Ch. 32 - Ionizing Radiation, Nuclear Energy, & Elementary Particles

The current view of how matter is composed of basic units

Molecule → Atom → Nucleus → Neutron (or proton) → Quark

Environmental radiation

Natural and artificial radiation

Natural radiation

Cosmic rays & earth itself.

Artificial radiation

Medical diagnostics and manmade sources.

Ionizing radiation

Consists of photons and/or moving particles that have sufficient energy to knock an electron out of an atom or molecule, thus forming an ion.

Exposure

A measure of the ionizing radiation produced in air by x-rays or γ-rays.

Exposure (in roentgens) =

(1 / 2.58 × 10^-4) q / m

RADs (radiation absorbed dose) =

The unit of absorbed dose.

One rad is = to…

0.01 J of radiant energy absorbed per 1 kg of tissue.

Absorbed dose =

energy absorbed / mass of absorbing material

1 gray = 1Gy = 1 J/kg = 100rad

Relative biological effectiveness (RBE)

Used to compare the damage produced ny different types of radiation.

RBE =

Dose of 200 -keV X-rays that produces a certain biological effect / Dose of radiation that produces the same biological effect

Biologically equivalent dose =

absorbed dose x RBE 1Sv (seivert) = 100rem

REMs (roentgen equivalent man) =

The unit of radiation dosage based on potential damage and accounts for the different health effects of different types of radiation determined by clinical studies.

Lethal dose of radiation

> 500 rems

~50% survival chance

The average person in the US is exposed to ~ _____________ a year.

360 mrems

Nuclear reaction

Said to occur whenever the incident nucleus, particle, or photon causes a change to occur in the target nucleus.

An Induced Nuclear Transmutation Example

An alpha particle strikes an aluminum nucleus. As a result,

an unknown nucleus and a neutron are produced.

⁴₂He + ²⁷₁₃Al → ^A_ZX +¹₀n

³⁰₁₅P

Nuclear fission

The colloquial ‘splitting of atoms’

Neutrons and massive energy are released

Applications of weaponry and energy production

Nuclear fission is the process of…

Splitting atoms of heavy elements into two or more smaller atoms.

The splitting of the atom during fission produces…

A tremendous amount of energy in the form of heat and light.

Each fissioning of an atom by one neutron can produce…

From 8-27 additional neutrons, all available for furthering reactions.

Fission chain reaction

Neutrons from one reaction start the next reaction.

Critical mass

The point at which the chain reaction becomes self-sustaining.

The amount of fissionable material’s critical mass depends on:

The shape of the material, its composition and density, and the level of purity.

Nuclear fusion

Two nuclei of very low mass can combine to generate energy.

When atoms are fused, atoms of ligher masses produce…

More energy than those of heavier masses.

Fusion vs Fission

Both release large amounts of energy.

Fission is more effective as of today.

Generating fusion - how to confine the plasma?

Gravitational confinement

Magnetic confinement

Internal confinement

All stars have…

Fusion cores.

The fusion reactor

Uses massive magnetic field to control the heated plasma produced by powerful lasers.

Biological effects of Ionizing Radiation Example

Biologically equivalent doses are specified in units called ________.

a) rads

b) grays

c) rems

d) J/kg

e) roentgens

c) rems

Induced nuclear reactions Example

Determine the unknown nuclear species ^A_ZX in the following nuclear reaction:

^A_ZX + ¹⁴₇N → ¹⁴₆C + ¹₁H

a) ²₁H

b) ¹₀n

c) γ ray

d) ⁴₂He

b) ¹₀n

Nuclear Fission Example

The fission of ²³⁵₉₂U can occur via many different reactions. In general, they can be written as follows:

¹₀n + ²³⁵₉₂U → ^Ax_ZxX + ^Ay_ZyY + n¹₀n

where X and Y refer to the identities of the fission fragments and n is the number of neutrons produced. Which one or more of the following statements are true?

A) The compound nucleus that is formed to initiate the fission process is the

same, no matter what the X and Y refer to.

B) The greater the number n of neutrons produced by the reaction, the smaller

is the sum of the nucleon numbers Ax and Ay.

C) The sum of the atomic numbers Zx and Zy is the same, no matter what the X

and Y refer to.

a) A

b) A and B

c) A and C

d) B and C

e) A, B, and C

e) A, B, and C

Nuclear Fusion Example

In each of the following three nuclear fusion reactions, the masses of the nuclei are given beneath each nucleus. Rank the energy produced by each reaction in descending order (greatest first).

a) I, II, III

b) I, III, II

c) II, III, I

d) II, I, III

e) III, II, I

c) II, III, I