Reactor hazard potential

Another reaction with hazardous potential is the synthesis of methyl isocyanate from mefhylformamide, which was investigated using a micro reactor in industry [74],... 

APPLICATION OF THE RADIOLOGICAL HAZARD POTENTIAL (RHP) TO RADIONUCLIDES IN MAGNOX REACTOR DECOMMISSIONING... 

Gasteiger, R., "Development of an Irradiation Technology for the Recycling of Am-2l+l in Nuclear Reactors — A Contribution to the Possibilities for the Reduction of the Hazard Potential of a-Bearing Wastes," (in German), KFK-21+31 Nuclear Research Center, Karlsruhe, Federal Republic of Germany (1977). 

Using the design postulated above the hazard of a fusion reactor can be estimated. Fusion reactors will present only a tiny fraction of the radiation hazard potential of a uranium fission reactor. There is only a small quantity of radioactive tritium present in the reactor. Based on the tritium usage in research reactors it would seem likely a power reactor would have less than a few kilograms of tritium at the power plant at any given time. This would probably be distributed 10% to 20% in the plasma, 20% to 40% ready for future insertion in the plasma and the un-recovered tritium present in the lithium coolant. 

An example for the safe production of toxic materials in a microsystem was given by Ajmera et al. [40]. A micropacked-bed reactor made from silicon was used for phosgene synthesis to demonstrate the reactor s potential for safe on-site and on-demand production of a hazardous compound. 

Independent of the mode of reactor operation it is of tremendous importance to stop any further addition of fijesh reactants to the system, once a maloperation has occurred. This should be ensured technically, whenever possible. In elderly plants, organizational measures can be sufficient, provided they are of very good quality. The interruption in supplies eitsures that the hazard potential related to the maloperation remains restricted to the substance amoimt present in the reactor at the time of process disturbance. All further elaborations assume this effective interruption in supplies. 

The potential for chemical reactions adding to the hazards following a reactor accident requires serious assessment. The safety systems of reactors need to be designed to ensure that the probability of temperatures leading to dangerous levels of chemical reaction is extremely low. In the selection of materials for reactor components, potential chemical reactions should receive special attention. 

The guidance given in this publication is applicable to research reactors with limited hazard potential to the public and typical characteristics. For addressing the topic in research reactors with several tens of megawatts of power, fast neutron spectrum research reactors or small prototype power reactors, etc., other similar IAEA publications prepared for power reactors may be more appropriate for a number of aspects (see References). No specifications for such a transition to other guidance are presented. 

Methods, procedures, and check lists for process operations with nuclear hazard potential eu e prepcured to ensure that execution of maintenance work, process functions, inspections, functional tests of critical equipment, reactor startup preparations, and reactor operations are conducted In accordance with Process Standards and Equipment Maintenance Standards. Special operating and maintenance procedures are provided for in-reactor test facilities. 

Polymerization processes are carried out in many different variations. Process selection depends on the monomer and, also, strongly on the desired product properties. Selection of the right polymerization process is also very important with regard to process safety. Polymerization reactions belong to the most dangerous processes in the chemical industry with respect to the risk of an uncontrollable thermal runaway in the reactor. The reasons for the special hazard potential caused by polymerization reactions are threefold ... 

The commissioners discussed the WASH-740 report at a meeting on 20 March when they took up their prepared draft testimony on the Price-Anderson bills. Harold Price commented that the report provided an assessment "insofar as practicable" of the potential hazards. Libby, the most knowledgeable commissioner on reactor hazards, remarked that the study was the best that could be prepared at the time. He suggested,... 

Clearly, the potential hazard from runaway reactions is reduced by reducing the inventory of material in the reactor. Batch operation requires a larger inventory than the corresponding continuous reactor. Thus there may be a safety incentive to change from batch to continuous operation. Alternatively, the batch operation can be... 

Potential fusion appHcations other than electricity production have received some study. For example, radiation and high temperature heat from a fusion reactor could be used to produce hydrogen by the electrolysis or radiolysis of water, which could be employed in the synthesis of portable chemical fuels for transportation or industrial use. The transmutation of radioactive actinide wastes from fission reactors may also be feasible. This idea would utilize the neutrons from a fusion reactor to convert hazardous isotopes into more benign and easier-to-handle species. The practicaUty of these concepts requires further analysis. 

Once a decision to use QRA has been made, you must decide whether frequency and/or consequence information is required (Steps 6 and 7). In some cases you may simply need frequency information to make your decision. For example, suppose you wish to evaluate the adequacy of operating procedures and safety systems associated with a chemical reactor. The main hazard of concern is that the reactor could experience a violent runaway exothermic reaction. You believe that you know enough about the severe consequences of a runaway and nothing more will be gained by quantifying the consequences of potential run-... 

Impurities or the delayed addition of a catalyst causes inhibition or delayed initiation resulting in accumulation in the reactors. The major hazard from accumulation of the reactants is due to a potentially rapid reaction and consequent high heat output that occurs when the reaction finally starts. If the heat output is greater than the cooling capacity of the plant, the reaction will run away. The reaction might commence if an agitator is restarted after it has stopped, a catalyst is added suddenly, or because the desired reaction is slow to start. 

A first attempt to estimate the potential consequences from severe LWRs accidents was the BNL report WASH-740 (1957). The authors of WASH-740, to overcome the lack of information and methods, estimated "Hazard States based on the core state, radioactive inventory, fuel cladding, reactor coolant system, and containment conditions. 

Interactions refers to any jobs, tasks, or operations carried out by people who could directly or indirectly cause the hazard to be released. Direct interactions with the plant might involve breaking open pipework, opening reactors, etc. Indirect interactions would include remote activation of valves from a control room, or the performance of maintenance on critical plant items. Errors that might occur during these interactions could allow the harm potential to be released. This could occur directly (for example, a worker could be overcome by a chlorine release if an incorrect valve line-up was made) or indirectly (for example, if a pump bearing in a critical cooling circuit was not lubricated, as in the example in Chapter 1). The procedure as described above... 

Clearly, the potential hazard from runaway reactions is reduced by reducing the inventory of material in the reactor. 

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