Question

Identify 3 important systems associated with boiling water reactors and named the primary purpose of each.

Name the systems that removes impurities from the reactor water

Name the purposes of the off gas system

Identify the plant system designed to maintain or restore core submersion in the event of loss of coolant accident

Identify the source of high radiation levels in the RHR system during system shut down

Name the purposes of the automatic depressurization system

Answer 1

Ques 1 Basic power cycles in nuclear power plants(A) Single-loop cycle; it represents a boiling-water reactor (BWR), but it could also represent a direct-cycle, high-temperature gas-cooled reactor (HTGR) if helium were substituted for steam.

(B) Two-loop cycle; the primary loop depicted here could constitute a pressurized-water reactor (PWR), a CANDU pressurized heavy-water reactor (PHWR), or a helium HTGR.

(C) Three-loop cycle; this is found only in sodium-cooled reactors where an intermediate loop of nonradioactive sodium is provided between the radioactive primary loop and the steam generator.

Ques 2.Pressurized-water reactor (PWR)  In the PWR, water at high pressure and temperature removes heat from the core and is transported to a steam generator. There the heat from the primary loop is transferred to a lower-pressure secondary loop also containing water.

Ques 3. The purposes of the offgas system are to:

• establish and maintain a vacuum in the main condenser to improve cycle efficiency.

• process non-condensible gases to limit the release of radioactive gases to the atmosphere.

The offgas system processes and controls the release of gaseous radioactive effluents from the condenser to the site environs so that the total radiation exposure to persons outside the protected area do not exceed the limits. The offgas system is functionally classified as a power generation system.

Ques 4. The residual heat removal (RHR) system is a versatile high capacity low pressure system that can be used for cooling and/or inventory control. The functional classification of the RHR System is that of a safety related system.

Ques 5. Decay heat is the heat released as a result of radioactive decay. This heat is produced as an effect of radiation on materials: the energy of the alpha, beta or gamma radiation is converted into the thermal movement of atoms.Decay heat occurs naturally from decay of long-lived radioisotopes that are primordially present from the Earth's formation.

Ques 6. The purpose of the Automatic Depressurization System (ADS) is to rapidly lower reactor pressure to allow low pressure injection sources to maintain reactor water level above the Top of Active Fuel (TAF). ADS is an Emergency Core Cooling System (ECCS) and is the backup system to the High Pressure Coolant Injection (HPCI) system. The functional classification of ADS is a safety related system. Its regulatory classification is an engineered safeguards system.