Neutron poison

The variation in boron concentration allows control rod use to be minimized, which results in a flatter flux profile over the core than can be produced by rod insertion. The flatter flux profile occurs because there are no regions of depressed flux like those that would be produced in the vicinity of inserted control rods. This system is not in widespread use because the chemicals make the moderator temperature reactivity coefficient less negative.<ref name="doe-31">DOE Handbook, p. 31.</ref> All commercial PWR types operating in the US (Westinghouse, Combustion Engineering, and Babcock & Wilcox) employ soluble boron to control excess reactivity. US Navy reactors and Boiling Water Reactors do not.{{Citation needed|date=May 2012}} One known issue of boric acid is that it increases corrosion risks, as illustrated in a 2002 incident at [[Davis-Besse Nuclear Power Station]].<ref>{{cite web |url=http://www.gao.gov/new.items/d061029.pdf |title=Report to Congress |author=United States Government Accountability Office |year=2006 |page=1 }}</ref>

The variation in boron concentration allows control rod use to be minimized, which results in a flatter flux profile over the core than can be produced by rod insertion. The flatter flux profile occurs because there are no regions of depressed flux like those that would be produced in the vicinity of inserted control rods. This system is not in widespread use because the chemicals make the moderator temperature reactivity coefficient less negative.<ref name="doe-31">DOE Handbook, p. 31.</ref> All commercial PWR types operating in the US (Westinghouse, Combustion Engineering, and Babcock & Wilcox) employ soluble boron to control excess reactivity. US Navy reactors and Boiling Water Reactors do not.{{Citation needed|date=May 2012}} One known issue of boric acid is that it increases corrosion risks, as illustrated in a 2002 incident at [[Davis-Besse Nuclear Power Station]].<ref>{{cite web |url=http://www.gao.gov/new.items/d061029.pdf |title=Report to Congress |author=United States Government Accountability Office |year=2006 |page=1 }}</ref>

Soluble poisons are also used in emergency shutdown systems. During [[SCRAM]] the operators can inject solutions containing neutron poisons directly into the reactor coolant. Various aqueous solutions, including [[borax]] and [[gadolinium nitrate]] (Gd(NO₃)₃·{{mvar|x}}H₂O), are used.<ref name = doe-31/>

Soluble poisons are also used in emergency shutdown systems. During [[SCRAM]] the operators can inject solutions containing neutron poisons directly into the reactor coolant. Various aqueous solutions, including [[borax]]{{citation needed}}, [[sodium borate|sodium polyborate]], and [[gadolinium nitrate]] are used.<ref name = doe-31/>

==References==

==References==