Safety reactor, thermodynamics

Reactor safety analysis, thermodynamics of Pu-oxygen system 109-21... 

In Section 11.2, general principles of reactor safety and heat balance of reactors are presented, with an emphasis on specific aspects of polymerizations. Section 11.3 is devoted to safety-related thermodynamics and reaction engineering aspects of polymerization reactions. In Section 11.4, cooling of polymerization reactors is reviewed. The chapter is concluded by a section describing safety aspects of industrial processes, together with technical risk-reducing solutions. 

This paper reviews data on certain thermodynamic aspects of the nonstoichiometric Pu-0 system, which may serve as a basis for use In reactor safety analysis. Emphasis Is placed on phase relationships, vaporization behavior, oxygen-potential measurements, and evaluation of pertinent thermodynamic quantities. Limited high temperature oxygen potential data obtained above the fluorite, diphasic, and sesquioxide phases In the Pu-0 system are presented. 

In considering the operational safety and accident analyses of sodium-cooled fast reactors, similar information on the release of fission products from sodium is needed. Although the extent of vaporization can often be calculated from thermodynamic considerations (3, 4), appropriate transport models are required to describe the rate phenomena. In this chapter the results of an analytical and experimental investigation of cesium transport from sodium into flowing inert gases are presented. The limiting case of maximum release is also considered. 

Part I gives a general introduction and presents the theoretical, methodological and experimental aspects of thermal risk assessment. The first chapter gives a general introduction on the risks linked to the industrial practice of chemical reactions. The second chapter reviews the theoretical background required for a fundamental understanding of mnaway reactions and reviews the thermodynamic and kinetic aspects of chemical reactions. An important part of Chapter 2 is dedicated to the heat balance of reactors. In Chapter 3, a systematic evaluation procedure developed for the evaluation of thermal risks is presented. Since such evaluations are based on data, Chapter 4 is devoted to the most common calorimetric methods used in safety laboratories. 

Level 1 Chemistry and Thermodynamics. This level deals with the analysis of the fundamental knowledge needed for performing the conceptual process design. A detailed description of chemistry is essential for designing the chemical reactor, as well as for handling safety and environmental issues. Here, the constraints set by chemical equilibrium or by chemical kinetics are identified. The nonideal behavior of key mixtures is analyzed in view of separation, namely by distillation. 

The tiiermal behaviour of a chemical reactor depends on the thermodynamics of the process, on the reaction rate, vtdiich has already been mentioned above, but also on the mode of exchange with the environment. This is completely described in the overall heat balance of the system. The following sections will present the main balance equations, which are required for the subsequent safety assessment, as well as definitions and interpretation of characteristic numbers used in their presentatioiL... 

The expediency of using eutectic lead-bismudi alloy as primary circuit coolant in nuclear reactors is due to its physical and chemical and thermodynamical characteristics which enable to meet the safety requirements the most completely. 

Chapter 22 "Heat Transfer, Thermal Hydraulic, and Safety Analysis" and Chapter 23 "Thermodynamics and Power Cycles" are analytical tools used by engineers to evaluate reactor and power-producing systems. Heat transfer and thermal hydraulics are not only important in the operation of nuclear reactors, they are also critical in the evaluation of how the systems will respond under upset conditions. The chapter on thermodynamics is included to show how the energy generated by the reactor is transferred by the reactor cooling system to the turbine power generating system used to produce electricity. 

Future Trends in Reactor Technology The technical reactors introduced here so far are those used today in common industrial processes. Of course, research and development activities in past decades have led to new reactor concepts that may have advantages with respect to process intensification, higher selectivities, and safety and environmental aspects. Such novel developments in catalytic reactor technology are, for example, monolithic reactors for multiphase reactions, microreactors to improve mass and heat transfer, membrane reactors to overcome thermodynamic and kinetic constraints, or multifunctional reactors combining a chemical reaction with heat transfer or with the separation in one instead of two units. It is beyond the scope of this textbook to cover all the details of these new fascinating reactor concepts, but for those who are interested in a brief outline we summarize important aspects in Section 4.10.8. 

Passive safety systems based on natural circulation are intended to provide the ultimate heat sink in cases of failure of the normal operation of the reactor cooling system. Because of its critical importance, fundamental understanding of the properties and characteristics of namral-circulation hydrodynamics, thermal responses, and thermodynamics in the complex engineering equipment of nuclear reactor power systems is essential. For the Gen IV systems that are based on natural circulation at normal operating states the properties and characteristics under steady-state conditions must also be well understood. 

The basic data - the chemistry and the thermodynamics for the process - will define limits for a broad range of conditions at which the reaction is possible. The kinetics of the reaction and the properties of the catalyst, especially its thermal stability, will further narrow the range of possible reaction conditions and define a window of possible operating parameters. Process optimization, energy efficiency, and safety aspects will then determine at what conditions within the window the reactor should operate to give the optimum result. And then mathematical models are used to determine how big the reactor must be to obtain the performance (conversion and pressure drop) determined by the process optimization. 

TAEA participated to the OECD/NEA International Standard Problem No 42 (ISP-42) which is hosted by the Paul Scherrer Institut (PSI), Switzerland. The ISP-42 test was performed in the PANDA test facility, at the PSI, as a sequence of Phases A through F, representing typical passive safety system operating modes covering certain specific phenomena. The configuration used for ISP-42 was corresponding to the European Simplified Boiling Water Reactor containment and passive decay heat removal system at about 1 40 volumetric and power scale, and full scale for time and thermodynamic state. 

The NOKO test facility located at the Institute for Safety Research and Reactor Technology of the Research Center Julich is a thermal hydraulic test rig, which was constructed within the framework of a research task in a joint project of the Research Center Julich (FZJ) and SIEMENS AG, Power Generation Division (KWU), with support from the German Federal Ministry of Education, Science, Research and Technology and German utilities. The facility is suited for a broad spectrum of experiments in the field of thermodynamics and fluid dynamics of water, water vapor and non-condensable gases. Different passive safety systems can be investigated with only minor modifications. 

---