Example of a category 4 accident main steam line break

Example of a category 4 accident main steam line break 

In this scenario, it is assumed that one of the outlet lines of a steam generator suddenly breaks. The concept of leak before break , which excludes the guillotine break of the large primary lines, cannot be applied to the steam lines because it is difficult to demonstrate that a steam leakage from a quasi-critical crack can be detected in time with certainty. This accident, therefore, has to be considered less unlikely than a primary pipe break. 

According to the position of the rupture, to the initial reactor conditions and to the accompanying malfunctions assumed, a variety of accidents with different consequences arise. 

In general, however, the rapid voiding of the affected generator causes  

The accident is analysed for various locations of the steam line break (an5rwhere along its length, for example before or after the isolation valve/s, inside or outside the container, etc.). Various initial operating conditions (full power or hot shutdown), as well as various additional malfunctions (loss of the external power supplies, highest worth control rod fully extracted, etc.) are possible. Some of these situations, in fact, are the worst for potential fuel damage, others for the primary over-pressure or for external radiological consequences. 

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