The Reactor Vessel

BWRs operate at ca 7 MPa (70 bar) and 288°C. Some of the coolant passing through the core is converted into steam which is separated from the water with equipment inside the reactor vessel (see Eig. 2). The steam goes to the turbine generator while the water is recirculated back to the bottom of the core. A side stream is continuously purified using deminerali2ers and filters to control the water quality of the reactor water. EuU-flow condensate deminerali2ers... 

The BWR water chemistry parameters are given in Table 4 (19). Originally, no additives were made to feedwater—condensate or the primary water. The radiolytic decomposition of the fluid produced varying concentrations of O2 in the reactor vessel, ranging from about 200 ppb O2 in the reactor recirculation water to about 20 ppm O2 in the steam. Stoichiometric amounts of hydrogen were also produced, ie, 2 mL for each mL of O2. Feedwater O2 was about 30 ppb, hence the radiolytic decomposition of the water was a primary factor in determining the behavior of materials in the primary system and feedwater systems. 

Laboratory experiments have shown that IGSCC can be mitigated if the electrochemical potential (ECP) could be decreased to —0.230 V on the standard hydrogen electrode (SHE) scale in water with a conductivity of 0.3 ]lS/cm (22). This has also been demonstrated in operating plants. Equipment has been developed to monitor ECP in the recirculation line and in strategic places such as the core top and core bottom, in the reactor vessel during power operation. 

The key feature of the pressurized water reactor is that the reactor vessel is maintained above the saturation pressure for water and thus the coolant-moderator does not bod. At a vessel pressure of 15.5 MPa (2250 psia), high water temperatures averaging above 300°C can be achieved, leading to acceptable thermal efficiencies of approximately 0.33. 

Figure 8 shows a cutaway of the reactor vessel of the General Electric Company s model BWR/6 (52). Table 3 Hsts numerical data about this reactor. 

Addition Chlorination. Chlorination of olefins such as ethylene, by the addition of chlorine, is a commercially important process and can be carried out either as a catalytic vapor- or Hquid-phase process (16). The reaction is influenced by light, the walls of the reactor vessel, and inhibitors such as oxygen, and proceeds by a radical-chain mechanism. Ionic addition mechanisms can be maximized and accelerated by the use of a Lewis acid such as ferric chloride, aluminum chloride, antimony pentachloride, or cupric chloride. A typical commercial process for the preparation of 1,2-dichloroethane is the chlorination of ethylene at 40—50°C in the presence of ferric chloride (17). The introduction of 5% air to the chlorine feed prevents unwanted substitution chlorination of the 1,2-dichloroethane to generate by-product l,l,2-trichloroethane. The addition of chlorine to tetrachloroethylene using photochemical conditions has been investigated (18). This chlorination, which is strongly inhibited by oxygen, probably proceeds by a radical-chain mechanism as shown in equations 9—13. 

BWRs do not operate with dissolved boron like a PWR but use pure, demineralized water with a continuous water quality control system. The reactivity is controlled by the large number of control rods (>100) containing burnable neutron poisons, and by varying the flow rate through the reactor for normal, fine control. Two recirculation loops using variable speed recirculation pumps inject water into the jet pumps inside of the reactor vessel to increase the flow rate by several times over that in the recirculation loops. The steam bubble formation reduces the moderator density and... 

Fig. 1.1-6 SWBR LOCA Response The suppression pool absorbs the blowdown energy, the reactor vessel is depressurized by the depressurization valves and then flooded by the...

Seismic design basis for the reactor vessel (including attachments, pressure boundary, and CRD and internals). 

Generation and transport of heat within the core, including boiloff of water from the reactor vessel. 

Interaction of the core debris with residual water in the reactor vessel. 

Nuclear PSAs contain considerable uncertainty associated with the physical and chemical processes involved in core degradation, movement of the molten core in the reactor vessel, on the containment floor, and the response of the containment to the stresses placed upon it. The current models of these processes need refinement and validation. Because the geometry is greatly changed by small perturbations after degradation has commenced, it is not clear that the phenomcn.i can be treated. 

MKI The Mark I containment consists of two separate structures (volumes) connected by a series of l.irae pipes One volume, the dry well, houses the reactor vessel and primary system components. The other i oUmic is a torus, called the wetwell, containing a large amount of water used for pressure suppression and as, i heai sink. The Brunswick units use a reinforced concrete structure with a steel liner. All other M,uk 1 cnni.un ments are free-standing steel structures, The Mark I containments are inerted during plant oper.mon i. prevent hydrogen combustion. 

The risk from fatigue failure for the reactor vessel in the lower 2/3 of the core is negligible. 

In the industrial process, the chlorocarbon and liquid hydrogen fluoride feeds are pumped simultaneously into a complex liquid mixture of Sb(lII) and Sb(V) chlorofluondcs at temperatures in the 60-150 °C range The products are generally more volatile than the reactants and therefore distill preferentially from the reactor vessel, thus the reactor can be operated continuously. 

The cyanide reactor is critical because of the high temperatures dial arc iinoh cd. Overheating tlie reactor could result in uncontrollable combustion reactions or explosions." These uncontrollable combustion reactions or explosions could result in the physical breakdown of the reactor vessel by... 

---