Give the definitions of the following notions.

1. closed energy cycles
2. radioactive-energy-release
3. conservation of energy
4. natural precursor
5. natural radioactivity
6. threshold gamma-ray energy
7. excess mass
8. mass spectroscopy

Translate the sentences below. Mind the functions of the Infinitive and the Infinitive Constructions.

 

1. To anticipate is to look forward, to see what must be done and to do it in advance.

2. To allow for all possible types of interactions and reflections, however, would be a formidable task in this event.

3. To eliminate the inconsistency of measuring the force on a unit area by a unit of length, the air pressure is now measured for meteorological purposes in terms of a unit of 1.000 dynes cm- called a millibar (mb).

4. According to the law of conservation of energy, any energy acquired by an atom is to be eventually given off.

5. Each atom is to be governed by the mean potential due to all the other atoms at rest in their mean positions.

6. Your prime task has been to record the directions to be executed exceedingly accurately.

7. The problem is to confine hot plasma long enough for a fusion reaction to take place.

8. A traditional approach to the problem is to eliminate bulky calculations. It may require a lot of auxiliary operations.

9. An amplifier to boost the signal would be required before the signal is fed to the input.

10. The discovery of uranium fission is one to exert greater influence on the events to come than any other discovery in the past century.

11. There are a number of advantages to be gained from using a liquid as the active medium in a laser rather than a solid or a gas.

12. Apart from this, eigenvalues to be obtained for excited electronic states in most cases agree reasonably with experimental binding energy.

13. These electrons are always freely available to conduction. A partially filled band is created whenever the orbitals that combine to form the band are not fully occupied.

14. In the modern conception, the strong nuclear force binds quarks together to form elementary particles such as protons and neutrons.

15. Unfortunately the period of visibility of a comet is generally too short to allow any extensive measurements.

16. The combination of three quarks is sufficient to account for the hadrons that have been observed or predicted by the rigorous theory.

17. When two identical atoms are brought together closely enough for their orbits to overlap, each energy level is split to create two new levels, below and above the original level.

18. Positrons typically live a few hundred picoseconds, roughly the time it takes for a light to travel one centimeter.

19. For the effect to be readily observable a great deal of energy must be concentrated in a narrow band of wavelengths, the narrower the better.

20. It is possible for excitation to take place in successive steps by the absorption of two or more quanta of energy.

Work in 2 groups. Read the text again and extract the information required for the chosen theme (1-2) and start discussion.

Energy release in radioactive transitions

1. Calculation and measurement of energy

 

LISTENING

You are going to listen to the staff report “Uranium Report: Plenty More Where That Came From“. Mind the proper names.

IAEA

Organization for Economic Co-operation and Development Nuclear Energy Agency (OECD/NEA)

2. Listen to the staff report “Uranium Report: Plenty More Where That Came From“. Note only the essential details of what you hear:

1. A report released today …
2. Growing demand and higher prices …
3. Uranium 2007: Resources, Production and Demand …
4. Red Book …
5. The uranium market …
6. The demand picture is increasingly complex …
7. In contrast to some other energy resources …
8. Since 1965, the IAEA and the Organization for Economic Co-operation and Development Nuclear Energy Agency (OECD/NEA) …

3. Listen to the staff report again and complete the gaps in sentences below with the correct word or phrase you hear:

1. Amid heightened international interest in nuclear energy, countries are _______________ to a finite resource that helps to make nuclear power possible: uranium.
2. … and led to larger identified _______________ over the past two years.
3. … it tracks present ______________ and assesses market dynamics to 2030 and beyond
4. Over _______________ was spent globally on exploration in 2006.
5. Yet the report notes that new builds along with plant life extensions should increase global installed ______________ in the coming decades, thereby increasing demand for uranium.
6. Currently uranium is mined in 20 countries, with Iran being _____________.
7. Canada and Australia currently account for _____ of global uranium production, and other top uranium producers are Kazakhstan (_____), Niger (_____), Russian Federation (_____), Namibia (_____), Uzbekistan (_____), and the United States (_____).
8. The report’s contents are made possible through _______________ obtained by questionnaires sent to relevant IAEA and OECD/NEA member countries, which number 40 in total.

Work in pairs or groups. Discuss the topic mentioned in the staff report “Uranium Report: Plenty More Where That Came From “.

PRESENTATION

Make up a presentation “RADIOACTIVITY”

(See appendix 4)

SECTION 7

NEUTRON INTERACTIONS

LEAD-IN

 

Comment the statement below.

Neutrons can cause many different types of interactions. The neutron may simply scatter off the nucleus in two different ways, or it may actually be absorbed into the nucleus. If a neutron is absorbed into the nucleus, it may result in the emission of a gamma ray or a subatomic particle, or it may cause the nucleus to fission.

 

READING

TEXT 1

Before reading the text, decide in small groups (2-3 students) whether these statements are true or false using your knowledge of the subject. Then read the text and check your guesses.

1. Light scattering explains colour of some objects, usually shades of red.

2. The main factor influencing the process of scattering is the ratio of the particle diameter to the wavelength of the radiation.

3. The problem of electromagnetic scattering for large diameters is still being solved and attracts much attention.

4. When the ratio of particle diameter to wavelength is more than about 10, the term scattering is not usually applied.

5. A laser beam is a model for studying coherent backscattering.

The following sentences have been removed from the text. Choose from the sentences A-J the one which fits each gap (1 – 9). There is one extra sentence which you don’t need to use.

 

A In the Mie regime, the shape of the scattering center becomes much more significant and the theory only applies well to spheres and, with some modification, spheroids and ellipsoids.

B The first is fairly obvious, that it is difficult to measure the direct backscatter without blocking the beam, but there are methods for overcoming this problem.

C In this size regime, the exact shape of the scattering center is usually not very significant and can often be treated as a sphere of equivalent volume.

D Major forms of elastic light scattering (involving negligible energy transfer) are Rayleigh scattering and Mie scattering.

E When one looks at the sky during the day, rather than seeing the black of space, one sees light from Rayleigh scattering off the air.

F For relatively large and complex structures, these models usually require substantial execution times on a computer.

G The absence of surface scattering leads to a shiny or glossy appearance.

H Weak localization of light can be detected since it is manifested as an enhancement of light intensity in the backscattering direction.

I This phenomenon, is the result of many sinusoidal two-wave interference patterns which add up.

J This shift involves a slight change in energy.

 

Electromagnetic Scattering

Electromagnetic (EM) waves are one of the best known and most commonly encountered forms of radiation that undergo scattering. Scattering of light and radio waves (especially in radar) is particularly important. Several different aspects of electromagnetic scattering are distinct enough to have conventional names. 1)_____. Inelastic EM scattering effects include Brillouin scattering, Raman scattering, inelastic X-ray scattering and Compton scattering.

Light scattering is one of the two major physical processes that contribute to the visible appearance of most objects, the other being absorption. Surfaces described as white owe their appearance almost completely to the scattering of light by the surface of the object. 2) ______. Light scattering can also give color to some objects, usually shades of blue (as with the sky, the human iris, and the feathers of some birds), but resonant light scattering in nanoparticles can produce different highly saturated and vibrant hues, especially when surface plasmon resonance is involved.

Rayleigh scattering is a process in which electromagnetic radiation (including light) is scattered by a small spherical volume of variant refractive index, such as a particle, bubble, droplet, or even a density fluctuation. This effect was first modeled successfully by Lord Rayleigh, from whom it gets its name. In order for Rayleigh's model to apply, the sphere must be much smaller in diameter than the wavelength (λ) of the scattered wave; typically the upper limit is taken to be about 1/10 the wavelength. 3) ___. The inherent scattering that radiation undergoes passing through a pure gas is due to microscopic density fluctuations as the gas molecules move around, which are normally small enough in scale for Rayleigh's model to apply. This scattering mechanism is the primary cause of the blue color of the Earth's sky on a clear day, as the shorter blue wavelengths of sunlight passing overhead are more strongly scattered than the longer red wavelengths according to Rayleigh's famous 1/λ ⁴ relation. Along with absorption, such scattering is a major cause of the attenuation of radiation by the atmosphere. The degree of scattering varies as a function of the ratio of the particle diameter to the wavelength of the radiation, along with many other factors including polarization, angle, and coherence.

For larger diameters, the problem of electromagnetic scattering by spheres was first solved by Gustav Mie, and scattering by spheres larger than the Rayleigh range is therefore usually known as Mie scattering. 4) ____. Closed-form solutions for scattering by certain other simple shapes exist, but no general closed-form solution is known for arbitrary shapes.

Both Mie and Rayleigh scattering are considered elastic scattering processes, in which the energy (and thus wavelength and frequency) of the light is not substantially changed. However, electromagnetic radiation scattered by moving scattering centers does undergo a Doppler shift, which can be detected and used to measure the velocity of the scattering center/s in forms of techniques such as LIDAR and radar. 5) _____.

At values of the ratio of particle diameter to wavelength more than about 10, the laws of geometric optics are mostly sufficient to describe the interaction of light with the particle, and at this point the interaction is not usually described as scattering.

For modeling of scattering in cases where the Rayleigh and Mie models do not apply such as irregularly shaped particles, there are many numerical methods that can be used. The most common are finite-element methods which solve Maxwell's equations to find the distribution of the scattered electromagnetic field. Sophisticated software packages exist which allow the user to specify the refractive index or indices of the scattering feature in space, creating a 2- or sometimes 3-dimensional model of the structure. 6) __.

Another special type of EM scattering is coherent backscattering. This is a relatively obscure phenomenon that occurs when coherent radiation (such as a laser beam) propagates through a medium which has a large number of scattering centers, so that the waves are scattered many times while traveling through it. A thick cloud is a typical example of this sort of multiple-scattering medium. The effect produces a very large peak in the scattering intensity in the direction from which the wave travels—effectively, the light scatters preferentially back the way it came. For incoherent radiation, the scattering typically reaches a local maximum in the backward direction, but the coherent backscatter peak is two times higher than the level would have been if the light were incoherent. It is very difficult to detect and measure for two reasons. 7) __. The second is that the peak is usually extremely sharp around the backward direction, so that a very high level of angular resolution is needed for the detector to see the peak without averaging its intensity out over the surrounding angles where the intensity can undergo large dips. At angles other than the backscatter direction, the light intensity is subject to numerous essentially random fluctuations called speckles.

This is one of the most robust interference phenomena that survives multiple scattering, and it is regarded as an aspect of a quantum mechanical phenomenon known as weak localization. In weak localization, interference of the direct and reverse paths leads to a net reduction of light transport in the forward direction. This phenomenon is typical of any coherent wave which is multiple scattered. It is typically discussed for light waves, for which it is similar to the weak localization phenomenon for electrons in disordered (semi)conductors and often seen as the precursor to Anderson (or strong) localization of light. 8) ___. This substantial enhancement is called the cone of coherent backscattering.

Coherent backscattering has its origin in the interference between direct and reverse paths in the backscattering direction. When a multiply scattering medium is illuminated by a laser beam, the scattered intensity results from the interference between the amplitudes associated with the various scattering paths; for a disordered medium, the interference terms are washed out when averaged over many sample configurations, except in a narrow angular range around exact backscattering where the average intensity is enhanced. 9) ___. The cone is the Fourier transform of the spatial distribution of the intensity of the scattered light on the sample surface, when the latter is illuminated by a point-like source. The enhanced backscattering relies on the constructive interference between reverse paths. One can make an analogy with a Young's interference experiment, where two diffracting slits would be positioned in place of the "input" and "output" scatterers.