About RI
1. Definition of RI
An RI is an artificial RadioIsotope made from a nuclear reaction.
In the isotope, the atomic nucleus gives radiation rays automatically, and brakes down into the atomic nucleus of other kinds.
And it is unrelated to the outside conditions like pressure, temperature, chemical treatment, and so on.
2. Practical use of RI
2.1 Radio therapy
I'll show as follows, the radioisotope used to earlier detection of disease and treatment for cancer, etc.
2.1.1 Research
In vivo test:
Administers the medicine including the radioisotope to the human body, and we inspect for diagnosis with the help of the radiation released from it.
This inspection tends to do the measurement of the outside the body by measuring instrument placed near the surface of the body.
But there is a case that measure the sample extracted from human body like blood, urine, and so on.
We inject the physiological saline including technetium-99m made from beta decay of molybdenum-99 into blood vessel, and measure gamma-ray released for outside of human body, then we can inspect accurately about comings and goings of the blood to the heart and a flow of the blood of the whole body.
The radioisotope used by such an inspection has a short half-life said 3 days from six hours.
So the influence to give the human body is extremely small.
Therefore it may be said that it is a safe laboratory method if we do not inspect it in succession.
In late years, cancer checkup by PET(positron emission tomography) came to attract attention.
The positron released from the radioisotope which does positron decay, it combine near electron and become extinct.
Then it release two extinction radiation rays in the 180 degrees direction.
The rays have energy of 0.511 mega-electron-volt.
In such radioisotopes, there are carbon-11(half-life:20.39 minutes), nitrogen-13(half-life:9.965 minutes), oxygen-15(half-life:2.037 minutes), fluorine-18(half-life:109.8 minutes), and so on.
We give medication compound that mixes these isotopes, then We understood accurately position of isotopes that released positron by detect twin extinction radiation rays by many γ-ray detectors arranged around a patient.
With this, cancer compares it with a normal cell, and it has a property of taking in more glucose in a cell.
Using this property, position identification of the cancer is possible.
2.1.2 Therapy
In Japanese adult diseases, the cancer is the highest ill one of the death rates.
Cancer is disease that healthy cell changes and increases suddenly.
This cause is mutation of the K-ras gene.
The things that one cells suddenly multiply and increases numbers, become the things that we should destroy the one by radiation rays surely, and in cancer treatment, the radiation therapy is effective.
There is the gamma knife which attached 201 cobalt-60 for a practical example.
So it is effective to use at affected area like the tumor of the brain.
2.3 The age measurement
In the age measurement, there is a way that using index fossil (a standard fossil) or the heap of stratum, then we decide age of stratum and seek relative age.
But, this way can divide the history of earth depending only by big division.
For this, radiation age can get data as numerical value.
So it can do specifying the times that the creature lived in from a fossil, and deciding what time of the stratum from a rock.
I'll introduce two famous mensuration which used a radioisotope in the following.
2.3.1 Radiocarbon method（Subject:charcoal, grain, shell, and so on）
This dating plays an active part in an archeological field.
Carbon-14 is generated by colliding the high-speed neutron beam that included in cosmic rays and an atomic nucleus of atmospheric nitrogen.
This is combined with oxygen and generates carbon dioxide.
The plant of the natural world absorbs this by photosynthesis.
And the animal absorbs carbon-14 in the same way because an animal eats it.
However, carbon -14 decays without being absorbed when the animals and plants die.
The measurement of the generation is possible by examining the quantity of it.
In addition, according to this method, we can demand the generation between from several hundred years to 26,000 years numerically.
In the recent discovery, there is Hashi-haka Kohun of Sakurai-shi, Nara that used this method of measurement.
This attracted attention that it was near to the death year of Himiko.
2.3.2 Uranium thorium method (Subject:rock, stratum, and so on)
The natural thorium and uranium do disintegration with time and change to lead.
They don't do radioactive rays disintegration more than it after having changed to lead.
Therefore, this can use to age measurement.
The representative mineral which this mensuration is used for is monazite, zircon, a xenotime.
According to this method, we can estimate the age of an old sample of several billions of years.
2.4 The nuclear power plant
In the nuclear power plant, the californium of the radioisotope is used as an early neutron source.
In addition, an object letting the neutron which occurred collide is a radioisotope of the uranium.
And plutonium occurs in the middle of a fission reaction.
For the reasons mentioned above, the nuclear power plant can say the treasure house of the radioisotope.
In addition, as a source of supply of the electricity, it contributes to the society than the age measurement.
When we compare the nuclear power generation with the thermal power generation, In two point-fuel cost and bad influence, the nuclear power generation is overwhelmingly superior than the thermal power generation.
But the place built by influence of the form of geographical features is limited and it may be said that it stops the spread.
However, we cannot rely on only a natural energy to realize a slash of the greenhouse gas that the new government says.
It may be said that the effective practical use of the nuclear power plant is required.
3.1 Comparing with the danger and the effect
The radioisotope has radioactivity.
Therefore it is sure that we are extremely in danger if we take the wrong handling.
However, if it handled by an expert engineer, it has big force that can treat cancer called incurable disease and stop a global warming problem.
The danger of the radioisotope can say it isn't the risk impossible of acceptance when we compare it with the effect judging from the above.
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