The important information in this chapter is summarized below.Neutron Poisons SummaryA burnable neutron poison is a material that has a high neutron absorption crosssection that is converted into a material of relatively low absorption cross sectionas the result of neutron absorption.
A non-burnable neutron poison is a material that has relatively constant neutronabsorption characteristics over core life. The absorption of a neutron by one isotopein the material produces another isotope that also has a high absorption crosssection.Chemical shim is a soluble neutron poison that is circulated in the coolant duringnormal operation.
Burnable neutron poisons are used in reactor cores to compensate for the excesspositive reactivity of the fuel when the reactor is initially started up.Chemical shim has several advantages over fixed burnable poisons.
Has a spatially uniform effectPossible to increase or decrease amount of poison in the core duringreactor operationFixed burnable poisons have several advantages over chemical shim.
Can be used to shape flux profilesDo not have an adverse effect on moderator temperature coefficientTwo reasons for using non-burnable neutron poisons in reactor cores are to shape powerand to prevent excessive flux and power peaking near moderator regions.An example of a material that is used as a fixed non-burnable neutron poison is hafnium.
“We are the young generation, we are the young Malaysians, it is our future we are talking about, and we want a sustainable, green, beautiful, secure planet that we can show our own children with our very own eyes instead of just through pictures in history books – We want a future. And let us manage the waste”.
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