Chapters 4.1-4.3

This flashcard set covers key concepts related to power reactors, including their core layout, types, fuel assemblies, reactor operations, and the impacts of material choices on reactor behavior.

What are the main objectives when examining the power reactor core?

To examine core layouts, relate heat transport and neutronic behavior, explain the impact of reactor lattice structure on neutronics, and understand its effect on multiplication factor.

What two main factors determine the composition of a reactor?

1) Criticality must be maintained over required power levels and core life; 2) Design must allow heat from fission to be transferred out without overheating.

What are common coolant types used in reactors?

Water is the most common coolant used in light water reactors, while heavy water is used in CANDU reactors.

Why are fuel assemblies necessary in a reactor?

Fuel assemblies group together fuel elements to facilitate efficient refueling and operation.

What is the typical allowable linear heat rate for fuel elements?

Typically falls between a few and tens of kW/m.

What is the function of the pressurizer in a PWR?

It prevents coolant boiling at operating temperatures by maintaining the pressure in the reactor vessel.

How does a BWR differ from a PWR in coolant operation?

BWRs operate at lower pressures and allow boiling to take place in the coolant channels.

What is the significance of doping levels in heavy water reactors like CANDU?

CANDU reactors require enriched fuel to sustain the necessary burn-up rates for efficient reactor operation.

What is unique about the fuel used in HTGRs?

HTGRs use graphite and ceramic materials in the core, which enables high coolant temperatures.

What is the primary coolant used in fast reactors?

Liquid metals are the most widely used coolant for fast reactors due to their excellent heat transfer properties.

How does the nuclear multiplication factor k relate to core volume?

PNL approaches one as core volume increases, impacting overall reactivity and criticality.

What happens to the neutron energy spectrum when low atomic weight materials are present in a reactor?

The presence of low atomic weight materials degrades the neutron energy spectrum.

How does enrichment affect fast reactor multiplication?

The ratio of nuclide absorption cross sections leads to increased multiplication with higher enrichment of fissile material.

What is the role of structural materials in a reactor core?

Structural materials can absorb neutrons, thereby decreasing k∞ and affecting the reactor's criticality.

What characterizes the lattice structures used in fast reactors?

Fast reactors employ hexagonal lattice cells allowing for smaller volume ratios of coolant to fuel.

Describe the function of fuel elements in a power reactor.

Fuel elements produce thermal energy through fission, which is then transferred to the coolant.

What is the difference between thermal and fast reactors in terms of fuel enrichment?

Fast reactors generally require higher levels of fuel enrichment, typically exceeding 10%, compared to thermal reactors.

What are the main objectives when examining the power reactor core?

To examine core layouts, relate heat transport and neutronic behavior, explain the impact of reactor lattice structure on neutronics, and understand its effect on multiplication factor.

What two main factors determine the composition of a reactor?

1) Criticality must be maintained over required power levels and core life; 2) Design must allow heat from fission to be transferred out without overheating.

What are common coolant types used in reactors?

Water is the most common coolant used in light water reactors, while heavy water is used in CANDU reactors.

Why are fuel assemblies necessary in a reactor?

Fuel assemblies group together fuel elements to facilitate efficient refueling and operation.

What is the typical allowable linear heat rate for fuel elements?

Typically falls between a few and tens of kW/m.

What is the function of the pressurizer in a PWR?

It prevents coolant boiling at operating temperatures by maintaining the pressure in the reactor vessel.

How does a BWR differ from a PWR in coolant operation?

BWRs operate at lower pressures and allow boiling to take place in the coolant channels.

What is the significance of doping levels in heavy water reactors like CANDU?

CANDU reactors require enriched fuel to sustain the necessary burn-up rates for efficient reactor operation.

What is unique about the fuel used in HTGRs?

HTGRs use graphite and ceramic materials in the core, which enables high coolant temperatures.

What is the primary coolant used in fast reactors?

Liquid metals are the most widely used coolant for fast reactors due to their excellent heat transfer properties.

How does the nuclear multiplication factor k relate to core volume?

PNL approaches one as core volume increases, impacting overall reactivity and criticality.

What happens to the neutron energy spectrum when low atomic weight materials are present in a reactor?

The presence of low atomic weight materials degrades the neutron energy spectrum.

How does enrichment affect fast reactor multiplication?

The ratio of nuclide absorption cross sections leads to increased multiplication with higher enrichment of fissile material.

What is the role of structural materials in a reactor core?

Structural materials can absorb neutrons, thereby decreasing k∞ and affecting the reactor's criticality.

What characterizes the lattice structures used in fast reactors?

Fast reactors employ hexagonal lattice cells allowing for smaller volume ratios of coolant to fuel.

Describe the function of fuel elements in a power reactor.

Fuel elements produce thermal energy through fission, which is then transferred to the coolant.

What is the difference between thermal and fast reactors in terms of fuel enrichment?

Fast reactors generally require higher levels of fuel enrichment, typically exceeding 10%, compared to thermal reactors.