- #1
Lisa!
Gold Member
- 649
- 98
Could you please explain about the role of reactivity in reactors?
Lisa! said:Could you please explain about the role of reactivity in reactors?
Thanks a million you Dr. Greenman.Morbius said:Lisa,
Reactivity is the term given to the quantity that tells you how much the
neutron economy is out of balance.
If a reactor is exactly critical - that is, the neutron production is exactly
equal to neutron destruction - then the reactivity is zero.
If the reactivity is positive - then the reactor is supercritical. If the
reactivity is negative - then the reactor is sub-critical.
The Reactivity is defined as the ratio of an adjoint weighted average
of the excess neutron production divided by an adjoint weighted average
of the fission production.
The quantity "reactivity" is one of the terms in the "Point Kinetics"
equations, which is a zero-dimensional set of equations that describe the
transient behavior of a reactor.
Look up "point kinetics equations" in a reactor physics text.
Dr. Gregory Greenman
Physicist
theCandyman said:Thanks for posting that, Astronuc. I wish the book I had used provided some examples, I was lost most of the time for problems. I guess the author wanted students to understand the concept and not "plug and chug" problems with an equation.
Lisa! said:.Anyway I try to find a suitable article and I may understand it coz you made it more understandable.
Astronuc said:I think Koclas means that we use digital computation (computer models) rather than analytical models.
The lastest technology is 3D-spatial kinetics models used in the core simulators like Studsvik's SIMULATE-3K ...
The nuclear industry is small world. I know of Kord Smith, but I have not had the pleasure of meeting him. IIRC, he is married to a friend's cousin. My friend also trained with me in Nuclear Engineering.That brings another one of my contemporaries at M.I.T. into the picture;
Kord Smith. Kord works for Studsvik Scandpower - and has been the
"developer in chief" for Studsvik's reactor analysis codes like SIMULATE-3K.
Astronuc said:BTW Greg, Fred said - Hi! Too bad you couldn't make it to the conference.
theCandyman said:Morbius, those equations look really daunting, mostly because I do not recognize many of the symbols .
Reactivity refers to the ability of a nuclear reactor to sustain or control a chain reaction of nuclear fission. It is a measure of how much the number of fission reactions in the reactor changes with time.
The reactivity of a reactor determines its power output and the rate of fission reactions. A high reactivity can lead to an increase in power output, while a low reactivity can cause a decrease or shutdown of the reactor.
Reactivity is crucial in maintaining a stable nuclear reaction by balancing the rate of fission with the rate of neutron absorption. A reactor with a high reactivity will have a higher rate of fission, while a reactor with a low reactivity will have a lower rate of fission, resulting in a stable reaction.
Reactivity is controlled through the use of control rods, which absorb neutrons and can be inserted or withdrawn from the reactor core to adjust the reactivity. Other factors that can affect reactivity include changes in reactor temperature and fuel composition.
Yes, an uncontrolled reactivity can lead to a rapid increase in power output and potentially cause a nuclear reactor to overheat or even melt down. For this reason, strict safety measures and regulations are in place to monitor and control reactivity in nuclear reactors.