Zone 2 Ventilation System

In the MER, a separate fan exhausts 400 cfm from the Zone 1 Filter Room and discharges it into the ventilation exhaust. The purpose of this system is to exhaust any airborne contamination that could result from Zone 1 ventilation system filter replacements or fan maintenance to the HCF stack. 

In all of the SCB fire scenarios, the fire was assumed to envelop the liquid dissolution cocktail in the process containers during or following UO2 dissolution and release of radioactive material to the SCB and Zone 1 ventilation systems. While dilution of combustion products is expected to preclude damage to the ventilation system, an unmitigated release bounds the scenario where the filters or the ventilation system itself have been degraded or compromised as a consequence of a fire. The frequencies per year for such an accident developed in the event tree analysis shown in Appendix 3E.3 agree with the frequency for an extraction SCB fire as assessed in event CP-7 in the hazard evaluation (Appendix 3C). 

In addition, the SCBs are part of the Zone 1 ventilation system. Each SCB is operated independently of the other SCBs. Airborne leakage from each SCB to Zone 2 (the general work areas) is prevented by maintaining a nominal negative pressure differential of approximately 6.4 mm (0.25 in.) WG between each SCB and the Zone 2A canyon, with a similar pressure differential maintained between the Zone 2A canyon and Zone 2. SCB manipulators, which penetrate both the SCBs and the Zone 2A canyon, are sealed with a manipulator boot. More detailed descriptions of the SCBs can be found in Chapter 2. 

Zone 1 Ventilation System SSSSC Ventilation supply and exhaust ductwork connected to each SCB. 

Local ventilation systems are used for local controlled zones. These systems are based on local capture of contaminants. 

Local ventilation systems (see Fig. 2.2) are used for local controlled zones. These systems are air technological methods for local protection. Primarily, local protection should be made using process methods such as encapsulation or process modification (see Design Methodology, Chapter 3). Another use for local ventilation systems is source capturing. 

Shilkrot, E. O. 1993. Determination of design loads on room heating and ventilation systems using the method of zone-by-zone balances. ASHRAE Transactions, vol. 99, no. 1. 

The use of a natural ventilation system assumes temperature stratification throughout the room height. Air close to heat sources is heated and rises as a thermal plume (Fig. 7.105). Part of this heated air is evacuated through air outlets in the upper zone, and part of it remains in the upper zone, in the so-called heat cushion. The separation level between the upper and lower zones is defined in terms of the equality of and G, which are the airflow rate in thermal plumes above heat sources and the airflow supplied to the occupied zone, respectively. It is assumed that the air temperature in the lower zone is equal to that in the occupied zone, and that the air temperature in the upper zone is equal to that of the evacuated air,... 

Another factor influencing contaminant and heat transfer from dirty to clean zones against the stable airflow is a turbulent exchange between these zones. This process should be considered in the design of displacement or natural ventilation systems and evaluation of the emission rate of contaminants from the encapsulated process equipment (Fig. 7.111a). 

The mechanism of turbulent heat exchange between tbe upper and lower zones in the case of ventilation system design with temperature stratification is described in Section 7.3. 

The demands and design of a local ventilation system (not only local ex hausts) should naturally start with the demanded target levels and the toxicity of the air contaminants (see Chapters 5 and 6). For best performance the exhaust should be close to the source and preferably enclose the source, there should be no disturbances of the flow, and at the same time it should have a low flow rate and be able to minimize the concentration of even quite dangerous air contaminants in the working zone. 

The study shows, however, that the air curtain in the original design is bent off the wall due to the presence of the open oven with induced airflow inside the oven. This unexpected flow feature finally leads to a recirculation zone below the oven, and dust particles on the floor can be carried into the oven (class B quality). This effect was then also confirmed by smoke experiments in the real room and the existing ventilation system. 

Clean air and many air contaminants are under normal conditions invisible. It is, however, often desired to actually see the movement of air or the emission and transport of contaminants in order to ensure good air quality.. Methods aimed at the visualization of airflow, contaminants emission to the air, and their transportation out in the workplace and to the breathing zone of the worker are therefore important tools for designers of industrial ventilation systems. 

Red zone The primary air containment zone in ventilating systems in the atomic energy industry. ... 

Local extract is used to remove contaminants directly from a process to the exterior without passing through personnel breathing zones. It thus provides a high degree of safety and because small volumes of air are extracted relative to a dilution ventilation system it is energy efficient. 

Ventilation is the standard method of controlling exposure to airborne vapors of epoxy resins and solvents. Ventilation involves controlling air flow to reduce exposure. Local exhaust ventilation systems capture the vapor at the source and either filter or remove it from the work area. The ventilation system needs to be designed so that vapors, aerosol, and dusts are pulled away from, and not into, the breathing zone of the workers. A constant supply of fresh, noncontaminated air should be available at all times. 

The ventilation system of the premises must be independent and designate so that no contamination of the environment is possible. This can only be achieved by combining the creation of zones of different pressures (positive or negative) with the installation of filters which protect both adjacent premises and the external environment. 

Divided into three zones of goaf spontaneous combustion working surface of W type and U type ventilation system... 

Since the ventilation system is shutdown automatically and the airinventoiy in the room is reduced by the division into four smaller zones, oxygen concentration in the combustion room and neighboring room is reduced. (See Fig. 15). 

Special attention has been also paid to fire fighting. It includes the partition of the plant in fire zones limited by fire-resistant walls. Each zone has its own ventilation subsystem able to isolate it from the neighboring zones. The ventilation system is designed to remove the fumes generated in the room impeding the access for the fire fighter crews and to maintain the room pressure in the damaged zone below that of the other zones. 

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