Effects of Nitric Acid on Criticality Safety Analysis
- Savannah River Nuclear Solutions (SRNS), Aiken, SC (United States)
As nitric acid molarity is increased, there are two competing phenomena affecting the reactivity of the system. First, there is interaction between each of the 10 wells in the basket-like insert. As the molarity of the nitric acid solution is increased (it moves from 100% water to 100% HNO3), the hydrogen atom density decreases by about 80%. However, it remains a relatively efficient moderator. The moderating ratio of nitric acid is about 90% that of water. As the media between the wells is changed from 100% water to 100% nitric acid, the density of the media increases by 50%. A higher density typically leads to a better reflector. However, when the macroscopic scattering cross sections are considered, nitric acid is a much worse reflector than water. The effectiveness of nitric acid as a reflector is about 40% that of water. Since the media between the wells become a worse reflector and still remains an effective moderator, interaction between the wells increases. This phenomenon will cause reactivity to increase as nitric acid molarity increases. The second phenomenon is due to the moderating ratio changing in the high concentration fissile-nitric acid solution in the 10 wells. Since the wells contain relatively small volumes of high concentration solutions, a small decrease in moderating power has a large effect on reactivity. This is due to the fact that neutrons are more likely to escape the high concentration fissile solution before causing another fission event. The result of this phenomenon is that as nitric acid molarity increases, reactivity decreases. Recent studies have shown that the second phenomenon is indeed the dominating force in determining reactivity changes in relation to nitric acid molarity changes. When considering the system as a whole, as nitric acid molarity increases, reactivity decreases.
- Research Organization:
- Savannah River Nuclear Solutions (SRNS), Aiken, SC (United States)
- Sponsoring Organization:
- USDOE National Nuclear Security Administration (NNSA), Nuclear Criticality Safety Program (NCSP)
- DOE Contract Number:
- AC09-08SR22470
- OSTI ID:
- 1024397
- Report Number(s):
- SRNS-STI-2011-00484; TRN: US201119%%353
- Resource Relation:
- Conference: ICNC '99: International Conference on Nuclear Criticality, Edinburgh, Scotland (United Kingdom), 19-22 Sep 2011
- Country of Publication:
- United States
- Language:
- English
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