Basic chemistry

Nuclear reactor physics

Nuclear plants

No specific suggestion for courses to be attended in parallel.

No specific suggestion.

Delivery: face to face

Attendance: Advised

Learning activities:

• attending lectures
• participation in seminar
• preparation of oral/written report

Teaching methods:

• Lectures
• Seminar
• project work

First section: Fuel cycle and materials selection criteria

Fundamentals of nuclear reactor systems. Types of reactors: classification in term of neutron energy, reactor purpose, type of coolant.

A simple reactor design. Main characteristics of reactors of Gen I, Gen II, Gen III, and Gen IV reactors.

The nuclear fuel cycle. Finding and mining Uranium: Uranium ores and uranium minerals (reduced species and oxidized species). Basic chemistry concepts on oxidation state of the elements into compounds.

Acid leaching and basic leaching. In-situ leaching. Treatment of uranium solutions; the yellow cake. Refining uranium; liquid-liquid extraction using TBP.

Basic concepts related to a general isotope enrichment process: relative isotopic abundance, separation factor, separation gain, enrichment factor. Enrichment of UF6 by diffusion. Typical diffuser scheme. Diffusion membrane characteristics. Pros and cons of a diffusion plant. Numerical example for an ideal diffusion separation cascade with no-tails; calculation of the minimum number of separation stages in an ideal diffusion cascade.

Basic principles of separation in a force field. Separation in a gravity field. Enrichment of UF6 by centrifugation. The Zippe centrifuge. Pros and cons of a centrifugation plant. Numerical example for an ideal centrifugation separation cascade with no tails; calculation of the minimum number of separation stages in an ideal centrifugation cascade.

Laser isotope separation techniques. Isotope separation based on hyperfine structure. Atomic separation: the AVLSI technique. Molecular separation: the MLIS technique. The aerodynamic separation: the jet nozzle technique. Comparison between different separation techniques.

Fabrication of fuel elements: production of UO2 by humid or dry path.
The back-end operation in the fuel cycle: reprocessing and recycling. The PUREX process: fuel decladding, shearing, dissolution, separation of U and Pu from waste, separation of Pu from U, final product conversion.

General criteria for material selection. Requirements and materials for fuel cladding, moderator and reflectors, coolants, control materials, shielding materials. Example: fuel cladding materials for LWRs; properties of Be, Mg, Al, Zr; Zr based alloys – Zircaloy-2 and Zircaloy-4.

Extraction of Zr from ore; the modified Kroll process. Zr-Hf separation processes: principles and characteristics of the MIBK and TBP processes.

Second section: materials radiation damage

Structure and properties of metallic materials. Elementary cells, Miller and Bravais notation.

Point defects. Linear defects. Dislocations. Classification of crystals and dependence between mechanical properties and crystal structure of materials.

The role of imperfections, state of stress, temperature and strain rate in mechanical properties.

Interaction of neutrons with matter: capture and scattering. Collision cross-sections, neutron flux and mean free path. Radiation damage: knock-on damage, transmutation, bubble formation, swelling.

Collision theory: displacement threshold, cut-off energy. Damage geometry: displacement spike, thermal spike.

Effects of radiation on physical and mechanical properties Enhanced diffusivity, creep, phase stability, radiation hardening, embrittlement and corrosion.

Radiation growth in uranium and graphite, thermal ratcheting of reactor fuel assemblies. Annealing processes. Wigner energy release in graphite.

Radiation-resistant construction steels Overview of structural-integrity issues. Fracture mechanics and non-destructive testing. Stress-corrosion cracking

Nuclear metallurgy Structures and properties of materials with special relevance for nuclear power generation: zirconium and zr-alloys

Pressure vessel and cladding. stainless steel for nuclear applications.

Example of radiation damage in nuclear plant. Stress corrosione cracking and hydrogen embrittlement.

Benjamin M. Ma - Nuclear Reactor Materials and Applications

Gary S. Was - Fundamentals of Radiation Materials Science

W. Hoffelner - Materials for Nuclear Plants

Material supplied by the teacher.

The teaching material, updated year by year by the teacher, is available on a usb support.

The teacher is available with continuity to receive students for solving their learning problems.

The exam is made up of one written test, and one oral test.
The written test consists of two questions, one for each section of the course. It involves a normal classroom, and is two hours long. The written test will be passed if the score for each question is at least 18/30.
The oral test consists of an interview between the candidate and the lecturers. During the test the ability of the candidate to express him/herself in a clear manner using the correct terminology will be also assessed. The oral test will be passed if the score is at least 18/30.
The final score will be the average of the written and oral scores.

The MSc in Nuclear Engineering mainly suggests stages at the end of of the formal education though examinations, favouring the works performed abroad at renown reserach institutions.

For exams, contact luigi2.lazzeri@ing.unipi.it or r.valentini@ing.unipi.it to take engagements.