Condensate backup systems

Offgas treatment is extensive and involves use of sintered metal filters, quench systems, venturi scrubbers, a condenser, a mist eliminator, an offgas heater, parallel HEPA filters, a carbon filter for radioactive iodine removal, a baghouse, and a selective catalytic reduction unit a packed tower scrubber system is used as a backup. 

The service raw vfStet system serves as a backup water source to the high activity moderator condensers. The service raw water is tied to the river water and allows complete standby of BuUding i90-K.. ... 

By far the most (about 96 per cent) of the heat generated In the reactor is removed ffom the reactor by the primary coolant system, transferred to the boiling water secondary system and dissipated to the Columbia River via condenser cooling water streams, failure of the primary coolant system to remove heat from the reactorat design power level will result In certain fuel melting unless the last-ditch backup cooling system functions. 

Critical interlock While identifying the hazards it is important to categorize critical interlocks (for new plants, data/experience from similar plants may be helpful) for which sufficient backup may have to be arranged as a safety measure. In many of these cases, in addition to software interlock, hardware interlocks are also provided. In some cases, even mechanical protection is provided. A critical trip interlock pertinent to a turbine is an example. For turbine overspeed, condenser vacuum, etc., in addition to electronic interlock (with sufficient hardware/software redundancy), mechanical interlocks are provided so that the equipment is saved. Choke and kill in offshore is also an example of this. Regulations To meet the requirement of a regulatory board or company standards, measures are taken to enhance overall safety. Incorporation of these safety measures does not always mean that risk is adequately reduced. These measures could make the system acceptable for use, and a local regulatory board may require additional precautions. An example will elaborate the situation. Many turbine manufacturers give low forward power relays or reverse power... 

The APIOOO does not need a containment spray system to cool the containment atmosphere, because this function is performed by the passive containment cooling system. The principal means of post-accident isotope control for the APIOOO relies on natural forces, like natural convection, condensation and conduction, to transfer decay heat from the lower regions of the containment to the containment walls, which are cooled (there is also a containment spray utilising the fire protection system (see Section 8.4.3.10), as a backup for this function. The resulting steam condenses onto the containment wall, and then returns to IRWST or to the containment sump by gravity. Through analysis and testing, it has been shown that the soluble and suspended isotopes move with the water, and thus finish up in the water in the IRWST or the lower portions of the containment. 

Pressure in the primary coolant system is maintained by the on-line, boiling-water pressurizer. Water temperature, and hence steam pressure, is regulated by electric immersion heater batiks and by a spray of water from the cold leg of the primary coolant system A control bank of heaters will ordinarily operate continuoi sly and the sprays intermittently Larger capacity heaters and spray units are available as backups for control during the more severe transients A vent system Is provided to prevent accumulation of non-condensable gases which would adversely affect the ability to control pressures The pressurizer is hydraulically connected to the remainder of the primary coolant loop at the outlet manifold located in the 109-N Building Pipe Gallery ... 

---