Pressure suppression chamber

The pressure-suppression type primary containment is a cylindrical concrete structure with an embedded steel liner type with two major compartments a drywell and wetwell. The lower part of wetwell volume is filled with water that works as the condensation pool, and the upper part is a gas compression chamber. The blow-down pipes from the safety relief valves are routed to the pressure suppression pool. 

The pressure suppression function is supported by a four train containment spray system that is continuously in service, with one train supplying spray water from the condensation pool to the gas compression chamber in accident situations the system will start operation at full capacity. Spraying is also possible for the upper drywell - after rerouting, on operator action. The drywell spray is generally initiated only in the event of "small" LOG As to "depressurize" the containment. 

A containment is provided that completely encloses the reactor systems, drywell, and suppression chambers. The containment employs the pressure suppression concept. 

A pressure relief function is used to control large pressure transients. This system will operate safety/relief valves following closure of the main steam isolation valves or the sudden closure of the turbine admission or stop valves and failure of the turbine bypass system to relieve the excess pressure. For this fimction, the safety/relief valves discharge steam from the steam lines inside the drywell to the suppression chamber. Each safety/ relief valve is operated from its own overpressure signal for the relief fimction, and by direct spring action for the safety function. 

The steam which in a loss-of-coolant accident is released from the primary system may lead to a pressure increase inside the containment and to a pressure difference between the drywell and the condensation chamber. As a consequence, a steam-air mixture is transported to the pressure suppression pool where the steam is condensed. Simultaneously, fission products which might be carried with the steam are retained in the water volume of the pool, thus efficiently reducing airborne radioactivity. 

Energy management features are incorporated that limit the internal pressures and temperatures within the containment envelope to values that are below the design limits for the containment system and the equipment that is needed inside the containment when a design basis accident occurs. Examples of energy management features include pressure suppression pools, ice condensers, pressure-relief vacuum-chamber systems, structural heat sinks, the free volume of the containment envelope, spray systems, air coolers, a sump or a suppression pool recirculation water-cooUng system, and the air extraction system for the annulus in double-containment systems. 

Fig. 12.11 shows the structure of a rocket plume generated downstream of a rocket nozzle. The plume consists of a primary flame and a secondary flame.Fil The primary flame is generated by the exhaust combustion gas from the rocket motor without any effect of the ambient atmosphere. The primary flame is composed of oblique shock waves and expansion waves as a result of interaction with the ambient pressure. The structure is dependent on the expansion ratio of the nozzle, as described in Appendix C. Therefore, no diffusional mixing with ambient air occurs in the primary flame. The secondary flame is generated by mixing of the exhaust gas from the nozzle with the ambient air. The dimensions of the secondary flame are dependent not only on the combustion gas expelled from the exhaust nozzle, but also on the expansion ratio of the nozzle. A nitropolymer propellant composed of nc(0-466), ng(0-369), dep(0104), ec(0 029), and pbst(0.032) is used as a reference propellant to determine the effect of plume suppression. The burning rate characteristics of the propellants are shown in Fig. 6-31. Since the nitropolymer propellant is fuel-rich, the exhaust gas forms a combustible gaseous mixture with the ambient air. This gaseous mixture is ignited and afterburning occurs somewhat downstream of the nozzle exit. The major combustion products in the combustion chamber are CO, Hj, CO2, N2, and HjO. The fuel components are CO and H2, the mole fractions of which at the nozzle throat are co(0.47) and iH2(0.24).

Fig. 12.12 shows a typical set of flame photographs of a nitropolymer propellant treated with potassium nitrate. From top to bottom, the photographs represent KNO3 contents of 0.68%, 0.85%, 1.03%, and 1.14%. Each of these experiments was performed under the test conditions of 8.0 MPa chamber pressure and an expansion ratio of 1. Though there is little effect on the primary flame, the secondary flame is clearly reduced by the addition of the suppressant The secondary flame is completely suppressed by the addition of 1.14% KNO3. The nozzle used here is a convergent one, i. e., the nozzle exit is at the throat... 

Fig. 12.17 shows a typical set of afterburning flame photographs obtained when a nitropolymer propellant without a plume suppressant is burned in a combustion chamber and the combustion products are expelled through an exhaust nozzle into the ambient air. The physical shape of the luminous flame is altered significantly by variation of the expansion ratio of the nozzle. The temperature of the combustion products at the nozzle exit decreases and the flow velocity at the nozzle exit increases with increasing e at constant chamber pressure. 

It is evident that the standing pressure wave in a rocket motor is suppressed by solid particles in the free volume of the combushon chamber. The effect of the pressure wave damping is dependent on the concentrahon of the solid parhcles, and the size of the parhcles is determined by the nature of the pressure wave, such as the frequency of the oscillation and the pressure level, as well as the properties of the combustion gases. Fig. 13.25 shows the results of combustion tests to determine the effechve mass fraction of A1 parhcles. When the propellant grain without A1 particles is burned, there is breakdown due to the combushon instability. When... 

Fig. 13.25 Combustion instability is suppressed as the concentration of aluminum particles is increased (the average designed chamber pressure is 4.5 MPa).

In the case of ocular hypotony and a positive Seidel s sign with a formed anterior chamber in the early postoperative period, the treatment of choice is to discontinue the steroid to encourage wound closure and avoid secondary infection. The patient should be placed on a third- or fourth-generation topical fluoroquinolone. A topical aqueous suppressant may also be used to ensure secure wound closure.The patient is asked to limit activities and is given an eye shield to wear at night. An alternative treatment may include the use of a topical antibiotic and a 24-hour pressure patch with an eye shield while sleeping. If the wound feils to seal after several days to 1 to 2 weeks, surgical repair should be considered. 

---