Unit 11 : Random Quiz

What is the primary function of the moderator in a nuclear reactor?

To absorb excess neutronsTo shield the reactor from radiationTo cool the fuel rodsTo slow down neutrons to thermal energies

What condition defines ignition in a fusion plasma?

The confinement field is switched offThe plasma maintains its temperature through α-particle heating aloneThe plasma becomes electrically neutralThe plasma converts entirely to helium

Why is fission more likely for even-even nuclei compared to odd-A nuclei?

Even-even nuclei are more stable and more likely to reach configurations favorable for fissionEven-even nuclei can emit more beta particlesEven-even nuclei have higher Z, favoring Coulomb repulsionOdd-A nuclei have more neutrons, which suppress fission

Why does fission of heavy elements release energy?

Fission creates more protons than neutronsFission breaks quark bonds, releasing energyThe nucleus absorbs thermal energy before splittingThe fission products have higher binding energy per nucleon than the original nucleus

What is the Lawson criterion used for?

To assess fuel efficiency in fission reactorsTo determine the minimum confinement conditions for net energy gain in fusionTo calculate the neutron flux in a reactorTo measure plasma temperature stability

What allows CANDU (PHWR) reactors to use natural uranium fuel?

Operating at higher pressure than PWRsUse of heavy water as moderator and coolantSeparate moderator and coolant systemsUsing graphite as a moderator

Which component of a nuclear power plant converts thermal energy into electrical energy?

Coolant pumpModeratorSteam turbineControl rods

Which reactor type uses ordinary water for both moderation and cooling?

CANDU reactorAdvanced gas-cooled reactor (AGR)Boiling water reactor (BWR)Pressurised water reactor (PWR)

What is a disadvantage of BWRs compared to PWRs?

They use graphite moderators, which are less efficientThey require plutonium fuelRadioactive steam goes directly to turbinesThey cannot follow electrical load demands

Which facility first demonstrated breakeven in a fusion shot using inertial confinement?

Joint European Torus (JET)SPARCNational Ignition Facility (NIF)ITER

What is a key safety feature of a PWR in the event of overheating?

Boiling of the coolant reduces moderation, lowering the fission rateThe containment vessel absorbs neutronsThe control rods are automatically ejectedThe pressure vessel bursts to release steam

What is a major advantage of aneutronic fusion reactions?

They are more efficient at lower temperaturesThey occur spontaneously in natureThey use heavier elements which are more abundantThey produce only charged particles, which can be converted to electricity directly

What is the role of a startup source in a reactor?

To remove delayed neutrons from the coreTo initiate a chain reaction in a subcritical coreTo cool the reactor during initial heat-upTo keep the reactor supercritical during operation

What physical phenomenon allows fusion to occur at temperatures lower than the classical Coulomb barrier?

Quantum tunnellingMagnetic resonanceElectron screeningGravitational attraction

Why are fast breeder reactors not widely used commercially?

They do not utilize uranium fuelThey cannot achieve criticalityThey are expensive and complex to operate safelyThey produce too much radioactive waste

What challenge arises from the neutron produced in d-t fusion?

It triggers runaway reactionsIt damages the tokamak’s magnetic field coils directlyIts energy must be captured to generate powerIt makes magnetic confinement impossible

Why is \(^{238}\)U not easily fissioned by thermal neutrons?

\(^{238}\)U has too many protons\(^{238}\)U always decays by alpha emissionNeutron capture in \(^{238}\)U results in a compound nucleus with excitation energy below the fission barrierThe neutron cross section is too large

What allowed natural nuclear reactors to operate at Oklo two billion years ago?

The uranium was already enriched artificiallyThe ore contained plutoniumNatural uranium then had a higher proportion of \(^{235}\)UCosmic rays triggered continuous fission

What condition makes a nucleus unstable to spontaneous fission in the liquid drop model?

The surface energy term becomes zeroThe number of neutrons is greater than protonsThe ratio Z²/A exceeds a critical valueThe nucleus is at absolute zero temperature

Which reactor type uses steam from the reactor core directly to drive the turbines?

Boiling water reactor (BWR)Advanced gas-cooled reactor (AGR)Pressurised water reactor (PWR)Pressurised heavy water reactor (PHWR)

Unit 11 : Random Quiz#