BUSN20016 Research in Business: Nuclear Safety and Criticality Safety

1.

The Idaho Chemical Plant Accident of 16^th October 1959 was a result of an error that occurred during the siphoning of the fissile material solution of uranyl nitrate. The error in the siphoning process caused a transfer of some of the solution from the tank it was contained in to a separate tank containing water. The reaction between the fissile material and the water resulted in the formation of uranyl nitrate crystals with much of the water evaporated. Airborne fission material released during the accident affected 19 individuals, 2 of them with significantly high doses and smaller doses for the remaining 17 individuals. The accident occurred despite the plant having cylindrical vessels with favorable geometry. The absence of an anti-siphon device, operator’s unfamiliarity of processes and operating procedures that were not up to date, were cited as the major causes of the accident (Thomas, Shean, V, Boris, & Victor, 2000).

The effects of these accidents have impacted the nuclear industry negatively. The health effects from exposure to airborne fissile material may discourage people from pursuing nuclear related careers. This reduces the number of experts in the nuclear industry. The accidents lead to financial loses when equipment is damaged, for countries and private investors alike. This might as well discourage further investment into the industry. The effects of these accidents also have an immense impact on the public perceptions, opinions and attitudes towards nuclear energy, a factor that may result in governments and investors pulling away from the industry.        

The Nuclear Criticality Safety has improved over time, characterized by a huge decrease in criticality accidents. Since the start of the nuclear industry, Nuclear Criticality Safety has moved from being sets of safety standards for nuclear criticality, to becoming a discipline on its own. This has showed its importance in the nuclear industry, which has also been emphasized by the American Nuclear Society (ANS) through the formation of the Nuclear Criticality Safety Technical Group in 1967 and later on in 1970 made Nuclear Criticality Safety a division within the organization. In addition, at the onset of the nuclear industry data was understandably lacking. Information relevant to criticality such as factors contributing to Keff, significant margins of safety and administrative controls did not exist. The early experiments on criticality then formed the standard practice in the industry, although the information from these experiments was not sufficient enough. With time however, the increased information from the experiments allowed for the development of geometrical safe containers for the fissile materials. Presently, data available in databases such as Spent Fuel Isotopic Composition Database and the Criticality Benchmark Experiments have been instrumental in providing detailed information on safety standards that characterize modern day Nuclear Criticality Safety.         

2.

The IAEA counterpart to the US Criticality Safety Standards ANSI/ANS 8 series is the IAEA Safety Standards Series No. SSG-27.

The main platform for sharing of information related to nuclear criticality safety is the International Atomic Energy Agency (IAEA). This is an agency of the United Nations that is handles matters regarding atomic energy. Member states of the United Nations, that produce nuclear energy, can present reports of findings on nuclear criticality safety to IAEA, thereby helping in better understanding of steps necessary in providing nuclear criticality safety.

Regional organizations are also crucial institutions that assist in the sharing of information on nuclear criticality safety. The regional organizations usually have departments within them that are dedicated to atomic energy, more like what IAEA is for the United Nations. These provide avenues for allied countries to exchange information on the best practices in nuclear criticality safety. This becomes vital sharing platforms especially for instances where countries want to protect their nuclear technology from non-allied countries.

Education Institution that specialize in nuclear energy also form avenues for exchange of knowledge on nuclear criticality safety. Institutions such as the European Nuclear Education Network Association and European Nuclear Safety Training Institute provide opportunity for experts in the field of nuclear and atomic energy to share information on the latest safety procedures in the field. Lectures, talks and conferences can be organized by these institutions to invite experts from the countries producing nuclear energy to talk about the relevant safety measures.

3.

MERMAIDS is an acronym for the Nuclear Criticality Safety parameters. The parameters in this acronym are: Mass, Enrichment, Reflection, Moderation, Absorption, Interaction, Density and Concentration, and Shape.

For nuclear fission and by extension criticality to occur, there is a minimum mass of the fissile material required. Maintaining the mass below this mass ensures criticality doesn’t occur. (American Nuclear Society, 2006)

Highly enriched fissile material increase the chances for criticality. Therefore, using averagely enriched fissile material helps in preventing occurrence of criticality.

Materials such as tungsten, lead and carbon are good reflectors and increase the chances of criticality. Reducing the amounts of these materials or substituting them with less reflective ones will stop occurrence of criticality. (James, 2008)

Moderators just like reflectors accelerates criticality through collision with the atomic nuclei. Thus minimizing their use or substituting reduces the probability of criticality occurring. (Knief, 1985)

Absorbers remove the neutrons from the reaction system. Therefore, injecting absorbers, such as indium, in the system help in reducing criticality occurrences.

Increasing the distance between subcritical systems reduces the chance of interaction between the systems which would otherwise cause criticality in both systems. (Irving, 1962).

Fissile materials with high densities have less leakage of neutrons, this increases the occurrence of fission in them. To reduce this occurrence, and hence reduce criticality, materials with low densities should be used.

Neutrons are more likely to leak from materials with large surface areas. This leakage reduces the chances of criticality occurring. Hence, using fissile materials that have shapes with broad surfaces reduces criticality occurrences (Jay, 2008) 

References

American Nuclear Society. (2006). Oklo's Natural Fission Reactors. American Nuclear Society, 28.

Irving, K. (1962). Introductory Nuclear Physics 2nd Edition. London: Addison- Wesley.

James, M. E. (2008). Nuclear Criticality. New York.

Jay, N. (2008). Physics of the Life Sciences. New York: Springer.

Knief, R. A. (1985). Nuclear Criticality Safety: Theory and Practice. American Nuclear Society Softcover, 236.

Thomas, M. P., Shean, M. P., V, V. F., Boris, R. G., & Victor, S. I. (2000). A Review of Criticality Accidents. 2000 Revision.