Self powered neutron detector with Vanadium-51 used to measure thermal neutron flux in our TRIGA MARK II reactor. Another question is, how to determine the conversion factor of current produced by emitted beta in 51V(n, beta)52Cr reaction to neutron flux unit [neutron/cm-2.s-1]?
Hi Mohamad,
For the first part of the question, I don't think so. The processes are separate, i.e. neutron activation produces V-52, which then beta decays into Cr-52. The answer for the second part is more complicated. One way to determine the "conversion factor" is through Monte Carlo calculations. You will find more information e.g. here: L. Barbot et al., Calculation to Experiment Comparison of SPND Signals in Various Nuclear Reactor Environments and L. Vermeeren, Neutron and Gamma Sensitivities of Self-Powered Detectors: Monte Carlo Modelling (both are conference papers, presented at ANIMMA 2015). Alternatively, you could obtain a "conversion factor" by calibrating the SPND response against activation measurements. However, depending on the SPND design etc., there may be a significant contribution from gamma rays to the total SPND response, and this conversion factor may not be exactly the same throughout the reactor.
Hope this helps,
Vladimir
First of all the correct reaction is 51V(n,gamma)52V. Now since 52V is a beta-emitter, it decays to 52Cr. So these two processes (neutron capture and beta emission) are entirely independent. Both are also independent of the energy of the inident neutron (we denote it by En). The magnitude of En can only influence the cross section of the neutron capture reaction. Tlhe decay time of 52V is ~ 3.7 min. So it is not at all clear what do you mean by the current of electrons emitted by 52V. Can you elaborate?
Yes, it is V-52 decay by beta emission to Cr-52. Thank you for the explanation. This mean, it all depend on the capture cross section. I did some simulation on V-51 sensitivity on neutron spectrum in our reactor. Based on this results, I can determine the neutron energy range that contributes signals to the Vanadium SPND.
I agree with previous statements, but I want to be more cautious.
Your neutron-induced reaction forms 52V in its excited state. It first have to decay to its ground state via isomeric transitions, and then decay to 52Cr by beta decay. If there is a "long-lived" isomer in the 52V level scheme, it can decay to 52Cr directly (feeding different levels than in the "standard" 52V decay).
When looking to the 52V level scheme, it seems that there is not a lot of these long-lived isomers, and all of these decay only to the 52V ground state. But on the other hand, there is not a lot of information about fast-neutron induced formation of 52V.
So my conclusion would be : in your simulations and assumptions it is normal to consider your spectrum to be independent of the indicent neutron energy. But if you observe something very strange in your experimental data, keep in mind that this dependancy may exist.
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