq).
37 billion emissions per second (37 billion Bq) = 1 curie (ci)
You have to know if it is a curie of iodine 131 or of plutonium 239 or strontium 90 to calculate the dose (in rems or Sieverts).
When they are giving dose numbers like milliSieverts or millirems they must be assuming all the radioactivity being detected is from a given radionuclide—usually iodine-131 or cesium-137 and setting the detection instruments to convert from curies to millirems or from Bq to Sieverts. Most detectors only count gammas.
So the reported doses in milliSieverts (mSv) or millirems (mr) is just an estimate.
Further complication is the reality that there is a combination of radionuclides—never just iodine 131 or just cesium-137, so we are not hearing the full report.
Re the last point in the items below, it is the radionuclides (the radioactive atoms themselves) that can be inhaled or ingested and concentrate in tissues and organs—these then give off alpha, beta and/or gamma from within the body, giving a higher dose to the tissue nearby.
NIRS is preparing another radiation primer to be put on the website (www.nirs.org) in the next day or so.
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Thanks to NIRS for this important information. Keep on hand so you can figure out what the media are saying. Annual “allowable” dose: 50 microsieverts or 5 rem for members of the public; a bit more than double that for nuclear workers (about 100 milliSievert).
Curies and Becquerels are used to measure how much is in a given mass of a radionuclide or in concentrations of them in water or soil.
Rads, rems and Sieverts are used to measure doses received by people.
Extrapolating from Curies and Becquerels to received human doses is complicated. I hope to get information on this soon from a nuclear physicist.
Ingested radionuclides like alpha-emitting plutonium are hard to measure and impossible to remove.
Gamma radiation is whole body, like an X ray. At low doses it can go through you without hitting a cell or DNA (with luck). If it hits and kills a cell, the cell can’t become cancerous. If it survives…..
Beta and alpha particles are ingested and go to specific organs (strontium 90 to bone, cesium 137 to muscle, plutonium to lungs).
Radiation Measurement Units – International (SI) System
| The curie (Ci) is replaced by the becquerel (Bq)* 1 kilocurie (kCi) = 37 terabecquerel (TBq) 1 curie (Ci) = 37 gigabecquerel (GBq) 1 millicurie (mCi) = 37 megabecquerel (MBq) 1 microcurie (µCi) = 37 kilobecquerel (kBq) 1 nanocurie (nCi) = 37 becquerel (Bq) 1 picocurie (pCi) = 37 millibecquerel (mBq) |
Becquerel (Bq)* replaces the curie (Ci) 1 terabecquerel (TBq) ~ 27 curie (Ci) 1 gigabecquerel (GBq) ~ 27 millicurie (mCi) 1 megabecquerel (MBq) ~ 27 microcurie (µCi) 1 kilobecquerel (kBq) ~ 27 nanocurie (nCi) 1 becquerel (Bq) ~ 27 picocurie (pCi) * 1 Bq = 1s-1 |
| The rad (rad) is replaced by the gray (Gy) 1 kilorad (krad) = 10 gray (Gy) 1 rad (rad) = 10 milligray (mGy) 1 millirad (mrad) = 10 microgray (µGy) 1 microrad (µrad) = 10 nanogray (nGy) |
The gray (Gy) replaces the rad (rad) 1 gray (Gy) =100 rad (rad) 1 milligray (mGy) = 100 millirad (mrad) 1 microgray (µGy) = 100 microrad (µrad) 1 nanogray (nGy) = 100 nanorad (nrad) |
| The roentgen (R) is replaced by coulomb/kg (C/kg) 1 kiloroentgen (kR) ~ 258 millicoulomb/kg (mC/kg) 1 roentgen (R) ~ 258 microcoulomb/kg (µC/kg) 1 milliroentgen (mR) ~ 258 nanocoulomb/kg (nC/kg) 1 microroentgen (µR) ~ 258 picocoulomb/kg (pC/kg) |
Coulomb/kg (C/kg) replaces the roentgen (R) 1 coulomb/kg (C/kg) ~ 3876 roentgen (R) 1 millicoulomb/kg (mC/kg) ~ 3876 milliroentgen (mR) 1 microcoulomb/kg (µC/kg) ~ 3876 microroentgen (µR) 1 nanocoulomb/kg (nC/kg) ~ 3876 nanoroentgen (nR) |
| The rem (rem) is replaced by the sievert (Sv) 1 kilorem (krem) = 10 sievert (Sv) 1 rem (rem) = 10 millisievert (mSv) 1 millirem (mrem) = 10 microsievert (µSv) 1 microrem (µrem) = 10 nanosievert (nSv) |
The sievert (Sv) replaces the rem (rem) 1 sievert (Sv) = 100 rem (rem) 1 millisievert (mSv) = 100 millirem (mrem) 1 microsievert (µSv) = 100 microrem (µrem) 1 nanosievert (nSv) = 100 nanorem (nrem) |
Above table reproduced here courtesy of Health Canada
SI Prefixes For Multiples And Submultiples Of SI Units
| yotta (Y) 1,000,000,000,000,000,000,000,000 = 10^24 = 1 septillion
zetta (Z) 1,000,000,000,000,000,000,000 = 10^21 = 1 sextillion exa (E) 1,000,000,000,000,000,000 = 10^18 = 1 quintillion |
Downloads for more information on the International System Of Units
The International System of Units (SI) 7th Edition – 1998
From: Bureau International des Poids et Mesures
Available here in Adobe® PDF Format – English Version
Supplement 2000: Addenda and Corrigenda to the 7th Edition -1998
From: Bureau International des Poids et Mesures
Available here in Adobe® PDF Format – English & French Versions
Guide For The Use Of The International System Of Units (SI)
NIST Special Publication 811 – 1995 Edition
Available here in Adobe® PDF Format
