All accidents initiated by equipment failure occur in the intact heat transport system. Therefore, the following issues are relevant to this family of accidents:
Some accidents in this group are subject to only one of the above issues, e.g. a pump power seizure concerns only the issue of the power-cooling mismatch in the channels. Other accidents encounter several above issues simultaneously, e.g. a loss of AC power supply encounter a loss of circulation as well as pressurization. The equipment failure accidents addressed in SAR are as follows:
However, in accordance with regulatory requirements  the following accidents initiated by equipment failure should be also analyzed:
Consequences of all the accidents initiated by equipment failure are explored by three cases that are simulated explicitly: MCP seizure, loss of AC power and loss of feedwater supply. The remaining accidents are assessed qualitatively. It is explained how these latter cases relate to the simulated cases, or it is shown that adequate provisions are available in the current plant to make the accident benign.
For the pump failure cases the automatic power reduction is the only required mitigation action. Analysis of the most severe conceivable power-cooling mismatch shows that cladding dry-out is avoided. A combination of a timely power trip, a pump costdown, and relatively early ECCS water injection maintains the cladding and pressure tube wall temperatures below their initial values for accidents that involve a global impairment of forced circulation, i.e. a loss of AC power and a loss of feedwater supply. There is no potential for power-cooling mismatch in accidents that maintain forced circulation, e.g. turbine trip and loss of main heat sink. The accidents that lead to an impairment of steam removal from the heat transport system, i.e. loss of AC power, loss of turbines and loss of heat sink, activate the MCC over-pressure protection system. The SAR analysis shows that this system is adequate, if the timely power reduction is given.
The SAR analysis shows that the reactor power is reduced in a timely manner in all accidents initiated by equipment
failures. Either power setbacks AZ-3 or AZ-4, or a trip AZ-1 are performed by the CPS on signals by the EPPS. There are at least two EPPS signals issued in close succession, based on diverse process parameters. Hence, reliable signals are available to activate the reactor power reduction.
The short-term ECCS is not activated in any accidents initiated by equipment failures because there is no break in the MCC to produce the necessary conditioning signal of high pressure in one of reinforced leak-tight compartments. However, the long-term emergency core cooling function is activated quite early in accidents that involve an impairment of steam removal or feedwater supply. The long term emergency feed water supply is preferentially provided by the AFWPs drawing hot water from the deaerators. If AFWPs cannot provide this emergency supply, the ECCS pumps, already running in a re-circulation mode, supply “cold” water from the condensate chambers in the ACS. No automatic system is available to regulate the emergency water supply in the long term, and to establish a long-term heat sink for the removal of decay and stored heat. These functions are performed by operators. Analysis shows, that adequate time is available to initiate the manual operator actions.
Thus, results of analysis show, that the class of events included under accidents initiated by equipment failures are unlikely to cause power plant conditions that would result in violation of the design criteria to avoid fuel damage, maintain integrity of pressure boundaries, and not exceeded regulatory dose limits. The existing protective system at the Ignalina NPP are adequate to bring the plant into a safe state following all accidents initiated by equipment failures.