RADIOACTIVITY EXPLORATION METHOD PART-II.ppt

7/29/2019 RADIOACTIVITY EXPLORATION METHOD PART-II.ppt

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Radioactivity is the spontaneousemission of energy from unstable

atoms.



Radioactivity refers to the particleswhich are emitted from nuclei as aresult of nuclear instability. Because

the nucleus experiences the intenseconflict between the two strongestforces in nature, it should not besurprising that there are manynuclear isotopes which are unstable

and emit some kind of radiation. Themost common types of radiation arecalled alpha, beta, and gammaradiation, but there are several othervarieties of radioactive decay.



Historically, the products of radioactivity were called alpha,

beta, and gamma when it wasfound that they could be analyzedinto three distinct species byeither a magnetic field or an

electric field.





Though the most massive andmost energetic of radioactiveemissions, the alpha particle is the

shortest in range because of itsstrong interaction with matter.

The electromagnetic gamma ray isextremely penetrating, even

penetrating considerablethicknesses of concrete.

The electron of beta radioactivity

strongly interacts with matter and





Radioactive decay is the processby which an atomic nucleus of an

unstable atom loses energy byemitting ionizing particles(ionizing radiation).

The emission is spontaneous, inthat the atom decays without anyinteraction with another particle

from outside the atom (i.e.,



Usually, radioactive decay happensdue to a process confined to the

nucleus of the unstable atom, but,on occasion (as with the differentprocesses of electron capture andinternal conversion), an inner

electron of the radioactive atom isalso necessary to the process.



The daughter nuclide of a decayevent may also be unstable

(radioactive). In this case, it willalso decay, producing radiation.The resulting second daughternuclide may also be radioactive.

This can lead to a sequence of several decay events. Eventually, astable nuclide is produced. This is

called a decay chain.



An example is the natural decay chain Uranium-238 which is as follows:

decays, through alpha-emission, with a half-life of 4.5 billion years tothorium-234

which decays, through beta-emission, with a half-life of 24 days toprotactinium-234

which decays, through beta-emission, with a half-life of 1.2 minutes touranium-234

which decays, through alpha-emission, with a half-life of 240 thousandyears to thorium-230

which decays, through alpha-emission, with a half-life of 77 thousandyears to radium-226

which decays, through alpha-emission, with a half-life of 1.6 thousand

years to radon-222 which decays, through alpha-emission, with a half-life of 3.8 days to

polonium-218

which decays, through alpha-emission, with a half-life of 3.1 minutes tolead-214

which decays, through beta-emission, with a half-life of 27 minutes tobimuth-214

which decays, through beta-emission, with a half-life of 20 minutes topolonium-214



The decay rate, or activity, of a radioactivesubstance are characterized by:

half life— symbol t 1/2 — the time taken for the

activity of a given amount of a radioactivesubstance to decay to half of its initial value.

mean lifetime— symbol τ — the average lifetime of aradioactive particle.

decay constant— symbol λ — the inverse of the

mean lifetime.Although these are constants, they are associatedwith statistically random behavior of populations of atoms. In consequence predictions using theseconstants are less accurate for small number of

atoms.



Our world is radioactive and has been since it was created. Over60 radionuclides (radioactive elements) can be found in nature,and they can be placed in three general categories:

1. Primordial - from before the creation of the Earth2. Cosmogenic - formed as a result of cosmic ray interactions3. Human produced - enhanced or formed due to human actions

(minor amounts compared to natural)

Radionuclides are found naturally in air, water and soil. They areeven found in us, being that we are products of ourenvironment. Every day, we ingest and inhale radionuclides inour air and food and the water. Natural radioactivity is commonin the rocks and soil that makes up our planet, in water andoceans, and in our building materials and homes. There is

nowhere on Earth that you can not find Natural Radioactivity. Radioactive elements are often called radioactive isotopes or

radionuclides or just nuclides. There are over 1,500 differentradioactive nuclides. Often, radionuclides are symbolized basedon the element and on the atomic weight, as in the case of radioactive hydrogen or tritium with an atomic weight of 3 isshown as H-3 or 3H. As another example, Uranium with theatomic weight of 235 would be shortened to U-235 or 235U.



The Becquerel (symbol Bq)(pronounced: 'be-k -rel) is the SI-ə

derived unit of radioactivity. One Bqis defined as the activity of aquantity of radioactive material inwhich one nucleus decays per

second. The Bq unit is thereforeequivalent to s−1. The Becquerel isnamed for Henri Becquerel, whoshared a Nobel Prize with Pierre and

Madame Curie for their work in



When measuring radioactivity of asample with a detector, a unit of "counts per second" (cps) or “countsper minute" (cpm) is often used.These units can be converted to theabsolute activity of the sample in Bq

if one applies a number of significantconversions, e.g., for the radiationbackground, for the detectorefficiency, for the counting geometry,

for self-absorption of the radiation in



The curie (Ci) is an older, non-SI unitof radioactivity equal to the activityof 1 gram of radium-226.

The conversion factors are: 1 Ci = 3.7×1010 Bq 1 Ci = 37 GBq

1 Ci = 37,000 Bqμ 1 Bq = 2.70×10−11 Ci 1 Bq = 2.70×10−5 Ciμ

1 GBq = 0.0270 Ci



Dosimeters measure anindividual's or an object’sexposure to something in the

environment — particularly to ahazard inflicting cumulativeimpact over long periods of time,or over a lifetime.

The radiation dosimeter, measuresexposure to ionizing radiation, but

other dosimeters also exist, such







Uranium Mining

Source of Energy

Nuclear Submarine FuelHeart Pacemaker Battery

Thermo Electric Battery

Medical Usage

Nuclear Weapons















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RADIOACTIVITY EXPLORATION METHOD PART-II.ppt

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