PSA reactor

PSA Reactor. The idea of a PSA reactor was first suggested by Vaporciyan aud Kadlec (1987 1989). The basic idea is to combine sorption and catalytic reaction in order to shift the thermodynamic equilibrium of the reaction. The sorbent selectively adsorbs one of the products and is regenerated during the low pressure half-cycle. By doing so, the conversion is increased and simultaneous separation is also accomphshed. Vaporciyan and Kadlec (1989) demonstrated the idea for CO oxidation reaction by mixing a 5A zeolite sorbent and a Pt/alumina catalyst in the adsorber. This idea was pursued by Sircar and co-workers (Carvill... 

The Reactor Safety Study was the most important development in PSA because it ... 

When used to identify and evaluate significant risk contributors, as well as to assess the consequences of accident sequences, the PSA provides a comprehensive framework for making many types of decisions regarding reactor design, operation, and siting. These and other appi ications can be facilitated by the rational evaluation of the risks associated with a particular installation. 

As the previous ehapter discussed nuelear power reactor operation and how to perform a PSA on it, this chapter attempts to apply a similar framework to chemical processing. The problem is the diversity of chemical processing that blurs the focus. This chapter begins by showing that accidents in the chemical process industry cost lives and dollars. Descriptions of deadly chemical accidents arc presented to show the chain of sequences that were involved to suggest how their PSA may be structured. Background on selected hazardous chemical process is presented followed by descriptions of how their PSA have structured. The chapter concludes by applying FTAPSUIT to a pressure vessel rupture analysis. 

Regulatory Guide 1.113 provides procedures for estimating the aquatic transport of accidental nd routine releases from nuclear reactors. Because these methods are complex and have not been included in PSAs, they are not discussed. 

PSAs estimate that the frequency of reactor damage cover about two orders of magnitude from about lE-5/y to lE-3/y. This variation is attributable to plant design, construction, and operation, to site characteristics, scope of the PSAs, and methods and analytical assumptions. Such comprehensive studies of comparable chemical process plants do not exist. 

Nuclear PSAs contain considerable uncertainty associated with the physical and chemical processes involved in core degradation, movement of the molten core in the reactor vessel, on the containment floor, and the response of the containment to the stresses placed upon it. The current models of these processes need refinement and validation. Because the geometry is greatly changed by small perturbations after degradation has commenced, it is not clear that the phenomcn.i can be treated. 

The primary motivation of PSAs is to assess the risk of the plant to the public. The immediate purpose of the RSS was to support the Price-Anderson hearings on liability insurance (i.e., assess the financial exposure of a nuclear power reactor operator) a purpose which, even today, is beyond PSA technology. However, PSA is sufficiently precise to provide relative risk comparisons of reactor designs and sites. These uses of PSA were presented at the Indian Point hearings, and in defense of Shoreham. The PSAs for the high-population-zone plants (Limerick, Zion, and Indian Point) were prepared to show that specific features of these plants compensate for the higher population density relative to plants studied in the RSS. 

In the first 2.5 years of the precursor study, 169 significant precursors were identified for ihe 4. i2 reactor-years of operating experience represented by LERs submitted from 1969 to 1979. preliminary findings show 56 precursors for 126 reactor-years of operating experience for 1980-1981. The results were used to analyze accident sequences to estimate core melt frequencies lor operating plants and to compare these results with the estimates in existing PSAs. 

In the U.S., the Department of Energy operates or has operated reactors that are used for nuclear physics, materials studies, and i.sotope production. Their safety has been assessed by PSA. 

In May 1988, a Level-1 PSA was undertaken as part of the general risk assessment at DOE facilities. Revision 0 was completed, and reviewed by BNL, DOE and contractors. The revised report was available July 1990 (Azarm, 1990). The broad objective of the HFBR PRA program is to enhance the safety and operational activities throughout the. remaining lifetime of the reactor... 

The external events PSA was based on standard methods used for commercial reactor PSAs, Fire risk was estimated from commercial nuclear power plant data combined with industrial fire information. The seismic hazard was evaluated using a combination of the EPRI and LLNL ( UREG/CR-.3250) databases. Wind hazards were analyzed by EQE, Inc., using NRC-based nicihodulogy. 

Atkinson. S. A., 1996, PSA-Operations Synergisms for Advanced Test Reactor Shutdown Operations PSA, Proceeding of the Int ——1 Topical Meeting on Probabilisl ety Assessment, Park City, Utah, pp 600-6 29-Oct. 3. 

Individual Plant Examinations Perspectives on Reactor Safety, PSA-96... 

There had been small-scale probabilistic risk studies, but the first in-depth study v, as initiated by the U.S, Atomic Energy Commission in September 1972 and completed by the Nuclear Regulatory Commission (NRC). This was known as the Reactor Safety Study, W. SH-(400, Ociuher 1975) that set the pattern for subsequent PSAs not only nuclear, but chemical md tniii portation, PSA had it beginnings in nuclear power because of the unknown risk and the large amounts of funds for the investigation. 

There is a close kinship between the chemical process industry and the nuclear electric power industry. In tact once the physics of nuclear reaction was established the rest is chemistiy and hc.it ii an.sfer. The word "reactor" is from chemistry for the location the reaction takes place.. nuclear reactor consists of a vessel in which a nuclear reaction heats water to make steam to drive a turbine o generate electricity. Thus the primary components are pipes, valves, pumps heat exchangers, and water purifiers similar to the components found in a chemical plant. Following the success of WASH-1400, PSA was used to analyze the chemical proce.ssmg of nuclear fuel and. aste preparation for disposal. 

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