MCNP terminology question -- Effective Full Power Days (EFPDs)

[Rofida]

TL;DR Summary

the term EFPDs

for MCNP users, i would like to ask about terminologies: if i depleted a fuel assembly under constant power, is the number of days in the out can be used as Effective Full Power Days (EFPDs), or this term has another specific meaning?

 

[Astronuc]

Effective Full Power Days (EFPD) or Effective Full Power Hours (EFPH) are useful for calculating burnup in terms of MWd/kgU, or GWd/tU, or GWd/tHM. If a reactor operates at 50% power for 1 day, then that would give 0.5 EFPD, or 12 EFPH. Similarly, if a reactor operated at 80% of full power for one day, then that would give 0.8 EFPD, or 19.2 EFPH. If the power is varied over a day, then one could use the trapezoidal rule to calculate the equivalent EFPD or EFPH.

Note that some folks like to calculate with EFPH, and some use burnup in terms of mass of UO₂ rather than mass of metal.

In fuel performance, some properties and behavioral models are dependent on burnup, e.g., thermal conductivity of the fuel, while other properties, e.g., growth, strength and ductility of the Zr-alloy cladding, depend on fast fluence (and temperature).