Reactor Startup Following Shutdown

How does xenon respond during a reactor startup following a shutdown ... 

Unsteady material and energy balances are formulated with the conservation law, Eq. (7-68). The sink term of a material balance is and the accumulation term is the time derivative of the content of reactant in the vessel, or 3(V C )/3t, where both and depend on the time. An unsteady condition in the sense used in this section always has an accumulation term. This sense of unsteadiness excludes the batch reactor where conditions do change with time but are taken account of in the sink term. Startup and shutdown periods of batch reactors, however, are classified as unsteady their equations are developed in the Batch Reactors subsection. For a semibatch operation in which some of the reactants are preloaded and the others are fed in gradually, equations are developed in Example 11, following. 

This chapter discusses several general pitfalls inherent in distillation startup and shutdown operations. Hazards and pitfalls specifically related to the nature of the chemicals processed (e.g., toxicity, flammability), the simultaneous startup/shutdown of the column with other units (e.g., reactors, furnaces), or to the overall startup/shutdown policy (e.g., operator training procedures) are outside the scope of this distillation text. The safe handling procedures of the relevant chemicals, as well as the overall startup/shutdovm policy, must be followed to cater for the latter hazards and pitfalls. 

Reactor startup consisted of setting the final system temperature and pressure with CO2 (or pure isobutane when CO2 was not used) and starting the olefin feed pump (defined as zero time). Prior to shutdown, the reactor was flushed with CO2 at reaction temperature and pressure until no hydrocarbons were observed in the effluent, following which the reactor was cooled and depressurized. 

The principal natural phenomena that influence transient operation are the temperature coefficients of the moderator and fuel and the buildup or depletion of certain fission products. Reactivity balancing may occur through the effects of natural phenomena or the operation of the reactor control system using the RCCs or chemical "shim." A change in the temperature of moderator or fuel (e.g., due to an increase or decrease in steam demand) will add or remove reactivity (respectively) and cause the power level to change (increase or decrease, respectively) xmtil the reactivity change is balanced out. RCC assemblies are used to follow fairly large load transients, such as load-follow operation, and for startup and shutdown. 

In the turbine-following-reactor control mode (i.e., turbine-follows-reactor), station loads are made to follow the reactor output. This is achieved by the steam generator pressure-control program, which adjusts the plant loads in order to maintain a constant steam generator pressure. This mode is used at low reactor power levels, during startup or shutdown, when the steam generator pressure is insensitive to reactor power. It is also used in some upset conditions when it may not be desirable to maneuver reactor power. 

Reactivity control for normal operabons of startup, load following, and shutdown is accomplished by bank (uniform) movement of nine control assemblies in the fuel region of the core (see Section 6.4.4.5). While the design requirement is for shutdown with up to two stuck rods, the worth of the control rods is such that any four of the nine assemblies can shutdown the reactor to cold subcritical conditions. Each assembly can be inserted into the core in three different ways a rod run-in by the PCS (a fast run-back), a fast run-in scram initiated by the RPS, and a gravity drop scram also initiated by the protection system. 

The PLS provides control and coordination of the plant during startup, ascent to power, power operation, and shutdown conditions. The PLS integrates the automatic and manual control of the reactor, reactor coolant, and various reactor support processes for required normal and off-normal conditions. The PLS provides control over the following reactor system functions ... 

How is the neutron density of the shutdown reactor changed during startup and the following rise to operating level ... 

After commissioning (Reactor Module and spaceship startup), a reactor shutdown would result in a loss of the spaceship (due to planned ejection of the solar panels following startup). 

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