Reactor operation (Practicals) - 5PMGEXP4

Goal(s)

The objective of the design study on the normal operation of a Pressurized Water Reactor using the SIREP simulator is to:
• Understand operating procedures from cold shutdown to hot shutdown (155 bars, 297°C) using the P/T diagram, before reactor startup.
• Justify how primary temperature and pressure are controlled depending on P/T conditions.
• Understand the behavior of a subcritical core in the presence of neutron sources.
• Grasp the principle of the subcritical approach (without reactivity information) while avoiding unintended criticality.
• Understand the behavior of a diverged core, whether supercritical or subcritical, at "zero power", i.e., below the nuclear heating threshold (commonly but improperly referred to as the "Doppler threshold").
• Understand and model the behavior of the diverged core "at power" (beyond the nuclear heating threshold, as soon as heating is observed).
• Grasp the importance of thermal feedback effects for reactor safety.
• Understand zero-power physics tests performed during startup to measure certain core neutronic characteristics and compare them with those calculated during core reload safety evaluations.
• Illustrate the moderator effect through a partial realization of one of the startup physics tests: measurement of the isothermal temperature coefficient (?_iso) and its evolution as a function of boron concentration.
• Understand the primary–secondary loop interaction, explaining how a PWR is operated and why a secondary-side incident can lead to a reactivity accident.
• Understand and model the "at power" core behavior before and after grid connection.
• Once connected, understand turbine-following operation, the "natural" core behavior (without control rod movement), and the concept of load-following mode.
• Understand the temperature control program Tm & Tv = f(%Pn) and the benefit of regulating the average primary temperature using control rods (R group).
• Understand the origin of various reactivity effects and how they are controlled during load-following operations (boron/control rod distribution).
• Understand the origin of operational limits to be respected: those directly linked to the power–?Pax relationship (pilot diagram), and those linked to "core margins": "low REC" and "linear overpower".
• Understand the limits of the boron dilution system as the cycle progresses, and how cycle extension is handled when the CB becomes too low.
• Finally, be able to summarize the advantages and disadvantages of the two main reactivity control methods (boron/control rods).

Content(s)

• First session (4 hours):
Chapter 1 – Progression on the P/T diagram before reactor startup

• Second session (4 hours):
Chapter 2 – Subcritical approach and startup
Chapter 3 – Identifying the nuclear heating threshold

• Third session (4 hours):
Chapter 4 – Zero-power physics tests
Chapter 5 – Unit startup and grid connection (Part 1)

• Fourth session (4 hours):
Chapter 5 – Unit startup and grid connection (Part 2)
Chapter 6 – Power operation and load-following

This course is taught in English/French. A visit to an EDF-operated nuclear power plant is scheduled at the end of the course.

• Operation of Pressurized Water Reactors (PWR): basic principles and main systems
• Reactor kinetics and dynamics
• Reactor physics and neutron transport
• Single-phase and two-phase thermohydraulics