Safety management

Conservative analysis demonstrates how the design of the OPAL reactor meets design safety and licensing requirements.

 
Quantitative analysis of the reactor is performed with computer programs, in which parameters in the reactor core are studied, such as:

• Temperature of the fuel cladding and the coolant
• Flow rate through the core and flap valves
• Temperature of the pool and
• Reactor power.

A probabilistic safety analysis has also been performed as part of the overall safety analysis to demonstrate compliance with licensing requirements. This probabilistic safety analysis was completed in parallel with, but independent of, the deterministic safety analysis (the Safety Analysis Report).

The safety analysis also considers the consequences of very unlikely Beyond Design Basis Accidents, where it is assumed that a number of safety systems fail.

The hypothetical scenarios considered are as follows:

1. Primary cooling system pump shaft seizure with failure of the first shutdown system
2. Reactor and service pool cooling system pump shaft seizure with failure to detect the loss of flow
3. Partial blockage of cooling channels in a fuel assembly
4. Erroneous early removal of a Uranium-Molybdenum rig into the transfer hot cell
5. Control bank withdrawal at nominal velocity during start-up
6. Control plate withdrawal during start-up to low power operation with failure of the first shutdown system and success of the second shutdown system
7. Total plant blackout for 10 days

The analysis show that for all design requirements, the reactor goes through a series of safe states, with no damage to the core or the rigs.

Key results of the safety analysis are as follows:

• The core is capable of being cooled by natural circulation without operator intervention for more than 10 days before requiring coolant make-up.
• The reactor is capable of coping with a full break in the 350 mm primary cooling system line.
• The passive siphon effect breakers ensure the cessation of any pipework leak.
• The reactor can cope with severe losses of flow in the primary cooling system and reactor and service pool cooling system with no damage to either the fuel or the rigs.
• Reactivity insertion transients are moderate and self limiting.
• Failure of the Cold Neutron Source does not challenge the safety of the core.
• The reactor can cope with the continuous extraction of a control plate during reactor start-up with failure of the First Shutdown System.
• Losses of heat sink lead to benign transients with no adverse impact on the core or rigs.
• The design is resistant to human-induced errors.