Reactor safety basics

Safety first has always been and continues to be the basic policy of the nuclear industry. This includes reactor safety by design as well as activities to discourage the proliferation of nuclear weapons and to prevent sabotage of nuclear facilities. This policy has been successful the chance of death from a nuclear accident is over a million times less than death... 

Nuclear Submarines with Damaged Reactor Installations Basic Engineering Solutions and Safety-Related Problems... 

The notion that methods of statistical analysis should be applied to reactor safety standards was first put forward by Siddall of Atomic Energy of Canada Ltd., Chalk River, Ontario in 1959 (57). This early paper is of interest because it invokes the notion of a balance between increased wealth of the community that may be expected to accrue from the advent of nuclear power on the credit side, and risks of injuries and deaths because of the hazards of the nuclear process on the other it goes on to suggest money costs (economic criteria) as the avenue through which to achieve such a balance. The details given in the paper are only generally relevant today, but some of the introductory sentences have a modern sound to them and are worth quoting as an introduction to the basic philosophy of the probability approach to reactor safety. The study of nuclear-reactor safety (i.e., in 1959, some 15 years ago in the life of an industry now only 20 years of age) is in an unsatisfactory state. Some aspects of the problem have received... 

Preparation of a proposal for the project Partnership for Basic Research and Education in Nuclear Reactor Safety and Novel Applications of Transport Theory. This proposal was submitted to, and ultimately accepted by, the International Science and Technology Center. KIAM was the lead organization for this project, with Professor Mikhail V. Maslennikov as Project Manager, and Dr. A. V. Voronkov as the Project Leader at KIAM, and Professor Nelson as Principal Consultant. Other participating Russian organizations were... 

Reactor Instrumentation categorizes Itself Into three basic classifications. Hie first division can be defined as Reactor Safety Circuit Instrumentation. Instruments In this classification provide Information on the status of the process by visual readout devices auid are connected directly Into the reactor safety circuits for automatic shutdown If preset limits are exceeded. They are responsible for maintaining the stemdards of reactor and nuclear safety at all times. The second category Is Reactor Procet... 

Reactors Obese two sheets cover basically the entire reactor safety instrumentation power supply and safety clrciiit system program concept. The following discussion will reference these sheets. 

In the Operational Safety research activities of the Community, up to now and especially under FP-4 the emphasis was put on the T component, i.e. the identification and solution of technological problems. Traditionally the technological problems of nuclear reactor safety are related to the 3 basic safety functions, namely controlling the power, cooling the fuel and confining the radioactive material. Their solution lies in the standard 3-levels defence-indepth approach against accidental radioactivity releases, i.e. ... 

The basic safety philosophy of nuclear plant design and operation is that the design should be conservative, there should be ample safety margins in operation, and redundant and diverse components and systems should be provided to cover the unknown imcertainties. A concept called defense-in-depth is used in developing reactor safety. 

Zone II requirements are recommended for buildings not critical to reactor safety and a basic horizontal ground acceleration of 0 1 g for non-critical structures buildings, components, etc, which are not specifically defined by the building code ... 

The basic propositions of the Package-Reactor safety concept are as follows ... 

The approach is oriented to the recommendations made by the Reactor Safety Commission and takes into consideration the basic requirements of the Atomic Energy Act, the safety criteria defined by the Federal Ministry of the Interior, and the Reactor Safety Commission guidelines for pressurized and boiling water reactors (Fig. 2). As mentioned before, these requirements are to be integrated into the KTA 2000 standard. 

Lamarsh, J. R. and A. J. Baratta. 2001. Introduction to Nuclear Engineering, 3rd ed. Upper Saddle River, NJ Prentice Hall. This book, now in its third edition, was originally based on the class notes and lectures of the late Dr. John R. Lamarsh. It contains an overview of the field of nuclear engineering and discusses the basics of atomic and nuclear physics, nuclear reactor theory, and reactor design, and both U.S. and non-U.S. nuclear reactor design. Information on nuclear reactor safety is also included. References and practice exercises are included at the end of most chapters. 

This Safety Guide was developed under the IAEA programme for safety standards for research reactors, which covers all the important areas of research reactor safety. It supplements and elaborates upon the Safety Requirements publication on Safety of Research Reactors [1] by presenting recommendations on the best practices, based on international experience, to meet the safety requirements of Ret [1] and those of the International Basic Safety Standards for Protection against Ionizing Radiation and for the Safety of Radiation Sources [2]. 

In Germany the conceptual design phase for a BWR which includes extensive use of passive safety features has been completed and the basic design phase (scheduled for 4 years duration) has just started in co-operation with interested German utilities. The concept has already been discussed with the German Reactor Safety Commission (RSK). A number of European countries expressed their interest in being involved in the design activities of the new BWR concept. 

Reactor criticality is attained and maintained with cadmium-sheet safety, shim, and control rods that move vertically along the outer side of the 36-in.-diameter tank. Primary features for reactor safety are the quick dump system for the water moderator, and the availability for sudden insertion of 3 cocked safety rods (similar to the control rods), plus the control rods. Further details of the reactor design and safety aspects are discussed in Appendix B. About 24 reactors basically similar to the Argonaut have been or are being constructed in various parts of the world. 

Our present discussions relate only to the laboratory testing of safety-related secondary systems, as are employed in critical areas such as areas of emergency power supply and reactor power control supply etc. of a nuclear power plant (NPP) according to IEEE 344 and lEC 60980. There are other codes also but IEEE 344 is referred to more commonly. Basically, all such codes are meant for an NPP but they can be applied to other critical applications or installations that are prone to earthquakes. 

The achievement of an economic optimum is limited by requirements of selectivity, energy efficiency, safety, and pollution control. The total design of production reactors therefore involves a few more tasks than the basic integration method. 

The basic requirements of a reactor are 1) fissionable material in a geometry that inhibits the escape of neutrons, 2) a high likelihood that neutron capture causes fission, 3) control of the neutron production to prevent a runaway reaction, and 4) removal of the heat generated in operation and after shutdown. The inability to completely turnoff the heat evolution when the chain reaction stops is a safety problem that distinguishes a nuclear reactor from a fossil-fuel burning power plant. 

Containment design details - basic structure, major contents (beat structures), internal safety systems performance data, special features, reactor cavity/sump details, layout elevations and floor plans, fnateriais specifications, design limits, etc. 

The analysis of transient flows is necessary for safety analysis of nuclear reactors. Such efforts usually result in the development of large computer codes (e.g., RELAP-5, RETRAN, COBRA, TRAC). Rather than going into the details of such codes, this section gives the principles and basic models involved in the analysis. 

Scale-up can also have a significant effect on the basic process control system and safety systems in a reactive process. In particular, a larger process will likely require more temperature sensors at different locations in the process to be able to rapidly detect the onset of out-of-control situations. Consideration should be given to the impact of higher-temperature gradients in plant-scale equipment compared to a laboratory or pilot plant reactor (Hendershot 2002). 

AECL has evaluated some of the basic information and development requirements in some detail (24, 25) and has outlined the type of fuel recycle development program which would be required. It would involve research and development of thorium fuels and fuel fabrication methods, reprocessing, demonstration of fuel management techniques and physics characteristics in existing CANDU reactors and demonstration of technology in health, safety, environmental, security and economics aspects of fuel recycle. 

In addition to the importance of combustion reactors in chemical processes, mcon-troUed combustion reactions create the greatest potential safety hazard in the chemical industry. Therefore, all chemical engineers need to understand the basic principles of combustion reactors to recognize the need for their proper management and to see how improper management of combustion can cause unacceptable disasters. 

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