radioactivity

Radioactive pollution

Chernobyl and Fukushima show that nuclear energy cannot be safely controlled. Due to various natural events or terrorist attacks, Chernobyl and Fukushima can be repeated anytime and anywhere in the world.

Since there are different physical quantities in the field of ionizing radiation, a brief overview of the measured quantities of radiation is given:

activity

Activity is the number of decay events per unit of time that occur in a sample of a radioactive or radioactively contaminated substance. The activity is usually given in the SI unit Becquerel (Bq), one Becquerel corresponds to one decay per second.
Bq = 1s -1 or (T to the power of minus 1).

The equivalent dose can be approximately determined by means of a dose conversion factor.

Units and measurement

The “half-life” stands for the time in which half of a radiating substance has decayed.
Radioactive elements always behave in the same way: the half-life of 230 plutonium is 24,110 years, but there are also plutonium isotopes with half-lives of days or months. In contrast, with 131-iodine, which is used in medicine, it only takes a little more than eight days for half of it to break down.

The unit of gray (Gy) indicates the absorbed dose of ionizing radiation, for example also in the case of medical radiation. 1G = 1J / kg.
This is not to be confused with information in the unit Sievert (Sv). Here, too, the absorbed dose is meant by ionizing radiation. To calculate the effects of radiation on living organisms, this unit combines the dose with guide values for tissue sensitivity. For this purpose, a radiation weighting factor Wr is introduced. This is determined for each organ or tissue by the International Commission on Radiological Protection (www.icrp.org). One also speaks of the effective dose and the organ dose. In Sievert, experts therefore state the radiation exposure from background radiation from the environment or from radiation accidents.

1Sv = 1 J/kg.

Radiation weighting factor Wr for some types of radiation:

RADIATION TYPE WICHTUNGSFACTOR WR
X-ray and gamma radiation 1
Beta radiation 1
Slow neutrons 5
Fast neutrons 10
Alpha radiation 20
Heavy ions 20

The previously common units Rem and Rad (replaced by Sievert) are no longer used
1 rem = 0.01 Sv = 10 mSv. Wheel replaced by Gray.

Ionizing radiation: what does it do in the body?

All biological molecules and also the water contained in the body slow down radiation. This releases energy. It is responsible for the effect of ionizing radiation and also triggers the change in the charge of atoms and molecules already described in living tissue.
The resulting ions are particularly reactive. They immediately try to enter into chemically stable bonds again - not always those that make sense or are “right” for the body.
For example, ionizing radiation can render important enzymes inoperable or destroy cell components and lead to cell death. However, it can also cause changes in the large molecules of the genetic material DNA, which are passed on to daughter cells during the next cell division and contribute to the development of cancer in the long term.

Healthy cells are able to repair a lot of damage or specifically break down damaged structures. If the radiation dose is very high or the affected tissue is particularly sensitive, this natural protection is no longer effective. In principle, however, the following applies: Even a very low dose of radiation can, under unfavorable circumstances, be sufficient to destroy tissue or initiate tumor development.

There is no lower limit or threshold below which ionizing radiation would be harmless.

The natural radiation exposure can serve as a comparison for assessing a radiation risk. In Germany, their equivalent dose H is in the order of 1-2 mSv per year. The following limit values apply to Germany (in addition to natural radiation):

SAFE DOSE PERFORMANCE ENTRY VALUE FOR LONG-TERM RELOCATION
1 mSv (1,000 µSv) per year 100 mSv (100,000 µSv) per year
0.02 mSv (20 µSv) per week 2 mSv (2,000 µSv) per week
0.003 mSv (3 µSv) per Tag 0.3 mSv (300 µSv) per day
0.0001 mSv (0.1 µSV) per hour 0.01 mSv (10µSv) per hour

Clinical symptoms of radiation sickness

150 mSv (150,000 µSv) as an integrated dose.
The maximum permitted annual dose for occupationally exposed persons is 20 mSv, but no more than 400 mSv may accumulate over one working life. For the normal population it is 1 mSv (without natural radiation and medical measures). An unborn child must not receive a radiation dose higher than 1mSv until it is born.

Radioactive particles

In the past, nuclear weapon tests and reactor accidents resulted in some considerable releases of radioactive particles. The problem with these radioactive particles is the radiation duration, which is indicated by the half-life (HWZ) and states in which time the radiation energy has fallen by half. It also defines how and where these particles are absorbed in the body and how the radiation subsequently causes them. These are essentially:

Iodine 131: HWZ: 8 days Storage in the thyroid gland; can lead to thyroid cancer and other thyroid dysfunction.
Cesium 137: HWZ: 30 years Storage in all organs; is considered a cancer trigger; is absorbed through the food chain.
Strontium 90: HWZ: 28 years Storage in teeth and bones; is considered to be a trigger for leukemia.
Plutonium 239: HWZ 24,000 years Danger to groundwater; highly toxic, is considered a strong cancer trigger.

Consequences of low radiation:

Recent studies on low radiation showed:
- genomic instability
- genetic mutations
- frequent malformations
- cell aging
- Various non-cancer diseases

The following table shows which stresses we are exposed to and which medical consequences can be expected:

Comparison of radiation values in millisieverts (mSv)

1.015 mSv
First officially measured value at the accident reactor Fukushima 1 on Friday, March 11th

1.2 mSv
Approximate radiation dose when x-raying the spine (per examination)

2.1 mSv
Average annual dose according to the Federal Office for Radiation Protection

2.4 mSv
Average annual dose according to the UN report

10 mSv
Approximate radiation dose from full-body computed tomography (per examination)

100 mSv
Annual dose that can cause cancer in one percent of those exposed

250 mSv
Radiation dose that, if it acts on the body in a short period of time, causes acute radiation sickness (nausea, vomiting, headache, etc.)

400 mSv
Radiation dose per hour at the damaged Fukushima 1 power plant on Tuesday morning, March 15th

4000 mSv *
Lethal dose of radiation if absorbed in a short period of time.

* Mortality of 50 percent, 7000 mSv are certainly fatal. In 1986, 47 employees of the rescue teams who were working directly on the damaged Ukrainian reactor in Chernobyl died. They were irradiated with 6000 mSv.

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