physics

Post Irradiation Examination

Post Irradiation Examination is a physics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Post Irradiation Examination rather than just read about it. In short: Post Irradiation Examination (PIE) is the study of used nuclear materials such as nuclear fuel. It has several purposes.

Key takeaways

Post Irradiation Examination belongs to physics; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Post Irradiation Examination to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Post Irradiation Examination from memory before moving on to harder problems.

Reference excerpt

Post Irradiation Examination (PIE) is the study of used nuclear materials such as nuclear fuel. It has several purposes. It is known that by examination of used fuel that the failure modes which occur during normal use (and the manner in which the fuel will behave during an accident) can be studied. In addition information is gained which enables the users of fuel to assure themselves of its quality and it also assists in the development of new fuels. After major accidents the core (or what is left of it) is normally subject to PIE in order to find out what happened. One site where PIE is done is the ITU which is the EU centre for the study of highly radioactive materials. Materials in a high radiation environment (such as a reactor) can undergo unique behaviors such as swelling and non-thermal creep. If there are nuclear reactions within the material (such as what happens in the fuel), the stoichiometry will also change slowly over time. These behaviors can lead to new material properties, cracking, and fission gas release:

Fission gas release As the fuel is degraded or heated the more volatile fission products which are trapped within the uranium dioxide may become free.

Fuel cracking As the fuel expands on heating, the core of the pellet expands more than the rim which may lead to cracking. Because of the thermal stress thus formed the fuel cracks, the cracks tend to go from the centre to the edge in a star shaped pattern. In order to better understand and control these changes in materials, these behaviors are studied.[1][2] [3] [4]. Due to the intensely radioactive nature of the used fuel this is done in a hot cell. A combination of nondestructive and destructive methods of PIE are common. In addition to the effects of radiation and the fission products on materials, scientists also need to consider the temperature of materials in a reactor, and in particular, the fuel. Too high fuel temperatures can compromise the fuel, and therefore it is important to control the temperature in order to control the fission chain reaction. The temperature of the fuel varies as a function of the distance from the centre to the rim. At distance x from the centre the temperature (Tx) is described by the equation where ρ is the power density (W m−3) and Kf is the thermal conductivity.

Tx = TRim + ρ (rpellet2 - x2) (4 Kf)−1 To explain this for a series of fuel pellets being used with a rim temperature of 200 °C (typical for a BWR) with different diameters and power densities of 250 Wm−3 have been modeled using the above equation. Note that these fuel pellets are rather large; it is normal to use oxide pellets which are about 10 mm in diameter.

Further reading Radiochemistry and Nuclear Chemistry, G. Choppin, J-O Liljenzin and J. Rydberg, 3rd Ed, 2002, Butterworth-Heinemann, ISBN 0-7506-7463-6

References

External links IAEA (International Atomic Energy Agency) - Post Irradiation Examination Facilities Database

Illustrations

Temperature profile for a 26 mm diameter fuel pellet with a power density of 250 W per cubic meter

Temperature profile for a 32 mm diameter fuel pellet with a power density of 250 W per cubic meter

Temperature profile for a 20 mm diameter fuel pellet with a power density of 500 W per cubic meter. Because the melting point of uranium dioxide is about 3300 K, it is clear that uranium oxide fuel is overheating at the center.

Temperature profile for a 20 mm diameter fuel pellet with a power density of 1000 W per cubic meter. The fuels other than uranium dioxide are not compromised.

Worked examples

Example 1 — a first encounter with Post Irradiation Examination

Start with the simplest possible case. Write down what Post Irradiation Examination claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Post Irradiation Examination before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Post Irradiation Examination ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Post Irradiation Examination

In research: Post Irradiation Examination appears in physics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Post Irradiation Examination in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Post Irradiation Examination is common in secondary-school and first-year university syllabi. It links to neighbouring topics Actinides, Nuclear chemistry, Nuclear materials, so understanding it makes those chapters shorter.
In everyday life: Look for Post Irradiation Examination outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Post Irradiation Examination in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Post Irradiation Examination means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Post Irradiation Examination out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Post Irradiation Examination in simple terms?

Post Irradiation Examination (PIE) is the study of used nuclear materials such as nuclear fuel. It has several purposes.

Why does Post Irradiation Examination matter?

Because it connects several physics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Post Irradiation Examination?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Post Irradiation Examination.