Module III:Basic principles of nuclear safety

  1. What is nuclear safety?

a)A set of international agreements to prevent nuclear war;

b)Procedures that must be followed when entering a nuclear power plant;

c)Protection of people and the environment from harmful effects of ionizing radiation;

d)Occupational safety in a nuclear power plant.

Answer: c).

  1. Why does a reactor need reactivity control system? (Two correct answers)

a)To start the reactor as quickly as possible;

b)To prevent the reactor from shutting down simultaneously;

c)Control the reactor power level during normal operation;

d)Provide for rapid shutdown and maintain the reactor subcritical, including in accident conditions;

e)In order to operate the reactor at the optimum economic level of power.

Answer: c), d).

  1. What is the amount of decay heat one hour after the reactor shutdown as a percentage of full power?

a)Approximately 10 %;

b)Approximately 1 %;

c)Approximately 0.1 %.

Answer: b).

  1. Which of the listed barriers confine radioactive fission products from uncontrolled release? (Three correct answers)

a)Fuel matrix;

b)Secondary system of the nuclear power plant;

c)Zirconium cladding of the fuel rods;

d)Physical security system of the nuclear power plant;

e)Fence around the plant;

f)Reactor coolant pressure boundary;

g)Site boundary.

Answers: a), c), f).

  1. Choose the three fundamental safety functions from the list!

a)Preventing unauthorized persons to enter the reactor building;

b)Control of reactivity;

c)Timely removal of radioactive waste from the plant;

d)Control of seawater for the condenser cooling at the intake;

e)Removal of heat from the reactor;

f)Uninterrupted external electric power supply;

g)Confinement of radioactive material;

h)International periodic safety reviews.

Answers: b), e), g).

  1. What were the most important contributing factors (root causes) towards the Chernobyl accident? (Two correct answers)

a)Using many fuel channels instead of a single reactor vessel;

b)Age of the reactor;

c)Positive void coefficient;

d)Lack of the leak tight containment building;

e)Insufficient number of operators in the control room;

f)Lack of safety culture.

Answers: c), f).

  1. What were the health and environmental consequences of the TMI-2 accident?

a)Serious contamination of the surrounding areas, evacuation from within 5 mile radius around the plant;

b)No detectable health effects on plant workers or the public;

c)Exposure of plant general population to radiation levels comparable to or a few times higher than annual levels of natural background.

Answer: b).

  1. Which event, triggered by earthquake and tsunami, was the root cause of the Fukushima accident?

a)Flawed reactor design;

b)Hydrogen explosion above the reactor containment;

c)Station blackout, resulting in the loss of the reactor's ultimate heat sink.

Answer: c).

  1. What is the fundamental safety objective as defined in the IAEA Safety Fundamentals document SF-1?

a)Protection against terrorist attacks;

b)Protectionof the people and the environment from harmful effects of ionizing radiation;

c)Prevention of melting the reactor core in case of an accident.

Answer: b).

  1. Name barriers for prevention of spread of radioactive materials used in the defence in depth concept.(Four correct answers)

a)Secondary system of the NPP;

b)Containment building;

c)Plant security fence;

d)Concrete walls of all buildings housing systems with radioactive media;

e)Fuel cladding;

f)Reactor cavity;

g)Primary coolant system;

h)All pressure vessels;

i)Piping with radioactive media;

j)Fuel matrix;

k)Concrete foundation of the nuclear power plant;

Answers: b), e), g), j).

  1. Listthe 5 levels of defence in depth!

Answer:

First level: prevention of abnormal operation and failures;

Second level: control of abnormal operation and detection of failures;

Third level: control of accidents within the design basis;

Fourth level: control of severe plant conditions including prevention of accident progression and mitigation of severe accident consequences;

Fifth level: mitigation of radiological consequences of significant off-site releases of radioactive materials.

  1. Who is legally committed by the Convention on Nuclear Safety?

a)Directors of national regulatory bodies;

b)Directors of nuclear power plants;

c)All States operating land-based nuclear power plants.

Answer:c).

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