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Division Spotlight
Thermal Hydraulics
The division provides a forum for focused technical dialogue on thermal hydraulic technology in the nuclear industry. Specifically, this will include heat transfer and fluid mechanics involved in the utilization of nuclear energy. It is intended to attract the highest quality of theoretical and experimental work to ANS, including research on basic phenomena and application to nuclear system design.
Meeting Spotlight
2024 ANS Annual Conference
June 16–19, 2024
Las Vegas, NV|Mandalay Bay Resort and Casino
Standards Program
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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Latest News
Direct waste transfer process quickens at Savannah River Site
The Department of Energy Office of Environmental Management’s liquid waste contractor at the Savannah River Site this month marked the first direct transfer of decontaminated waste from the Salt Waste Processing Facility (SWPF) to the Saltstone Production Facility (SPF). This is a new step in optimizing waste processing, according to the DOE.
Alan H. Wells, Albert J. Machiels
Nuclear Technology | Volume 176 | Number 3 | December 2011 | Pages 387-394
Technical Paper | Radiation Transport and Protection | doi.org/10.13182/NT11-A13315
Articles are hosted by Taylor and Francis Online.
According to the U.S. Nuclear Regulatory Commission's guidance based on concerns for potential channeling of neutrons between absorber particles, the criticality safety of transportation systems should not rely on credit for >75% of the boron in fixed neutron absorbers. The 75% efficiency (or effectiveness) factor was first formulated in 1987 for a cask to transport spent fuel from the Fermi Unit 1 (Fermi-1) fast breeder reactor. Fermi-1 fuel was highly enriched (25.6 wt%), and a critical condition could possibly be achieved in a dry environment. The 75% factor was later expanded to include low-enriched light water reactor (LWR) spent fuel, although the latter cannot achieve a critical state without the presence of a moderator. Under flooded conditions, the net effect of channeling is significantly reduced because the neutrons are nearly isotropically scattered by the moderator and impact the neutron absorber from all possible directions. Under dry conditions or under conditions representative in neutron attenuation measurements for absorber qualification, the neutrons impact the absorber mostly perpendicularly, and neutron channeling is maximized. The effect of neutron channeling for the Fermi-1 fuel and for a typical LWR fuel shipment was quantified using a methodology developed to apply experimental transmission data to calculations of the neutron angular distribution at the neutron absorber sheet, yielding the strength of the neutron channeling effect for a particular fuel type and cask basket geometry. These analyses show that neutron absorber qualification via a collimated neutron transmission measurement conservatively bounds the neutron channeling effect. Further imposition of a 75%-only credit leads to an overly conservative amount in neutron absorbers. For transport applications of LWR spent fuel, this results in increased costs with no measurable benefits to criticality safety.