Hello, everyone!
I can’t understand the units of “scores” accurately. Following shows the explanation of the “kappa-fission” score in User’s Guide[Chapter 8.2]:
It says that the units of “kappa-fission” score are eV per source particle. Following shows the result in tallies.out file. I wanna know the unit of “kappa-fission” rate in tallies.out file.
Similarly, I want to know the unit of “flux” and “fission reaction rate” .etc in tallies.out file.
Besides, About the “Units are eV per source particle”, what on earth the “source particle” means? Does it means the particle in following code?
`
settings = openmc.Settings()
settings.particle = 1000
`
Any replies will be great appreciated !
Best wishes !
D.Benjamin
Hi D.Benjamin,
All tally scores are normalized to the total number of particles that are simulated (usually settings.batches * settings.particles). This ensures that you receive about the same score regardless of how many source particles were simulated. The more particles you simulate, the better the tally estimate will be (i.e., lower uncertainty). Since the kappa-fission score is measuring energy production, the units are eV per source particle. For flux, the units are particle-cm / source particle. If you divide the flux in a region by its volume, you get units of particles / cm^2-source. In a fixed source problem with a known source rate (source particles/sec), multiplying by the source rate gives you the traditional units of particles / cm^2-s. All reaction rate scores are given in reactions per source particle.
Best regards,
Paul
Hi Paul,
I want to ask regarding the units of flux value. How do i know or how do i get the source rate?
Thanks,
Kristina
Hi Kristina,
In a fixed source problem, the source rate is whatever you define it to be. For example, if you know you have a radioactive source that emits 1000 neutrons/sec, that would be the source rate. In a k-eigenvalue problem, it’s a bit trickier to come up with the source rate since it is tied to the power at which the reactor operates. This has been discussed in a previous post, so take a look there for an explanation.
Best regards,
Paul
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