Nuclear Energy Question Paper

Nuclear Energy

Course:Bachelor Of Science In Renewable Energy Technology And Management

Institution: Kenyatta University question papers

Exam Year:2009

KENYATTA UNIVERSITY
UNIVERSITY EXAMINATIONS 2009/2010
FIRST SEMESTER EXAMINATION FOR THE DEGREE OF BACHELOR OF
SCIENCE IN ENERGY ENGINEERING

SET 438:
NUCLEAR ENERGY

DATE: Wednesday, 23rd December, 2009
TIME: 4.30 p.m. – 6.30 p.m.
------------------------------------------------------------------------------------------------------------
INSTRUCTIONS:
•
This paper contains FIVE questions.
•
Answer question ONE and any other TWO.
•
Questions carry the marks as shown.
Question 1
a)
Distinguish between
i)
Nuclear Fission and
ii)
Thermo-Nuclear
(6 marks)
b)
i)
Explain what is meant by “Nuclear Fuel Cycles”

(2 marks)

ii)
Briefly explain the stages involved in the Uranium – plutonium fuel cycle
a
Nuclear
fuel
cycle
(10
marks)
c)
i)
A reactor with power rating of 1200 MWc operates with an overall
efficiency of 40%. The initial fissile fuel inventory is 6,000 kg, BR = 1.2
and ? = 0.25. Calculate the Linear and exponential doubling times.

(5 marks)
Page 1 of 3

ii)
A nuclear reactor for producing neutron beams is refueled with 10 kg of
enriched uranium which contains initially 91% of the fissile isotope 235U.
the reactor operates continuously at a constant thermal power of 57 MW
until the quantity of 235U is reduced to 70% of what was there initially, at
which point the 235U is too dilute for the chain reaction to continue. At
what rate are neutrons released and what is the longest possible period of
continuous running?
(Assume that the fission of one 235U nucleus releases an average 2 – 4
neutrons and 185 MeV of heat energy).

(7 marks)

Question 2
2.
a)
Using a well-labeled diagram, explain the working principle of boiling –
water
reactor.
(10
marks)

b)
A reactor produces electrical power of 300 MW. How much 235U is burnt
per day, if the plant efficiency is 30%. Assume that 200 MeV of energy
is
released
per
fission.
(10
marks)

Question 3
3.
a)
What kinds of wastes are formed during working periods in power
reactors. (3
marks)
b)
Explain the following terminologies, statements.
i)
Critical Mass and critical size of a reactor
(4 marks)
ii)
The
multiplication
factor
(3
marks)

c)
Calculate the macroscopic scattering cross section for natural uranium.
Given ,
? = 9
.
18 g /
3
cm percentage weight of 235U in natural uranium is
0.713, the rest being 238U. The scattering cross-section for 235U and 238U
isotopes being 15b and 13.8b respectively.

(11 marks)

Question 4
4.
a)
Explain the principle behind Neutron moderation by Elastic Scattering.

(8 marks)
Page 2 of 3

b)
Sketch plot q F(A, 0) versus angle of scattering in the L-system for
different
moderating
materials. (7
marks)

c)
A 1 MeV neutron is scattered through an angle of 45o in a collision with a
carbon nucleus in the L-system. Calculate the final neutron energy.

(5 marks)

Question 5
5. a) Under
critical reactor, explain:
i)
One-group
diffusion
theory
(6
marks)
ii)
Two-group
theory
(6
marks)
b)
The infinite multiplication factor for a BWR core of extra – polated
diameter 4.8 m and height 3.8 m is 1.2. Using the data given in table
calculate the effective multiplication factor using
i)
One-group
ii)
Modified one-group
iii)
Two-group and
iv)
The fermi-age critical equations
(8 marks)

Page 3 of 3

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