What is the UFTR effective delayed neutron fraction at End of Life (EOL)?

What is the UFTR effective delayed neutron fraction at End of Life (EOL)?

• A. 739
• B. 741
• C. 750
• D. 730

Answer: (A)

The effective delayed neutron fraction is the portion of neutrons produced from delayed neutron precursors that actually contribute to sustaining the fission chain reaction, after accounting for leakage and spectral effects. It’s a small fraction, typically expressed in pcm (parts per 100,000 neutrons). For UFTR at End of Life, the isotopic inventory from burnup places beta_eff around 0.00739, which is 739 pcm. This value sits in the 730–750 pcm range, and 739 pcm is the standard reference used for UFTR EOL data. The other nearby numbers are close but do not match the established UFTR EOL value as closely. This parameter matters because it governs how the reactor responds to reactivity changes: the more the delayed-neutron fraction, the slower the reactor responds, since delayed neutrons provide a buffering effect in kinetics.

The effective delayed neutron fraction is the portion of neutrons produced from delayed neutron precursors that actually contribute to sustaining the fission chain reaction, after accounting for leakage and spectral effects. It’s a small fraction, typically expressed in pcm (parts per 100,000 neutrons).

For UFTR at End of Life, the isotopic inventory from burnup places beta_eff around 0.00739, which is 739 pcm. This value sits in the 730–750 pcm range, and 739 pcm is the standard reference used for UFTR EOL data. The other nearby numbers are close but do not match the established UFTR EOL value as closely.

This parameter matters because it governs how the reactor responds to reactivity changes: the more the delayed-neutron fraction, the slower the reactor responds, since delayed neutrons provide a buffering effect in kinetics.