Process and installation to secure a prestressed concrete pressure vessel surrounded by a reactor protection building against excessive pressure and to prevent the release of activity to the environment

An apparatus for securing against excessive pressure in a prestressed concrete pressure vessel surrounded by a reactor protection building in a nuclear reactor installation, wherein within the prestressed concrete pressure vessel is a gas cooled high temperature reactor equipped with a primary cooling loop at least one means for steam generation and steam blower means associated therewith, comprising:

• an air circulation installation within the reactor portection building and connected to an exhaust stack outside the reactor protection building by a filter means for prevention of release of activities to the environment;
• a first means for release of pressure within said pressure vessel when the pressure rises in said pressure vessel made up of means for operational cooling gas purification connected to the prestressed concrete pressure vessel, a first blower means for conveying cooling gas connected to said means for operational gas purification and vessel means for storage for cooling gas connected to said first blower means;
• a second means for release of pressure within said pressure vessel when pressure reaches a first predetermined level, wherein said second means operates to bypass said means for operational cooling gas purification and is made up of at least one secondary discharge path each made up of a normally closed safety valve connected to said pressure vessel and automatically activated when said first predetermined level is reach, and a check valve connected between said safety valve and said vessel means, wherein said safety valve and said check valve make up the secondary discharge path;
• and
• a third means for release of pressure within said pressure vessel when pressure reaches a second predetermined level, wherein said second predetermined level is higher than said first predetermined level, made up of a normally closed rupture disk means for opening at said second predetermined level connected in a discharge line, wherein said discharge line is connected at a first end to said secondary discharge path between said safety valve and said check valve and at a second end to said air circulation installation wherein said check valve operates to prevent the emptying of cooling gas from said vessel means.