1.       Electricity produced from a nuclear power plant is similar to the other plants with the following exception

The source of the energy; EX coal & Natural gas is combustion, Nuclear is fission.

2.     What is the fissionable material used in commercial nuclear power plants?

Because uranium 235 in its natural form is not strong enough to last the entire cycle needed between outages (18-24 months).

1.       In a nuclear power plant, what are the 3 types of safety and describe each of the 3.

1.       Nuclear (3 Barriers)

2.       Radiological (contamination/exposure)

3.  Industrial (gloves, ect)

1.       What are the three fission product barriers used to prevent the release of radioactive fission products to the environment?

1.       Fuel Cladding, protects Uranium 235 from leaking into Reactor water

2.       Reactor Vessel and Pipe system, prevents Reactor Water from contaminating secondary loop.

3.       Containment structure, prevents radiation from leaking in catastrophic event or LOCA

  List 3 sources of power for nuclear power plants emergency electrical buses.

1. main generator output- UAT

2. RAT-offsite power

3. Diesel Generators

 Why is reactor core submergence so important and what systems provide emergency water to the primary system in the event of a Loss of Coolant Accident?

It is important to keep the core covered to prevent overheating. If the water level does not cover the core the zirconium will melt, allowing for the fuel pellets to pool at the bottom creating a critical mass. This critical mass will have an uncontrollable fission rate which will result in a catastrophic disaster.

1.       Boric acid is used in what type of plant to control fission rate and power level?

1.       List 5 examples of a component used in a nuclear power plant.

a.      Steam Generator

b.      breaker

c.       RCP

d.      motor

e.      breaker

1.       Define the terms critical, subcritical and super critical  as they relate to a nuclear power plant

Critical reactor is self sustaining fission rate. That is 1 of the 2.43 neutrons from a fission goes on to cause another fission....power rate and heat generation rate is constant. Sub critical is a lowering fission rate and sub critical is an increasing fission rate.

1.       What is the purpose of a Jet pump in a BWR?

a.      The Jet pumps purpose in a BWR is to increase flow, it is said to increase the rate of water flow x7 the normal rate. Increase flow rate means increased heat removal and subsequently increase power production.

1.       What are the 2 systems between the main condenser and the reactor of a boiling water reactor?

a.      The two systems between the main condenser and the reactor in a BWR are  the condensate and feedwater system.

1.       Explain the concept of redundancy or back up to backs up in a nuclear power plant and include why this concept is important to safety.

a.      The purpose of redundancy is to lower the probability of a faulty valve or pipe line causing a catastrophic event.

1.       Describe the 3 loops of a power plant and state whether each is open or closed.

a.      Primary- Closed, contains reactor, pressurizer. Where nuclear fission occurs, heat is transferred from Primary to the Secondary loop within the steam generator.

b.      Secondary-Closed, consists of steam generator, steam turbines, and condenser. Once heat is transferred from Pressurized reactor, the water within generator becomes steam goes through main steam line (containing chevrons to remove possibility for impingement), and then through the turbine (high and low) with a pass through the MSR. Once the steam has passed through the turbines (where the turbine powers the generator which produces electricity), the steam is condensed in the condenser and recirculated back to the steam generator. The condenser is cooled by the…

c.       Circ Water- cools the water that passes through the condenser after making its way through the H &L turbines. This water is sucked in from a major source (ex lake Michigan or river), and feed back out once it has cooled the steam in condenser. This water is desired at as low as possible temperatures, a reason lakes are more common than rivers, deeper colder water is accessible.

1.       What is the source of energy for the feed water heaters?

Extraction steam from the main turbine.

1.       What material is the fuel cladding made of?

a.      Zirconium

1.       To lower reactor power, control rods must be

a.       Nitrogen gas is used to piston the rods into the core in a BWR. In a PWR the motive force is gravity, after the electromagnets are automatically de-energized (occurs during a SCRAM).

a.      Because the nuclear fission process has decay heat for long after the reactor has been shut down, the control rods are inserted, and boron is used as a neutron poison. This decay heat is still extremely hot and can cause damage to the core and damage the integrity of the plant.

1.       Why must the water in the reactor coolant system always be on high purity?

a.      Because high purity water will prevent impingement (due to particles), corrosion, and erosion. All three of these things are extremely damaging to the plants vital system impingement especially for the turbines, and corrosion and erosion to the Primary and Secondary loops.

1.       What valves close in the event of a steam line rupture in the turbine building?

a.      The stop valves and control valve

1.       What system is used in a Boiling Water Reactor (BWR) to control the fission rate while at power?

a.      Chemical Volume and Control System (CVCS)

1.       Why is the main condenser maintained at a vacuum?

To have a higher differential pressure across the turbine

1.       What is the purpose of the extraction non return valves?

The purpose of the extraction non return valves between the turbine and condenser is to prevent back flow (it is a check valve).

a.      Start up/ heat up

b.      Pre warm steam piping

c.       Cool plant down/ depressurize

1.       What is the purpose of demineralizers?

1.        List 3 support systems for an emergency diesel generator.

a.      fuel oil, lube oil, cooling warer, starting air, elecrical supply, combustion air

1.       Why must the delivery steam to the main turbine be dry steam (no moisture)?

To prevent impingement caused by water particles hitting the turbine blades at 1800RPM. Dry steam has gone through chevrons in the MSL to prevent impingement and guarantee that it is dry when it reaches the turbine.

1.       List 3 pumps in a nuclear power plant and state the purpose of each

1. Jet pump- to increase the flow in a PWR reactor x7.
2. centrifugal pump
3. positive displacement pump

1.       Why must impurities be removed the reactor coolant maintained highly pure?

a.      To prevent corrosion, erosion, and radiological exposure (particles become hot particles).

1.       Why must decay heat be removed from a reactor after shutdown?

a.      The decay heat must be removed to prevent the zirconium/zircaloy from melting and allowing for a critical mass to build at the bottom of the core.

1.       What are the automatic start signals for a Emergency Diesel Generator?

a.      Loss of offsite power

b.      LOCA

1.       What is the fissionable isotope that in used to generate nuclear power?

1.       In a BWR, what valves are opened in the event of a small break loss of coolant accident when there is insufficient high pressure Emergency Core Cooling flow to maintain the reactor core covered?

a.      HPCI, RHR

1.       List 5 modes of the Residual Heat Removal (RHR) system

a.      Low Pressure Cool injection mode

b.      Shutdown cooling mode

c.       Suppression pool cooling

d.      Drywell spray

e.      Fuel pool cooling assist

a.      Fuel pool cooling assist

a.      Low Pressure Cool injection mode

b.      Shutdown cooling mode

1.       What are the low pressure ECCS systems for both a BWR and PWR.?

a.      HPCI in a BWR, S.I.

a.      A Terry Turbine

1.       When reactor power is raised from 20 to 35 percent power, which best describes the response of the main turbine?

a.      Turbine Control Valves open due to an increase in steam header pressure and main generator output (Megawatts) increases

1.       In a Boiling Water Reactor why are there walls around the main turbine at power?

a.      Because the main turbine at power is not separated like a PWR in a second, non contaminated loop. The steam flowing through the turbine is radioactive, and requires shielding.

1.       Why is the primary containment of a BWR inerted?

a.      To prevent a hydrogen explosion.

a.      The BWR control rods are inserted from ground upwards, defying gravity while a PWR drops in their rods.

b.      BWR control rods are inserted using Nitrogen gas as a driving force, while gravity helps PWR rods insert in event of SCRAM.

1.       What gas cools the main generator and list 2 reasons why this gas is used.

a.      Hydrogen. It is cheaper, has a high specific heat and is 7-10x better than regular air.

1.       Where does the High Pressure Coolant Injection (HPCI) system get its motive force to operate?

1.       Why are there two isolation valves on each containment penetration?

a.      There are two valves to act as redundancy in case the first valve fails the second can be used. These valves also have a gas chamber filled w/ nitrogen to prevent Hydrogen explosions.

a.      1. Insert rods

b.      2. inert containment

c.       3. isolation valves

a.      Suction source for ECCS

b.      Replenish non condensable

c.       Absorb energy during a LOCA

1.       Where is the most likely location of a primary to secondary leak in a Pressurized Water Reactor (PWR)?

a.      Steam generator.

a.      Stand By Liquid Control System

a.      They are re-energized and the electromagnets work to pull the rods out of the core.

a.      The purpose of the BIT is to rapidly release boron into the reactor coolant loop when needed.

1.       What are two functions or purposes of the pressurizer in a PWR.?

a.      To absorb energy in the form of steam, it acts as a flux area. Excess flows into the pressurizer and increases pressure.

b.      To keep the primary loop pressurized.

a.      Three gases, none of them at the same time. Hydrogen is typically within the main generator as a cooling agent. To remove the hydrogen for outage C02 must be used to chase the hydrogen out. Then Oxygen floods out the c02. CO2 purpose is to act as a buffer, and constantly be between hydrogen and oxygen.

1.       What are the two high pressure Emergency Core Cooling Systems used at a PWR?

a.      HPCI and Core Spray

1.       What functions do the bearings on the main turbine serve or provide.

a.      The bearings prevent side by side motion along the main turbine shaft.

1.        What system prevents the leakage of gas out of the main generator?

a.      Oil seal system/ Pressurized oil system.

1.        Explain the Davis Besse reactor head event.

a.      The reactor head was corroded due to boric acid to a point of only 3/8” of stainless teal left on reactor head. The cause was neglect of acknowledging increased radiation levels and other signs to stop and evaluate.

1.       What valves close on a turbine trip signal, such as low lube oil pressure or high vibration, to stop the flow of steam to the main turbine?

a.       Main Steam Isolation Valves (MSIVs)

b.       Extraction non return valves

c.       Turbine stop valves

d.       Turbine control valves

a.      To remove any water from the steam to enforce only dry steam is traveling through the turbines.

a.       To keep the shaft from bowing and dissipated evenly when shut down.

1.       As reactor power is lowered from 100 to 90 percent power the following will occur.

1.       Explain when the Automatic Depressurization System (ADS) of a BWR would be used and why.

a.      The ADS system is used if the HPCI or LPCI fail. If the HPCI fails the ADS switches the high pressure loca to low pressure to enact the LPCI system. It does this by removing water from the core so the LPCI system will act to replace a loss of inventory.

1.       What element is used to inert the containment atmosphere of a Boiling Water Reactor

1.       What are the 3 elements required to generate electricity.

Conductor (Does not have to be current carrying to generator action)

Magnetic Field

Relative Motion

1.       List 3 applications of heat exchangers in either a BWR or PWR plant.

Condensor

Steam generator

MSR (moisture separator reheater)

RHR (residual Heat Removal) heat exchanger

Excess letdown heat exchanger

Letdown heat exchanger

Seal water heat exchanger

CCW (component cooling water) heat exchangers

Containment spray heat exchangers

Reactor coolant pump seal water heat exchanger

Spent fuel pit heat exchanger

TACW (turbine auxiliary cooling water) heat exchanger

Blowdown treatment heat exchanger

Regenerative heat exchanger

1.       Explain 2 uses or functions of valves in power plants.

To isolate or stop system flow.

To unisolate or allow system flow

To throttle flow at the desired level between full open and full closed.

1.       What is the function of the pressuirzer spray valve in a PWR.?

Pressure excursions can be controlled by using the spray valve which will spray relatively cooler water into the steam blanketed area causing the steam blanket to cool condense and reduce pressure.

Boron concentration control and control rods.

Why is it necessary to have both high and low pressure Emergency Core Cooling systems?

So that the appropriate system with the appropriate capacity can keep the core covered and cool.

In the case of a small line break or small leak the system pressure will remain high requiring a high pressure ECCS system is needed to pump water into the primary system, the high pressure system has a lower flow rate as does the small line or small leak.

In the case of a Large line break or Large leak the system pressure will be lost through the hole so a low pressure ECCS system is needed to pump water into the primary system, the low pressure system has a high flow rate as does the Large line break or Large leak.

Condense the steam exhausted from the turbine so that it can be reused and then heat it to maximize plant efficiency while raising the system pressure in steps to pump the water back into the steam generators.

Circ water pump

Decrease, Lower

The Steam Generator

Maintain  system pressure high enough to prevent boiling in the core and acts as a surge volume so that small changes that would occur with changes in water volume do not cause a drastic change in system pressure.

It is normally controlled by cycling on and off heaters.  Pressure excursions can also be controlled by using the spray valve which will spray relatively cooler water into the steam blanketed area causing the steam blanket to cool condense and reduce pressure.

The main turbine bearings support a shift weighing several tons rotating at 1800 RPM the amount of friction that would be created without lubrication would cause them to overheat and melt.

Explain how hydrogen in the main generator is prevented from leaking out.

90.     What is the purpose of the extraction non return valve in a BWR?

It is a check valve that prevents backflow of steam into the low pressure turbine.

Refueling water storage tank and the reactor sump

Each generating has two EDGs which are individually capable of providing reliable AC power with sufficient capacity to operate the ECCS (provide power to the emergency bus). The EDGs perform this function in order to ensure safe shutdown of the reactor and mitigation of the following events:

• Loss Of Offsite Power (LOOP)

• LOOP with Safety Injection (SI)

• LOOP with Containment Spray (CS)

Blowdown is the removal of water from a boiler. Its purpose is to control boiler water parameters within prescribed limits to minimize scale, corrosion, carryover, and other specific problems. Blowdown is also used to remove suspended solids present in the system. These solids are caused by feedwater contamination, by internal chemical treatment precipitates, or by exceeding the solubility limits of otherwise soluble salts.

Main Stem Isolation Valves.

To ensure positive isolation of containment in case a pipe shear between a valve and the containment on either side or a single component failure (redundant systems).

1. inert containment

2. isolation valves

3. insert rods

What cools the main generator stator bars?