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০০। "Critical mass" is the minimum mass of nuclear fissile material required for the
- ক) sustainment of chain reaction.
- খ) power generation on commercial scale.
- গ) economic power generation.
- ঘ) none of these.
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০১। β-rays emission in radioactive disintegration is always accompanied by the emission of
- ক) γ-rays
- খ) α-rays
- গ) neutrons
- ঘ) none of these
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০২। 'Heavy water' is termed as 'heavy' because it is
- ক) denser than water.
- খ) an oxide of deuterium.
- গ) a heavy liquid.
- ঘ) an oxide of heavier isotope of oxygen.
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০৩। 'Light water' used as a coolant in nuclear reactor is nothing but
- ক) ordinary water.
- খ) mildly acidic (pH = 6) water.
- গ) mildly alkaline (pH = 8) water.
- ঘ) none of these.
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০৪। 75% of a radioactive element decays in 6 hours. Its half life period is __________ hours.
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০৫। A boiling water reactor is the one, in which the
- ক) coolant water is allowed to boil in the core of the reactor.
- খ) coolant water, after being heated in the reactor core, generates steam in a boiler.
- গ) pressurised water is pumped into the core.
- ঘ) fuel and the coolant are thoroughly mixed to form a homogeneous solution.
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০৬। A control rod
- ক) should have small absorption cross-section.
- খ) is generally made of boron, hafnium or cadmium.
- গ) should have large absorption cross-section.
- ঘ) both (b) and (c).
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০৭। A fast breeder reactor
- ক) uses natural uranium as fuel.
- খ) does not require a moderator.
- গ) both (a) and (b).
- ঘ) neither (a) nor (b).
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০৮। A fast breeder reactor
- ক) utilises fast neutrons for causing fission.
- খ) converts fertile material (e.g., U-238) into fissile material (Pu-239).
- গ) normally employs molten sodium as coolant.
- ঘ) all (a), (b) and (c).
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০৯। A fast breeder reactor employs
- ক) graphite as moderator.
- খ) water as coolant.
- গ) molten sodium as coolant as well as moderator.
- ঘ) U-235 as fuel.
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১০। A fertile material is the one, which can be
- ক) converted into fissile material on absorption of neutron.
- খ) fissioned by slow (thermal) neutrons.
- গ) fissioned by fast neutrons.
- ঘ) fissioned by either slow or fast neutrons.
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১১। A heterogeneous reactor is the one, in which the moderator and the
- ক) coolant are different materials.
- খ) coolant are present in different phases (e.g., heavy water and graphite).
- গ) fuel are present in different phases (e.g. uranium and heavy water).
- ঘ) none of these.
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১২। A homogeneous reactor is the one, in which the
- ক) fissile atoms are evenly distributed throughout the mass of nuclear reactor.
- খ) same substance (e.g. heavy water) is used as moderator & coolant.
- গ) the fuel and the moderator is mixed to form a homogeneous material.
- ঘ) all (a), (b) and (c).
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১৩। A moderator __________ the neutrons.
- ক) slows down
- খ) absorbs
- গ) accelerates
- ঘ) reflects
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১৪। A nuclear reactor can't be used for
- ক) the production of radioisotopes.
- খ) supplying intense fields or beams of neutron for scientific experiments.
- গ) marine ship propulsion.
- ঘ) none of these.
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১৫। A pressurised water reactor (PWR) uses pressurised water as a
- ক) coolant.
- খ) working fluid in power turbine.
- গ) moderator.
- ঘ) none of these.
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১৬। A radioactive isotope undergoes decay with respect to time following __________ law.
- ক) logarithmic
- খ) exponential
- গ) linear
- ঘ) inverse square
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১৭। A radioactive substance does not emit
- ক) α-ray
- খ) proton
- গ) position
- ঘ) β-ray
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১৮। A thermal nuclear reactor compared to a fast breeder reactor
- ক) uses slower neutrons for fission.
- খ) uses faster neutrons for fission.
- গ) gives higher power density.
- ঘ) requires less fuel to run at the same power level.
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১৯। Absorption/scattering cross-section of an element is expressed in "barn", which is equivalent to
- ক) 10-24 cm2
- খ) 10-12 cm
- গ) 1 Angstrom
- ঘ) 10-24 cm