acads (08-006) covered keywords radioactivity, radioactive decay, half-life, nuclide, alpha, beta,...

ACADs (08-006) Covered

Keywords

Radioactivity, radioactive decay, half-life, nuclide, alpha, beta, positron.

Description

Supporting Material

1.1.4.2 3.3.1.1 3.3.1.7 4.9.1 4.9.7

OBJECTIVES

• Define the following terms associated with radioactive decay:– radioactivity– radiation– radioactive decay– half-life

• State the difference between radioactivity and radiation.

FEN-BET-I764 Rev. 0 2

OBJECTIVES

• Using the Chart of the Nuclides and given a stable nuclide, determine the following:– Element Name– Atomic Number (A)– Atomic Mass (Z)– Isotopic Mass– Atom Percent Abundance (%)


OBJECTIVES

• Using the Chart of the Nuclides and given a man-made radioactive nuclide, determine the following:– Element Name– Atomic Number (A)– Atomic Mass (Z)– Half-Life


OBJECTIVES

• Describe the following types of decay in terms of the requirements for and mode of occurrence, the resulting products, and emissions:– Alpha– Beta– Positron– Electron capture


PRESENTATION

RADIOACTIVE DECAY TERMS

• Radioactivity is defined as “that ability of an unstable nucleus to spontaneously emit particles and/or energy to achieve a more stable state.”

• Radiation is defined as “energy or particles propagated through space.”


RADIOACTIVE DECAY TERMS• Radioactive decay is defined as “that process

in which an unstable nucleus spontaneously emits particles and/or energy to achieve a more stable state.”

• Half Life (t1/2), is defined as “the time required for one-half of the nuclei of a given radioactive material to undergo radioactive decay.” Half Life is unique to each nuclide and is expressed in seconds, minutes, hours, days, or years.


RADIOACTIVITY v.s. RADIATION

RadioactivityThe spontaneous

nuclear transformation that usually results in

the formation of a different nuclide.

RadiationEnergy or particles propagated through

space.


Be sure you know the difference between these two. They are not the same!!

RADIOACTIVE DECAY• As mass numbers of nuclei become larger,

the neutron to proton ratio becomes larger for the stable nuclei.

• Non-stable nuclei may have an excess or deficiency of neutrons and undergo various decay processes such as beta (- or +), alpha (), neutron (n), or proton (p) decay.

• The result of these decay processes provides a more stable configuration.


RADIOACTIVE DECAY

CHART OF THE NUCLIDES

Chart of the Nuclides


The Vertical Column of Numbers liststhe Atomic Number or “Z Number”

for each associated row. It describeshow many protons are in that row

Z



The Horizontal Row of Numbers liststhe “N Number” for each associated

column. It describes how manyneutrons are in that column.

N



Each box in the chart contains informationabout that particular nuclide.

Let’s look at some examples.



These are the heavily borderedSquares at the end of each row.

It contains the chemical symboland properties of the element

as found in nature.These properties include:

H

1.00794

Hydrogen

- Symbol

- Atomic Weight (Carbon -12 Scale)

- Element Name

- Thermal Neutron AbsorptionCross-Section in Barns Followed by Resonance Integral, in Barns

a .333,.150

ChemicalElement

Atomic weight

Thermal neutron absorption cross-section

Stable Nuclides


Chemical symbol with atomic mass number.

- Symbol, Mass Number

Atom Percent Abundance -Thermal Neutron Capture Cross-Sections inBarns Leading to (Isomeric + Ground State),Followed by Resonance Integrals Leading to (Isomeric + Ground State).

Isotopic Mass (Carbon - 12 Scale) -

Isotopic abundance (%)

Thermal neutron absorption cross section

Isotopic mass of neutral atom on C12

scale

A stable nuclide is naturally stable and found in nature.

This box contains the following information:

Long-Lived, Naturally Occurring Radioactive Nuclides


The black rectangle indicates that the

isotopeis radioactive and found in nature.

La 1380.090

1.05e11 a

Symbol, Mass Number -

- Half-Life

Thermal Neutron Capture Cross-Section, Followed by Resonance Integral.

, -.25 1435.8, 788.7 ~57,4E2

Naturally Occurring or Otherwise Available but Radioactive

E 1.04 137.90711 - Beta Disintegration Energy Followed byIsotopic Mass

5+

- Atom Percent Abundance

Modes of Decay in Order of Prominence withEnergy of Radiation in MeV for Alpha andBeta; keV for Gammas.

Squares with both black rectangles and gray represent naturally occurring isotopes with a very long half life.

Long-Lived, Naturally Occurring Radioactive Nuclides (more)



Isotopic abundance (%)

Half-Life

Isotopic mass of neutral atom on C12

scale

La 1380.090

1.05e11 a

Symbol, Mass Number -

- Half-Life

Thermal Neutron Capture Cross-Section, Followed by Resonance Integral.

, -.25 1435.8, 788.7 ~57,4E2

Naturally Occuring or Otherwise Available but Radioactive

E 1.04 137.90711 - Beta Disintegration Energy Followed byIsotopic Mass

5+ - Spin and Parity

- Atom Percent Abundance

Modes of Decay in Order of Prominence withEnergy of Radiation in MeV for Alpha andBeta; keV for Gammas.

Decay modes and decay

energies in MeV for ,; keV for .

Man-Made Radionuclides



Half-Life

Decay modes in MeV for ,; keV for .

Emax of Beta Energy

S38

2.84 h

- Symbol, Mass Number

- Half-Life

- Beta Disintegration Energy in MeV.

- .99, ... 1941.9 ...

Artificially Radioactive

E 2.94

Modes of Decay with Energy of Radiation inMeV for Alpha and Beta; keV for Gammas.

LINE OF STABILITY


Note that there is a line of stable atoms (gray boxes) that run diagonally through the entire Chart of the Nuclides.This is known as the “Line of Stability”. It is where all radioactive isotopes will eventually come to rest after one or more decay events.

ACADs (08-006) Covered

Keywords

Description

Supporting Material

3.3.1.7

4.91.

TYPES OF RADIOACTIVE DECAY


• There are many types of Radioactive Decay. We will discuss the following:

–Alpha particle emission–Beta emission (both - and +);–Gamma emission–Electron capture

ALPHA EMISSION DECAY

• A large, loosely packed nuclei will decay by alpha emission. An alpha particle () is released from its nucleus.

• An alpha particle () is a Helium (He) nucleus (a Helium atom minus its two electrons).


ALPHA DECAY


In Alpha decay 2 neutrons and 2 protons are emitted forming an particle.

ALPHA EMISSION DECAY• The Helium nucleus has two (2) protons, and

two (2) neutrons.• When released from the original nucleus, the

new nucleus will have an Atomic Number two less than its original and an Atomic mass of four less than its original.

• Let’s look at a couple of graphic demonstrations of this type of decay on the Chart of the Nuclides.



New Isotope

Old Isotope

ALPHA

DECAY

N -2 N -1 N N +1 N +2

EXAMPLE


Americium 242 emits an and transforms into Neptunium 238

BETA MINUS DECAY

• In a beta minus (-) decay, a nuclei emits a negative charge from the nucleus.

• A - is identical in charge and mass of an electron.

• In - decay, a neutron is converted to a proton, causing the nuclide’s Atomic Number to increase by one (1), but the Atomic Mass to stay the same.


BETA MINUS DECAY


In Beta minus decay a neutron changes to a proton with the emission of a -.

-

BETA MINUS DECAY

• - decay is the primary emission mode of radioactive nuclides that are born below the Line of Stability.

• Let’s look at a couple of graphic demonstrations of this type of decay on the Chart of the Nuclides.



Old Isotope

New Isotope-

DECAY

N -2 N -1 N N +1 N +2

EXAMPLE OF - DECAY


Cesium 137 emits a - and transforms into Barium 137

POSITRON (+) DECAY


In Positron decay, a proton changes to a neutron with the emission of a + .

+

Besides the emission of a +, the Atomic Number (A number) of the nucleus goes down by 1 and the Atomic Mass (Z number) stays the same.

ELECTRON CAPTURE ()


In Electron Capture an electron is captured by the nucleus, changing a proton to a neutron with the emission of a characteristic X-Ray and a +.

+

X-ray

The end results are the same as a + decay discussed previously. The A number goes down by 1 and the Z number stays the same.

EXAMPLE OF + AND DECAY


Lanthanum 136 captures an electron or emits a + and transforms into Barium 137


Old Isotope

N -2 N -1 N N +1 N +2

CAPTURE

DECAY

+

or

ELECTRON

New Isotope

SUMMARY

• Summarize Objectives with students.


acads (08-006) covered keywords radioactivity, radioactive decay, half-life, nuclide, alpha, beta,...

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