ESTIMATION OF POWER PEAKING FACTOR AND THERMAL LIMITATION ON CORE PERFORMANCE OF NIGERIA RESEARCH REACTOR-1 (NIRR-1)
ESTIMATION OF POWER PEAKING FACTOR AND THERMAL LIMITATION ON CORE PERFORMANCE OF NIGERIA RESEARCH REACTOR-1 (NIRR-1)
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Date
2015-01
Authors
SALISU, ANAS MUHAMMAD
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Abstract
The Power Peaking Factor of a reactor is known to be the ratio of its peak heat flux to
the average heat flux around its core. This parameter was reported to be the key value
that dictates the maximum allowable power density of a fuel assembly. Investigation
shows that reactor core performance largely depends on the power peaking factor. It
was in recognition of the role of this importance parameter that measurements were
performed to estimate the Power Peaking Factor and core performance of the Nigeria
Research Reactor–1 (NIRR-1) core, which is Miniature Neutron Source Reactor
(MNSR). Our results show that the Power Peaking Factor for a preset neutron flux of
5.0×1011 cm-2s-1 ranges from 0.707 ± 0.293 to 1.014 ± 0.014 which yielded an average
value of the estimated power peaking factor to be lower than the expected value of 1.2
with more than 20%. The thermal limitation of NIRR-1 core was also obtained which
have an average of 12.6˚C. This is an in-build feature of NIRR-1 that compensates for
high negative temperature coefficient of reactivity in order to keep the reactor stable at
its preset power level. This is in agreement with safety requirements of the MNSR
which does not permit power excursion and occurrence of boiling. However, our results
show that the reactor stability is not applicable during startup and shutdown conditions.
It means that utilization of the Reactor must wait some few minutes after startup to
achieve stability and must stop some few minute before the shutdown. The results also
indicate the need to obtain a correction factor for samples that will stay in the reactor
for cyclic or longer period of irradiation provided there will be shutdown and start-up
in-between the irradiations. Our results also revealed that there is a strong dependence
of the reactor power on coolant temperature and rod position, which is in perfect
agreement with the design of the MNSR and findings of many workers in the area. The
computer program developed in this work for the determination of power peaking
factor using moderator parameters will not only serve as a new source code for
microcomputer control of the reactor peak power, maximum power factor and flux
distribution but will also make it possible for the microcomputer console to display real
time peak power level, maximum power factor thermal limitation of the reactor core, a
tool that is lacking in MNSR design.
Description
A THESIS SUBMMITTED TO POSTGRADUATE SCHOOL AHMADU BELLO
UNIVERSITY ZARIA NIGERIA
IN PARTIAL FULLFILMENT OF THE REQUIRMENTS FOR THE AWARD
OF MASTER OF SCIENCE DEGREE IN NUCLEAR PHYSICS OF THE
DEPARTMENT OF ;PHYSICS FACULTY OF SCIENCE, AHMADU BELLO
UNIVERSITY , ZARIA NIGERIA
Keywords
ESTIMATION,, POWER PEAKING FACTOR,, THERMAL LIMITATION,, CORE PERFORMANCE,, NIGERIA RESEARCH,, REACTOR-1,, (NIRR-1),