Fission of U-235
Posted: Wed Apr 24, 2019 5:58 am
Dear forum users and developers
I have encountered some FISPACT issues that I’m not able to find any answers to. I am studying the dose rate contribution from specific nuclides arising from fission of U-235.
According to my FISPACT output, all parameters in terms of i.e. nuclide specific activity and heat seem ok, but I get very high dose rate from nuclides with low specific activity. I tried to change different parameters in my FISPACT code to see how the code responded to the change. I changed radiation time, total flux and the amount of U-235 in the source. Here I found something really strange. The change in flux and radiation time responded by change in activity and corresponding dose rate accordingly. But, if flux and radiation time are constants and I only change the amount of U-235 in the source, I get a change in activity but not in dose rate. This may generate nuclides with low specific activity but unreasonable high dose rate contribution. I should also mention that I keep the density constant. Maybe a constant density and larger source (volume) can explain the source self-absorption of gamma radiation, but if I compare activity and dose rate, the results are not realistic.
It seems like dose rate is independent of U-235 mass in the source. This is confusing.
Can someone please explain how to interpret the output results regarding nuclide specific activity vs. nuclide specific dose rate?
Thanks in advance!
/Fredrik
I have encountered some FISPACT issues that I’m not able to find any answers to. I am studying the dose rate contribution from specific nuclides arising from fission of U-235.
According to my FISPACT output, all parameters in terms of i.e. nuclide specific activity and heat seem ok, but I get very high dose rate from nuclides with low specific activity. I tried to change different parameters in my FISPACT code to see how the code responded to the change. I changed radiation time, total flux and the amount of U-235 in the source. Here I found something really strange. The change in flux and radiation time responded by change in activity and corresponding dose rate accordingly. But, if flux and radiation time are constants and I only change the amount of U-235 in the source, I get a change in activity but not in dose rate. This may generate nuclides with low specific activity but unreasonable high dose rate contribution. I should also mention that I keep the density constant. Maybe a constant density and larger source (volume) can explain the source self-absorption of gamma radiation, but if I compare activity and dose rate, the results are not realistic.
It seems like dose rate is independent of U-235 mass in the source. This is confusing.
Can someone please explain how to interpret the output results regarding nuclide specific activity vs. nuclide specific dose rate?
Thanks in advance!
/Fredrik