Questions and Answers on Radioactive Decay

My responses have not been proof read.

Q
Theory for Stability of Isotope
The study of radioactive decays has led to theories of nuclear stability and structure. According to the text however, half lives of nuclides have become known through observation and measurement (pg.106 Lecture Notes). Does a method or law exist for predicting the half life of any given nuclide?
A
Since there are many factors governing the stability of isotopes, we do not have a single or simple theories to predict the half-life of radioactive isotopes.

Q

How are the (4n+1)series' member, e.g. Np artificial manufactured? What technology is involved?
A
New elements are made via nuclear reactions. Whe shall talk about it when we discuss the application of nuclear reactions.

Q
Neutrino
In the beta decay, what is the significant of the emission of an antineutrino or the absorption of a neutrino?

What is the idea behind the neutrino, how can it have Zero rest mass (and therefore zero mass even when moving) and still cause the Nucleus to recoil from it's emission during radioactive decay?
A
If neutrino is not emitted or absorbed, the principle of conservation of energy is no longer true. The neutrino has zero mass, but energy is released. Release of gamma rays (photons) also causes a recoil.

How do scientists know that neutrinos are a product of beta decay? Have they detected them somehow or is it completely theoretical?
Another same question
It is said that the neutrinos have zero rest mass and zero charge. If this is true, is there a method of detecting neutrinos other than saying the theory of conservation of energy is violated without their existance? I.e. has their existance been proven or just theorized
A
Neutrinos are not product of beta decay, rather particles accompany positron decay. Antineutrinos accompany beta decay. Pauli first postulated the existence of tiny neutral particles and named them neutrinos. Neutrinos are detected some years later. Scientists have to show evidence for their discovery, and evidences are scrutinized by scientists.

Q
Beta decay spectrum and Internal conversion electrons
According to P.137 on Lecture Notes, how do the internal conversion and Auger electrons contribute to the peaks on the Beta Spectrum plot?
A
Internal conversion electrons and Auger electrons are very similar to beta particles, except that they have definite energy. Thus, the beta particle spectrum include these electrons.
See the module on radioactive detection regarding spectrum, internal conversion, and Auger electron.

Q
Structure of neutron
In the section "Properties of Subatomic Particles", it is stated that "even though the neutron has no charge, it has a magnetic moment suggesting a complicated structure". Is the complicated structure explained by it's quark make-up (1u + 2d), or is it unknown at this time?
A
Complicated here means that it's not a point mass. There is a distribution of charges leading to a magnetic moment.

Q
Beta and ejected electrons
Regarding the internal conversion of electrons, it was stated that these ejected electrons were often mistaken for (beta-) particles. What are the differences between (beta-) particles and electrons and how do we use these differences to determine which ones are which?
A
Usually, we cannot differentiate the two types of electrons. However, ejection of electron sometimes is accompanied by the emission of X-rays. Putting all these data together, we understand nature.

Q
Radioactive energy
What significant research has been done to harbour energy from the various types of radioactive decay? Have their been any practical applications of this research?
A
I think you mean harvest radioactive energy. Yes, radioactive energy is used for medical treatment as we shall see in the Application of Nuclear Technology.

Q
Closed shell
Nuclides with closed shells form stable nuclides. Using the four quantum states, n, l, Mj, S. Give the mathematically formula for calculating magic numbers.
A
There is no single and magical rule to evaluate the number of nucleons for a closed shell yet. The closed shell is illdefined except the magic numbers.

Q
Eat radiom
Radium has similar chemical properties as calcium so if ingested, they take the place of calcium in the bone structure; does this mean that we can intake radium instead of calcium or does radium have other unhealthy side-effects on the human body?
A
Radium has no stable isotopes. Eat any amount of radium is dangerous.

Q
The factor A in isomeric transition
On the Isomeric Tranisitions and Half-life chart on page 135 (and in section 4f1 of the lectures), the partial half-life of the magnetic dipole is not a factor of A. Is this A the radioactivity, as defined on page 102, or the mass number, as defined on page 108? What is it about the magnetic dipole that makes it different from all the other radiation types, which are a function of A?
A
Sorry I did not make it clear. A here is the mass number, number of nucleons.

Q
Magnetic moment of electron
Why does the electron have a magnetic moment of slightly more than one Bohr magneton, and why is a difference of 0.001 considered to be "in excellent agreement"?
A
The magnetic moment was measured to be more than 1.0 Bohr magneton. We don't know why. Since the difference is small, we consider the model excellent.

Q
Consecutive decay and growth
In consecutive decay and growth, in case the daughter D has a long half-life compared to that of the parent P, the decrease of radioactivity due to P follows that of a single radioactive nuclei. What does this mean exactly?

How does the presence of a decayed product cause the original to decay faster? ie U decaying to Th. Is it due to the increase in radioactive by products? Wouldn't the faster half life of Th just cause the Th to decay completely and not increase the decay of U?
A
Because the radioactivity of the parent is the same as that of the daughter. Thus, the total radioactivity is about 2 times that of the parent alone. Regarding the maximum time calculation, we don't want to engage too much formula in the course at this point.

The second question sounds confused.

Q

Radioactive detection
In module 4, radioactive decay was discussed and various instruments have been developed to detect radiation both short and long half lives. With short half-lives the radiation levels are quickly reduced to undetectable levels. As the technology develops will we be able to detect levels well below the undetectable levels of today and can those undetectable levels cause health effects over the short/long term exposures?
A
Sensitivity of radioactivity detection have improved, and will continue to improve with technology. We will discuss instrumentation later.
Nuclide with short half-life decays quickly and they post no health concern.

Q
Is it dangerous to talk on cell phone near a microwave that is heating up some food?
A
Microwave and cell phone are using radiation in the microwave region, but the two machines use radiations of different frequencies. If talking on the phone does not detract you from cautions for using the microwave oven, you are fine. If talking lets forget hot food, you may get burned.

A
Radiation hazard
If our bodies are exposed to radiation for an extended period of time, is there a chance that the cells in our bodies will mutate and become radioactive? If the cells do become radioactive, does it emit alpha and beta particles?
A
Exposure to neutron radiation will result in making radioactive isotopes in the body, and beta particles are usually the induced radioactivity.
Exposure to neutron induces nuclear reactions, that affect the nuclei. Atoms in the cells emitt beta particles, not the cells.

Q
Abundances of isotopes
In this module, some abundances of isotopes of elements are discussed. However, how can scientists know these statistics? Do they do any experiments or do they do any research to come up the results?
A
Abundances are determined for each elements. Yes, we spent a lot of effort to determine them by performing experiments. Design and carry out experiment is a form of research.

Q
Smoke detectors
We've heard that common houshold smoke detectors contain a radioactive substance and somehow use this in detecting smoke. How is the detection of smoke related to radioactive decay?
A
Yes, smoke detectors contain a little bit of radioactive material such as americium 241.
The alpha particles emitted by the Am-241 collide with the oxygen and nitrogen in air in the detectorOs ionisation chamber to produce charged particles called ions. A low-level electric voltage applied across the chamber is used to collect these ions, causing a steady small electric current to flow between two electrodes. When smoke enters the space between the electrodes, the alpha radiation is absorbed by smoke particles. This causes the rate of ionisation of the air and therefore the electric current to fall, which sets off an alarm.
The alpha particles from the smoke detector do not themselves pose a health hazard, as they are absorbed in a few centimetres of air or by the structure of the detector.