Delayed neutrons

Definition

Delayed neutrons are neutrons that are emitted from fission products in a nuclear reaction after a brief delay, typically on the order of seconds to minutes. These neutrons play a crucial role in the control of nuclear reactors because they allow for a more manageable response to changes in reactor conditions, enhancing safety and efficiency.

5 Must Know Facts For Your Next Test

1. Approximately 0.5% to 0.7% of neutrons produced in fission reactions are delayed neutrons, significantly impacting reactor control.
2. The presence of delayed neutrons allows for more gradual changes in reactor power levels, providing operators time to respond to fluctuations.
3. Delayed neutron emission is vital for maintaining a controlled chain reaction, as it helps to stabilize the reactor's criticality.
4. Different isotopes of fission products release delayed neutrons with varying half-lives, influencing reactor design and operation.
5. The study of delayed neutrons was crucial for the development of early nuclear reactors, as it enhanced our understanding of neutron behavior and reactor kinetics.

Review Questions

• How do delayed neutrons contribute to the stability and control of a nuclear reactor?
  • Delayed neutrons contribute significantly to the stability and control of a nuclear reactor by allowing operators to manage power levels more effectively. Since these neutrons are emitted after a delay, they provide a buffer period for adjustments in reactor conditions, enabling operators to respond appropriately to any changes. This characteristic helps prevent rapid fluctuations in reactor power, enhancing overall safety and operational efficiency.
• Compare and contrast delayed neutrons with prompt neutrons in terms of their roles in a nuclear fission reaction.
  • Delayed neutrons and prompt neutrons differ primarily in their timing and impact on reactor operations. Prompt neutrons are emitted immediately during fission, initiating the chain reaction and contributing to immediate energy release. In contrast, delayed neutrons are released from fission products after a brief period, allowing for better control over the reactor's power output. Together, they balance each other; prompt neutrons drive the reaction while delayed neutrons provide a mechanism for stabilization.
• Evaluate the significance of delayed neutron research in the advancement of nuclear technology and safety measures.
  • Research on delayed neutrons has been pivotal in advancing nuclear technology and improving safety measures in reactors. Understanding how delayed neutrons behave allows engineers to design reactors that can better handle fluctuations in power levels and maintain criticality safely. This knowledge has led to more reliable reactor designs, increased operational safety protocols, and effective response strategies during potential emergencies, ultimately contributing to the safe use of nuclear energy worldwide.

Related terms

Prompt neutrons: Prompt neutrons are the neutrons that are emitted almost instantaneously during the fission process, providing the initial burst of radiation that contributes to the chain reaction.

Fission products: Fission products are the radioactive isotopes that result from the splitting of heavy nuclei during fission, which can decay and emit delayed neutrons.

Neutron flux: Neutron flux refers to the intensity of neutron radiation in a given area, which is crucial for understanding the behavior of a nuclear reactor and its criticality.