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Nuclear Criticality Safety
NCSD provides communication among nuclear criticality safety professionals through the development of standards, the evolution of training methods and materials, the presentation of technical data and procedures, and the creation of specialty publications. In these ways, the division furthers the exchange of technical information on nuclear criticality safety with the ultimate goal of promoting the safe handling of fissionable materials outside reactors.
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The Standards Committee is responsible for the development and maintenance of voluntary consensus standards that address the design, analysis, and operation of components, systems, and facilities related to the application of nuclear science and technology. Find out What’s New, check out the Standards Store, or Get Involved today!
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Siting of Canadian repository gets support of tribal nation
Canada’s Nuclear Waste Management Organization (NWMO) announced that Wabigoon Lake Ojibway Nation has indicated its willingness to support moving forward to the next phase of the site selection process to host a deep geological repository for Canada’s spent nuclear fuel.
Azin Behdadi, John C. Luxat
Nuclear Technology | Volume 181 | Number 1 | January 2013 | Pages 157-169
Technical Paper | Special Issue on the 14th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-14) / Fission Reactors; Reactor Safety; Thermal Hydraulics | doi.org/10.13182/NT13-A15764
Articles are hosted by Taylor and Francis Online.
Heavy water moderator surrounding each fuel channel is one of the important safety features in CANDU reactors since it provides an in situ passive heat sink for the fuel in situations where other engineered means of heat removal from fuel channels have failed. In a critical-break loss-of-coolant-accident scenario, fuel cooling becomes severely degraded because of rapid flow reduction in the affected flow pass of the heat transport system. This can result in pressure tubes (PTs) experiencing significant heatup during early stages of the accident when coolant pressure is still high, thereby causing uniform thermal creep strain (ballooning) of the PT in contact with its calandria tube (CT). The contact of the hot PT with the CT causes rapid redistribution of stored heat from the PT to the CT and a large heat flux spike from the CT to the moderator fluid. For conditions where subcooling of the moderator fluid is low, this heat flux spike can cause dryout of the CT. This can detrimentally affect channel integrity if the CT postdryout temperature becomes sufficiently high to result in continued thermal creep strain deformation of both the PT and the CT. The focus of this work is to develop a mechanistic model to predict critical heat flux (CHF) on the CT surface following a contact with its PT. A COMSOL multiphysics model using a two-dimensional transient fluid-thermal analysis of the CT surface undergoing heatup is used to predict the flow and temperature profiles on the CT surface. A mechanistic CHF model is to be proposed based on a concept of wall dry patch formation, prevention of rewetting, and subsequent dry patch spreading.