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EPA issues final rule regulating “forever chemicals”
The Environmental Protection Agency announced that it will issue a rule aimed at limiting public exposure to per- and polyfluoroalkyl substances (PFAS). The final rule will designate two widely used PFAS chemicals, perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS), as hazardous substances under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), also known as Superfund.
According to the EPA, both PFOA and PFOS meet the statutory criteria for designation as hazardous substances.
Robert Petroski, Benoit Forget, Charles Forsberg
Nuclear Technology | Volume 175 | Number 2 | August 2011 | Pages 388-400
Technical Paper | Fuel Cycle and Management | doi.org/10.13182/NT11-A12311
Articles are hosted by Taylor and Francis Online.
In a breed-and-burn (B&B) reactor, the reactor is first started with enriched uranium or other fissile material but thereafter can be refueled with natural or depleted uranium. B&B reactors have the potential to achieve >10% uranium utilization in a once-through fuel cycle versus <1% for light water reactors. A newly developed method for analyzing B&B reactors - the "neutron excess" concept - is used to determine the minimum amount of startup fuel needed to establish a desired equilibrium cycle in a minimum burnup B&B reactor. Here, a minimum burnup B&B reactor is defined as one in which neutron leakage is minimized and feed fuel can be discharged at uniform burnup. The neutron excess concept reformulates the k-effective of a system in terms of material depletion quantities: the total number of neutrons absorbed and produced by a given volume of fuel, which are termed "neutron excess quantities." This concept is useful because neutron excess quantities are straightforward to estimate using simple one-dimensional (1-D) and zero-dimensional (0-D) models. A set of equations is developed that allows the quantity of starter fuel needed to establish a given B&B equilibrium cycle to be expressed in terms of neutron excess quantities. A simple 1-D example of a sodium-cooled, metal fuel reactor with a startup enrichment of 15% is used to illustrate how the method is applied. An estimate for the required amount of starter fuel based on a 0-D depletion model is found to differ by only 3% from the actual amount computed using the 1-D example model.