Failure of Containment

Some important parameters relating to the loss of containment are the following  

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Catastrophic failure of containers as cryogen evaporates to cause pressure build-up within the vessel beyond its safe working pressure (e.g. pressures <280 000 kPa or 40 600 psi can develop when liquid nitrogen is heated to ambient temperature in a confined space). 

Accidents may be caused by impact, failure of container or pipeline, or during loading/unloading. The hazards arise from ... 

Catastrophic failure of containers as cryogen evaporates to cause pressure build-up... 

Shipping containers such as drums and pails are subject to corrosion damage and failure when corrosive materials are shipped. Usually, internal corrosion is not a problem when the goods are shipped by the manufacturer as proper container material is used when the containers are transported in a short time. Corrosion can be a problem and result in failure when the contents are stored beyond the material s shelf life. The corrosion failure of containers with hazardous waste is a serious problem. This problem oceurs when wastes are mixed or when they are contaminated and stored in noncompatible materials. 

Spill of radioactive liquid materials Spill of radioactive resin or other debris <55 gallons per drum -Forklift puncture -Toppling of container (mishandling, energetic external event) -Fatigue failure of container Liquid radioactive material containers require mounting on spill pallets to control leaks and spills. 

S.4.2 Release of radionuclides in the event of a failure of containment isolation... 

Due to the failure of containment isolation during the first hours after the onset of the accident, large volumes of water containing high concentrations of fission products were transported to the auxiliary building, where large areas were overflooded. Here, a new iodine partition equilibrium was established with about 3%... 

Freight containers - failure of container or load bearing parts while it is being raised, lowered or suspended. 

Late containment failure is defined as eontainment failure postulated to occur later than 24 hours after the onset of core damage. Sinee the probabilistic risk assessment assumes the dynamic phenomena, such as hydrogen combustion, to occur before 24 hours, this feilure mode occurs only from the loss of containment heat removal via failure of the passive containment cooling system. The fission products that are airborne at the time of containment failure will be discharged at high pressure to the environment, as the containment blows down. Subsequent release of fission products can then pass directly to the environment. Accident sequences with failure of containment heat removal are grouped in release category CFL. 

On this basis, acute risk is considered with regard to mitigation of reasonably foreseeable (credible) containment failure events that could occur during the operational lifecycle of the facility. The possible acute accident scenarios for radioactive pollutants involve some form of failure of containment of vessels or pipework within the nuclear island or radwaste buildings. This approach is in general accordance with the assessment process required with regard to pollution by non-radioactive substances under EP. These accident scenarios are identified and analysed in Chapter 5 of the PCSR and are not discussed further in this section. 

Table 12.8. Radionuclide Atmospheric Release Fractions for PWR Core Melt Followed by Failure of Radioactivity Removal Systems and Failure of Containment Due to Overpressure"...

Late (> 2 Hours After Vessel Breach) Failure of Containment Heat Removal I Combustion 1 Non-condensible gas generation 1 Basemat Meltthrough ... 

Generation of pressures and shock waves that can fail vessel support structures, leading to movement of the vessel and failure of containment piping penetrations,... 

Given conditions leading to core melting, the possibility of early failure of containment or associated safety features cannot be precluded. 

This mechanism to form HI is an interesting process that could occur late in reactor accident sequences after zirconium oxidation is nearly complete and would likely affect the predicted source term after failure of containment. 

Failure of containment cooling--0% Failure of CCWS or Failure of heat removal station blackout 8% from secondary system 13% ... 

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