Supernova remnants

Man is exposed to different kind of natural occurring Man is exposed to different kind of natural occurring radiation. That includes radiation from outer space as well as radiation. That includes radiation from outer space as well as radiation from natural sources on earth.radiation from natural sources on earth.

Outer space originated Outer space originated radiation is mainly absorbed by the radiation is mainly absorbed by the atmosphere.atmosphere.

Ultraviolet (UV) radiation in the sunlight Ultraviolet (UV) radiation in the sunlight as part of the solar spectrumas part of the solar spectrum

Cosmic Rays are high energetic Cosmic Rays are high energetic particles, originated in the solarparticles, originated in the solarflares at the surface of stars or in flares at the surface of stars or in supernova explosions over the supernova explosions over the lifetime of our galaxy.lifetime of our galaxy.

Sources of natural terrestrial radioactivitySources of natural terrestrial radioactivity

Radioactivity originating from the natural decay chains, Radioactivity originating from the natural decay chains, long lived long lived -emitters. -emitters.

There are four natural decay chains:There are four natural decay chains:

Uranium series: Uranium series: 2382389292U U 206206

8282PbPb

Actinium seriesActinium series : : 2352359292U U 207207

8282PbPb

Thorium seriesThorium series : : 2322329090Th Th 208208

8282PbPb

Neptunium seriesNeptunium series : : 2412419494Pu Pu 209209

8282PbPb

There are several long-lived members of the decay chain. The resulting radioactivity is found in natural environment, but particularly enriched in uranium and radium quarries.

Particularly important is the noble gas radon-222 Particularly important is the noble gas radon-222 2222228686Rn, Rn,

which is a member of the uranium series.which is a member of the uranium series.

It decays by It decays by -emission-emission with a half life of with a half life of tt1/21/2=3.82=3.82

days. Because of its gaseous character it can diffuse out of days. Because of its gaseous character it can diffuse out of the rock and mix into the air where it can be inhaled. the rock and mix into the air where it can be inhaled. Outside its concentration is low because of the dilution in Outside its concentration is low because of the dilution in air, but in closed rooms like basements its concentration air, but in closed rooms like basements its concentration can be quite large.can be quite large.

Once inhaled, the majority of the dose is Once inhaled, the majority of the dose is deposited in the trachea-bronchial region by the decay of deposited in the trachea-bronchial region by the decay of the short-lived daughters, the short-lived daughters, 218218PoPo and and 214214PoPo, which are both , which are both -emitters-emitters..

The radon-problem is therefore mainly due to -bombardment of sensitive lung tissue, which can cause cancer.

The second largest source for natural background activity The second largest source for natural background activity comes from the long-lived radioisotope comes from the long-lived radioisotope 4040K.K.

half life of thalf life of t1/21/2 = 1.28 = 1.28 101099 years. years.

natural isotopic abundance is natural isotopic abundance is 0.0118 %.0.0118 %.

It decays by It decays by decay, Edecay, E 1.3 1.3

MeV (89%) and by MeV (89%) and by -decay, E-decay, E

= 1.46 MeV (11 %).= 1.46 MeV (11 %).

This isotope is a strong source for natural internal and external This isotope is a strong source for natural internal and external radiation exposure, since potassium is a natural constituent for body radiation exposure, since potassium is a natural constituent for body tissue like skeletal muscles and bones. It is also an important regulator for tissue like skeletal muscles and bones. It is also an important regulator for cell processes (see information transfer in nerve cells). In addition K is cell processes (see information transfer in nerve cells). In addition K is also frequent in external materials as stone or concrete.also frequent in external materials as stone or concrete.

NN 0.000118 0.0001180.00030.000380 kg = 0.00294 g.80 kg = 0.00294 g.40 g = 6.02240 g = 6.02210102323 atoms atomsNN 4.44 4.4410101919 4040K atoms K atoms in the whole body: in the whole body: AA 2.44 2.4410101010 decays/yr decays/yr

The whole body activity on 40K is:The whole body activity on 40K is:

A(A(4040K) = K) = N N = = 5.45.41010-10-10 [1/yr] N [1/yr] N 0.03% of the body 0.03% of the body material is kalium (25 g potassium).material is kalium (25 g potassium).

Therefore the natural abundance of 40K in body tissue is:Therefore the natural abundance of 40K in body tissue is:

This corresponds to a whole body activity of A This corresponds to a whole body activity of A 764 Bq 764 Bq

Assuming that the entire radiation is absorbed in the body tissue, the Assuming that the entire radiation is absorbed in the body tissue, the whole body exposure is: whole body exposure is: ERER ( A ( A 0.8 MeV) / 80 kg = 4 0.8 MeV) / 80 kg = 4 1.6 1.6 1010-15-15 J/kg = 3.8 J/kg = 3.8 1010-5-5 J/(kg J/(kg yr) = 3.80 yr) = 3.80 1010-5-5 Gy/yr = 38 mrad/yr Gy/yr = 38 mrad/yr

With an quality factor of With an quality factor of Q Q 1 1 the equivalent dose rate the equivalent dose rate DR DR is: is:

DR DR 38 mrem/year 38 mrem/year

The external dose from 40K is in the same order of magnitude 28 mrem/yr.

There is considerable exposure due to artificially produced sources!

Possibly largest contributor is tobacco which Possibly largest contributor is tobacco which contains radioactive contains radioactive 210210PoPo which emits 5.3 MeV which emits 5.3 MeV particles particles with an half life of with an half life of TT1/21/2=138.4days=138.4days..

During smoking process During smoking process 210210Po is absorbed by the bronchial systemPo is absorbed by the bronchial system

Lungs are exposed to radiation!

Only estimates are available which suggest that smokers Only estimates are available which suggest that smokers receive an equivalent dose rate of: receive an equivalent dose rate of: HRHRTT=16 rem/y = 160 mSv/year=16 rem/y = 160 mSv/year

Using the lung tissue weighting factor Using the lung tissue weighting factor TT==0.120.12::

the total effective dose rate will be the total effective dose rate will be HRHR=1.9 rem/y =19 mSv/y=1.9 rem/y =19 mSv/y

Averaged over the entire smoking and nonsmoking US population this yields an annual effective dose of 280 mrem =2.8 mSv!

The other considerableThe other considerable exposureexposure sources are:sources are:

• fall-out from nuclear bomb testing between 1945 - 1980 (fall-out from nuclear bomb testing between 1945 - 1980 (1mrem/yr)1mrem/yr)

• nuclear power plants and nuclear laboratories (w 0.05 mrem/yr)nuclear power plants and nuclear laboratories (w 0.05 mrem/yr)

• inhaling radioactivity while smoking ( inhaling radioactivity while smoking ( 200 - 300 mrem/yr average) 200 - 300 mrem/yr average)

Often mentioned contributor to man-made radiation exposure is the fall-out from the 450 thermonuclear born tests performed between 1945 and 1980 (test ban).

Other products are Other products are 33H (12 y), H (12 y), 5454Mn Mn (312 d), (312 d), 136136Cs (13 d), Cs (13 d), 137137Cs (30 y) Cs (30 y) relatively relatively short-lived products in comparison with short-lived products in comparison with 1414C .C .Large fraction has since decayed.Large fraction has since decayed.

Main fall out product is Main fall out product is 1414C (70%) with TC (70%) with T1/21/2= 5730 y= 5730 y

Today's average effective dose 1 mrem = 10Sv

Estimated Average Total Effective Dose Rate in the United Estimated Average Total Effective Dose Rate in the United States from Various Sources of Natural Background RadiationStates from Various Sources of Natural Background Radiation