# Neutron transport equation and pressure drop calculations in core ...

• sehrish shakir
In summary, Pressure drop calculations in core differ from one fuel rod to the entire core. The main difference is that in calculating the pressure drop across one fuel rod, the resistance of the fuel rod is taken into account whereas in calculating the pressure drop across the entire core, the resistance of the entire core is taken into account.

#### sehrish shakir

i am a physicist now i am doing Ms in nuclear engineering ... i need to understand basic concepts ...
neutron transport equation ? what is the transport phenomenon actually ?

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sehrish shakir said:
i am a physicist now i am doing Ms in nuclear engineering ... i need to understand basic concepts ...
neutron transport equation ? what is the transport phenomenon actually ?
Those are two broad areas. I would imagine that one will take courses in reactor theory and fluid mechanics in which one would learn both subjects.

A fission reaction releases 2 or 3 neutrons in addition to the two fission product radionuclides and gamma radiation. Some fission products also release neutrons, and that population is called 'delayed neutrons' which allow for control of the reactor during withdrawal of control rods. Fission neutrons are born with energies in the low MeV range, and they must be slowed or 'moderated' to less the 0.1 eV, or 7-8 orders of magnitude in energy to increase the probability of causing additional fissions. Transport theory and its approximation, diffusion theory, addresses how a population of neutrons behave in a reactor environment.

Fluid mechanics describes how fluids behave when flowing through structures such as pipes, or in the case of a reactor, through the core. The fuel assemblies impose a resistance, or drag, on the coolant. The pressure, in conjunction with temperature, is important as it influences the heat transfer mechanism, forced convection, and it is important in pressurized water reactors (PWRs) to limit nucleate boiling toward the top of the core (the coolant condition must remain below the point of departure from nuclear boiling, DNB), whereas in boiling water reactors (BWRs) must remain below a critical power at which boiling transition, or dryout, occurs.

• sehrish shakir
Astronuc said:
Those are two broad areas. I would imagine that one will take courses in reactor theory and fluid mechanics in which one would learn both subjects.

A fission reaction releases 2 or 3 neutrons in addition to the two fission product radionuclides and gamma radiation. Some fission products also release neutrons, and that population is called 'delayed neutrons' which allow for control of the reactor during withdrawal of control rods. Fission neutrons are born with energies in the low MeV range, and they must be slowed or 'moderated' to less the 0.1 eV, or 7-8 orders of magnitude in energy to increase the probability of causing additional fissions. Transport theory and its approximation, diffusion theory, addresses how a population of neutrons behave in a reactor environment.

Fluid mechanics describes how fluids behave when flowing through structures such as pipes, or in the case of a reactor, through the core. The fuel assemblies impose a resistance, or drag, on the coolant. The pressure, in conjunction with temperature, is important as it influences the heat transfer mechanism, forced convection, and it is important in pressurized water reactors (PWRs) to limit nucleate boiling toward the top of the core (the coolant condition must remain below the point of departure from nuclear boiling, DNB), whereas in boiling water reactors (BWRs) must remain below a critical power at which boiling transition, or dryout, occurs.
thank you very much i have taken a course on fluid mechanics but i think i was unable to understand it well ... as our class consists of mechanical engg as well as scientists so the very basic knowledge was not provided so i was unable to handle problems in paper ... i need to understand the deep concepts and how to solve the given problems ... i am studying reactor theory courses in this semester hopefully i will be able to understand the concept very well ...

Respectable @Astronuc
thank you for the kind response sir,
please if you can provide help regarding pressure drop calculation mentioned in kazmi book ?
question is what is the main difference in calculating the pressure drop across one fuel rod and entire core .
chap #9 single phased fluid mechanics ...

## 1. What is the neutron transport equation and why is it important in core calculations?

The neutron transport equation is a mathematical model used to describe the behavior of neutrons in a nuclear reactor core. It takes into account various factors such as neutron flux, energy, and direction to predict how the neutrons will interact with the reactor materials. This equation is important in core calculations because it allows scientists to understand and predict the performance of a nuclear reactor.

## 2. How is the neutron transport equation solved?

The neutron transport equation is a complex equation that cannot be solved analytically. Therefore, scientists use numerical methods such as Monte Carlo simulations or deterministic methods like the discrete ordinates method to solve it. These methods break down the equation into smaller, solvable parts and then combine the results to obtain a solution.

## 3. What is pressure drop and why is it important in core calculations?

Pressure drop is the decrease in fluid pressure as it flows through a system, such as a nuclear reactor core. It is an important factor in core calculations because it affects the flow rate and distribution of coolant, which can impact the reactor's performance and safety. A higher pressure drop may result in lower efficiency or even damage to the reactor components.

## 4. How is pressure drop calculated in a nuclear reactor core?

Pressure drop in a nuclear reactor core is calculated using the Bernoulli's principle, which states that the total energy of a fluid is conserved along a streamline. This principle is applied to the fluid flow in the reactor, taking into account factors such as fluid density, velocity, and geometry of the core. The resulting equation can be solved to determine the pressure drop in the core.

## 5. What factors can affect the accuracy of neutron transport equation and pressure drop calculations?

Several factors can affect the accuracy of neutron transport equation and pressure drop calculations in a nuclear reactor core. These include uncertainties in the input parameters, such as neutron cross-sections and material properties, as well as limitations of the chosen numerical methods. Other factors may include changes in reactor operating conditions or unforeseen events, which can impact the accuracy of the calculations and require further analysis and validation.