Recent content by ulriksvensson

Yes I solved it the other way around: \rho = 1/N_{a}*sum_{k=1}^{p} M_{k}*N_{k} (Latex code) The reason I was confues was that I forgot to compensate for thermal expansion of the fuel.

Hello everyone. I have a problem I can't figure out. Let's say that we start off with UO2 fuel. Knowing the density (and enrichment) we can calculate the number densities of the constituents (i.e. U-238, U-235, U-234, O-16). Suppose now that the fuel is burned to a certain exposure. A...

I know they used to do this but the difference between these type of calculations and an on-line core follow system can be 50 ppm. That's a lot.

Thanks for your reply. What I meant by unphysical is that for instance you cannot calculate total reactivity by summing up contributions from power defect and rod worths because in reality the problem is non-linear and therefore these calculations are not additive.

Hi forum members. I need some guidance in the following question. In the Studsvik code Simulate-3 you can calculate differnetial and integral rod worths with the input card CRD.OCB. Further, you can specify if you want to lock hydraulics and fission products to some predefined state via the...

Yes, I forgot this. But agree that much of power generation is done by converting heat to electricity, a technology that is about 150 years old. "There's got to be a better way", David Olive.

Yes, I'm a PWR-physicist myself. Every power plant (fossile or nuclear) boils water. Only difference is how. I was more thinking of something that can convert radiation to electricity directly. Kind of like a solar cell. It's done all the time in neutron detectors but I guess it would be...

If we're talking future designs, I'd like to see something that doesn't need to boil water. Or at least better than 35 % efficiency.

Yeah, that's probably it. Should've thought of that. It also explains the phenomenon at coast down when T-in is lowered.

Hi all. I discovered a thing the other day that I've known for a long time but never really thought about. If power distribution is shifted towards the bottom of the core the xenon concentration is shifted towards the top of the core. This is equilibrium conditions, i.e. only very small...

I wouldn't say more susceptible, but a given bow amplitude gives larger local power (i.e for instance radial tilt) in a core made up of 15x15-assemblies than a core made up of 17x17 assemblies. And yes to the second question...

Ok, so if we calculate the ratio between the moderator volume and uranium volume for these two assemblies we get: 15x15: Vm/Vu = 1.4757 17x17: Vm/Vu = 1.4519 This would suggest that 17x17 is more under moderated than 15x15? How does this make cores made up of 15x15 assemblies worse when...

So I'm right when saying that it's the bigger surface that makes the 17x17 less under-moderated? "All" resonance captures occur at the surface of the rod so it seems logical.

Hi all. I need help on an issue I can't figure out. What is the difference between 15x15 and 17x17 fuel when it comes to moderation properties? Standard fuel with these lattices have dimensions 15x15: pitch: 14.3 mm, d_rod: 10.77 mm 17x17: pitch: 12.6 mm, d_rod: 9.5 mm These geometries...

A unitary transformation is one that preserves complex norm, ie complex numbers (or functions) of unit absolute value transforms to complex numbers (or functions) of unit absolute value. If you consider real valued functions of real variables this is the same as orthogonal (or more correctly...