Living With Radiation (PHYSICS)

LIVING WITHRADIATION

All life forms on Earth developed and evolved in the presence of radiation. You may live very far from a nuclear reactor, yet you receive as much radiation as people living next to one, and here’s why.

13% cosmic rays

10.4% annual average exposureVia medical treatment

2.6% manufactured radiation

59% terrestrial radiation (inhaled)

15% terrestrial radiation (ingested)

Around 87% of the radiation dose is received each year comes from natural sources. Physicists believe that ever since the Earth was formed millions of years ago, the Earth and its inhabitants, have been bombarded with cosmic and terrestrial radiation. Cosmic radiation results from the interaction of Cosmic rays with the upper layer of Earth’ atmosphere. On the otherhand, terrestrial radiation is due to the presence of highly radioactive substances rising the Earth’s surface from the crust.

We are also irradiated from inside our bodies. Many of the foods we eat, like bananas, contain Potassium. Potassium is one the essential elements in our body, yet when we eat Potassium-rich foods we also ingests tiny amounts of the radioactive Potassium- 40. remember also that the foods we eat contain Carbon. Carbon has a radioactive isotope- Carbon-14.

DETECTING

RADIATION

Unlike visible light, the presence of radioactive substances within and around us cannot be detected by our senses. There are instruments that can be used to detect the-the most common of which is the GEIGER COUNTER. A GEIGER COUNTER consists of a detecting tube, an amplifier, and a counter. Nuclear radiation entering via the micawindow ionizes gases in the detecting tube. Charged particles eventually reach the electrodes and produce a very small current the is amplified and heard as click and pulses.

GEIGER COUNTER

Becquerel used the blackening of a photographic plate to detect the presence of nuclear radiation. This is the same principle being applied to the film badge used by radiation workers. A newer method of detecting radiation is with the used of the thermoluminescent dosimeter or TLD. TLD’s are also used in environmental monitoring studies where level’s of radiation are measured.

UNITS FOR

MEASURING

RADIATION

Our bodies are unable to sense the presence of radiation thus we may have received a lethal dose but without special equipment we will not be able to tell how much we received. We use different units of measure to describe quantities in radiation. For instance, the strength of any given radioactive source is indicated by its activity. The activity is defined as the number of nuclei which decays or disintegrates each second. The unit of activity is Becquerel (Bq), where 1Bq=1 disintegration/second.

The radioactive source may have a very high activity but not all the radiation emitted will not end up at the target area. Recall that some of the emissions may even be stopped by air or paper. To indicate how energy was received and absorbed by the target, we use a quantity called Radiation Dose. The Radiation Dose is a measure of the amount of energy absorbed per kilogram of an irradiated object at the actual target size. The unit of Radiation Dose is Gray(Gy) where 1Gy=1Joule/kilogram.

To define standards for protecting humans against Lethal doses of radiation, a measure of the biological effects of different kinds of radiations is required. Beta (ß) and Gamma (γ) rays are highly penetrating and can deposit their energy over a very long path. However, very little energy is deposited over any small interval, say, a typicall human cell. Alpha (α) particles on the other hand, lose their energy more rapidly and deposit essentially all of their energy over the very shor path length. The probability that a cell maybe damaged is thus far greater from a 1 gray of a radiation than from 1 gray of either Beta and Gamma radiation. To qualify these difference, the quality factor (QF) is used. The quality factor is a form of weighting.

Radiation Quality Factor

X-rays, Beta, Gamma 1

Low energy neutrons 2 to 5

Energetic neutrons 5 to 10

Alpha particles 20

The effect of a certain form of radiation on any biological system is thus dependent on the dose and on the quality factor. The product of these two quantities is called the dose equivalent, where:Dose equivalent=absorbed dose * quality factor

PEOPLE AND

IONIZING RADIATION

Soon after the discovery of radioactivity, researchers including the pioneers had to deal with the effects of radiation on living tissues. Pierre Curie, for example, kept a vial of Radium on his pocket, only to find later that his skin is severely damage. Marie Curie, died of a malignant blood disease because of her exposure to radiation. Accident had also led to the loss of over 300 lives due to the exposure to high doses of radiation.

The reason why ionizing radiation is harmful to living organisims is that it causes ionization within the cells. From your chemistry reactiveand can cause a series of undersirable reactions such us damaging the cells. It may also lead to cell death.

1 Sv

1µSv

1mSv

Total dose of radiation therapy (30-70Gy)

Daily dose of standard radiation therapy(2 Gy)

Natural radiation/year (2mSv)

Lethal dose of whole body exposure (~4Gy)

Daily dose of radiation from diet (1µSv)

Upper gastro-intestinal exam (2mSv)

DOSE LEVEL

ORGAN SENSITIVI

TY

Tissue/ organ sensitivity

Gonads (ovary and testes) 0.25

Breast 0.15

Red Bonemarrow 0.12

Lungs 0.12

Thyroid Gland 0.03

Bone Surface 0.03

All other organs 0.30

Sensitivity of Organs to Radiation

A100 SvB

10-50Sv

C3-5 Sv

A Death by damage to the central nervous system within hours or day.

A Death by damage to the digestive system in 1-2 weeks.

Time (weeks)

1 2 3 4 5 6

ACUTE VS.

LONG-TERM

EFFECTS

The effects of radiation that appear months, or even years after exposure to radiation are called DELAYED or LONG-TERM EFFECTS. Leukemia and the formation of cancerous tumors are two of the most important delayed effects of radiation.

0 10 20 30

Leukemia

All other cancers

The relationship between the dose received and its effect on humans is not actually a simple one. For purposes of protecting humans from the harmful effects of radiation, the International Atomic Energy Ageny (IAEA) came up with the graph show.

10-3 10-2 10-1 1 10

10

-5

10

-4

10

-3

10

-2

10

-1

1

The International Commission for Radiological Protection (ICRP) currently recommends that in addition to the dose received from natural background radiation, the general public like us should have a whole body dose limit of 1 mSv/year. Workers in the radiation industry working in nuclear medicine research institute and dose at 50 mSv/year. The ICRP, however, suggested that all exposures to radiation be kept “as long as reasonably achievable”- or ALARA limit.

THANK YOU FOR LISTENING,,, HOPE YOU

LEARNED A LOT ^_^

PREPARED BY GROUP 10 ♥

EARL ANGELICA K. LESACA

JESSA GUEVARRA

MARYROSE MALACAMAN

WENDEL TIBOR

BERNARD ANTONIO