Radiation
Radiation surrounds us. Detectable amounts occur naturally in soil, rocks, water, air, and vegetation but large dosages can have dramatic and life changing effects. There are different kinds of radiation but it is ionising radiation that can cause damage to living tissue at high levels making it vital to control our exposure to it.
Radiation exposure depends on three factors, the:
- strength of the radiation source
- distance you are from it
- duration of the exposure
Exposure to high levels of ionising radiation can result in mutation, radiation sickness, cancer, and death but when used in medical applications it can be used to prolong life. Ionizing radiation is invisible and not directly detectable by human senses, unless at very high doses, so instruments such as Geiger counters are necessary to detect its presence.
Measurement
One way to measure radiation is to measure the dose of radiation received, i.e. the effect it has on human tissue, which is measured in sieverts, abbreviated as Sv.
As 1 sievert represents a very large dose the following smaller units are commonly used;
- Millisieverts, one thousandth of a sievert and abbreviated as mSv (1000mSv = 1Sv)
Or
- Microsieverts, one millionth of a sievert and abbreviated as uSv (1,000,000uSv = 1Sv)
Dosimeters generally measure in microsieverts.
An older unit for dose is the rem (Roentgen Equivalent in Man), or the smaller millirem (abbreviated “mrem”) still often used in the United States. One sievert is equal to 100rem.
Roentgen’s are another measure, 1 Roentgen (R) equals 0.877 rem or 0.00877 Sieverts.
Levels of radiation at Chernobyl
Immediately after the explosion
The radiation levels in the worst-hit areas of the reactor building, including the control room, have been estimated at 300Sv/hr, (300,000mSv/hr) providing a fatal dose in just over a minute.
The reactor staff struggled to establish the levels of radiation following the explosion as one dosimeter capable of measuring up to 9Sv per second 1,000 R/s was buried in the wreckage, and another one failed when it was turned on. All the remaining dosimeters had limits of 0.001 R/s (0.3 µA/kg) 30mSv/hr and read “off scale”. The reactor staff could therefore only ascertain that the radiation levels were somewhere above 30mSv/h while in reality the true levels were far higher.
| Location | uSv/hour |
|---|---|
| “Lazurny” swimming pool | 0.9 |
| Pripyat kindergarten “Golden Key” | 0.8 |
| Zone checkpoint | 0.3 |
| Pripyat 1970 monument | 11.5 |
| Pripyat checkpoint | 0.6 |
| Hospital No 126 | 0.7 above ground 0.8 – 382+ in the basement |
| Palace of culture | 0.8 |
| Pripyat fairground | 1.3 |
| Middle School Number 3 | 0.7 |
| Middle School Number 1 | 0.7 |
| Reactor 4/5 | 0.3 |
| Cooling towers | 1.5 Inside 12.6 to the rear |
| 16 storey tower block | 0.9 roof |
| Duga-3 array | 0.5 |
| Fish laboratory | 1.6 outside 0.7 inside 1.3 by the fire engine |
| Jupiter factory | 0.5 outside 0.7 – 1.6 inside |
| Police station | 0.7 |
| Vehicle dump | 1.6 |
| Yanov Railway Station | 0.3 |
| Dock cranes | 0.7 |
| Reactor 4 | 2.4 – 2.6 surrounding roads |
| Pripyat cemetery | 14 – 22 |
| Chernobyl cemetery | 0.2 |
| Abandoned village | 0.3 |
| Residential houses Chernobyl | 0.2 |
| Cafe Pripyat | 13.6 on steps |
| Metal claw used in the clean up | 336 |
