Design-basis accidents

It would be quite appropriate to draw here an analogy with the generally accepted approach to safety assessment of nuclear power plants where, along with the probabilistic safety analysis, each NPP is calculated for the maximum possible (i.e. beyond the design basis) accident in order to obtain as conservative assessment as possible. 

Barskov, M.K., Smirnov, P.L., Gavrilov, S.D., et al. (2002) Storage and transportation of naval spent nuclear fuel engineering solutions and radiation consequences of beyond-the-design-basis accidents, J. 

List of the design basis accidents is given in Table 7. 

TABLE 8.List of Beyond the Design-Basis Accidents... 

Calculation results of radiation factors analysis show that maximum annual effective radiation dose for population in case of the design-basis accident during Victor II dismantling will not exceed 0.1 mSv. It is considerably less than dose limit for population under normal operational conditions given in Radiation Safety Standards (NRB -99). 

Electric wires and cables used in nuclear power plant are exposed by low dose rate irradiation during the life time of the plant. In addition, loss of coolant accident (LOCA) that is a design basis accident brings about the degradation by heat and radiation on the electric wire and cables. The dose varies from plant to plant. IEEE std.323-1974 (/) estimated the dose 0.5 MGy for the period of the life time and 1.5 MGy for LOCA as one of the example. The standard estimated 40years and one year, for the lifetime of plant and duration of LOCA respectively. 

Some results from a safety analysis for the French liquefaction plant near Lille with an LH2 production rate of 10 t/d have been reported showing that in a design basis accident represented by an LH2 pipe rupture, the maximum escape rate is 1.9 kg/s. Assuming a wind velocity of 2 m/s, a hydrogen-air mixture cloud will evolve with a predicted maximum extension of approx. 200 m within the flammability limits. A safety distance of 238 m around the LH2 facilities for the plant was considered sufficient to protect offsite residential areas [5]. 

CEFR is pool-type reactor and the main vessel is divided into two parts. The upper part is called hot pool because it contains hot sodium whose temperature is 516 centigrade degree. The lower part is called cool pool because it contains cool sodium whose temperature is 360 centigrade degree. This accident is a BDBA (Beyond Design Basis Accident) in the Primary Safe Analysis Report of CEFR. Here are initial conditions,... 

At beyond design basis accidents 20rem 0,5 rem (on SPZ boundary)... 

Primary coolant components are placed inside the safeguard vessel and imder all designbasis accidents the possible release of radionuclides would be retained within the safeguard vessel. Only under beyond design-basis accidents when pressure exceeds the allowable limits the radioactive medium could be released from the safeguard vessel into the containment through the bubbling device. 

Under the accidents caused by primary coolant leak this gap is filled witii water thereby providing adequate heat removal from the reactor vessel. That excludes the probability of reactor vessel meltdown under postulated beyond design-basis accidents involving the core dryout. 

The function of the ROPS is to reduce the reactor pressure at the postulated beyond design basis accident related with a control system failure. The system consists of two parallel trains which are connected to the PZR through a single pipeline. Two trains are also combined to a single pipeline connected to the internal shielding tank. Each train is equipped with... 

Beyond-Design-Basis Accident Avoids Radionuclide Release By Decay Heat Conduction To Ground... 

Accidents that will probably not occur during the life cycle of the facility. This class includes the design basis accidents. Frequency between 1 in 10,000 y and once in 1,000,000 y ... 

Facilities for the removal and storage of heavily contaminated clothing and equipment, the personal decontamination of operators, the availability of hot showers, provision of clean clothing and radiological dose supervision also appeared to be less than adequate for a major incident. Lessons can be learned from the Chernobyl accident in this respect and facilities and procedures provided to suit the worst situation resulting from a design basis accident. However, it is difficult to suggest how accident conditions can be portrayed more realistically. 

In the field of nuclear engineering this is referred to as design basis accident . 

In nuclear installations the so-called design basis accidents are used for this purpose [19]. For example, the complete failure of the main coolant pipe of a reactor ( 2-F — rupture because the entire cross section is open on both sides) or the failure of the electric supply [19]. The design basis accidents serve to determine the type and dimensions (e.g. capacity, temperatures, cooling power...) of the corresponding safety systems, for example the emergency cooling system for counteracting the breach of the main coolant pipe. 

SSCs which are relied on to remain functional following a design basis accident to ensure the continued performance of safety functions, or whose failure could prevent safety related SSCs from performing their safety related functions ... 

SSCs which are used in plant emergency operating procedures (EOPs) or are relied on to mitigate the consequences of transients or beyond design basis accidents. 

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