Time dependent surface temperature of a nuclear fuel rod

[nukapprentice]

I was wondering if anyone has any actual data on the surface temperature of a fuel rod as a function of time. I am really curious as I am trying out a model I found which uses the fractional calculus. Or if anyone could point in the right direction to find said data that would be great as well.

 

[Astronuc]

I was wondering if anyone has any actual data on the surface temperature of a fuel rod as a function of time. I am really curious as I am trying out a model I made using the fractional calculus. Or if anyone could point in the right direction to find said data that would be great as well.

BWR or PWR?

Unless one has a thermocouple on the surface, the temperature must be derived from validated models, and possibly with temperature measurements from core inlet and outlet thermocouples.

In a BWR, there is some subcooling at the inlet, but much of the coolant is at saturated conditions, but the local coolant condition may be subcooled, saturated liquid, saturated liquid with nucleate boiling or liquid+steam in bulk boiling.

In PWRs, the coolant inlet temperature varies (285 to 293°C) according to the particular reactor. The exit temperature may vary from 315 to 330°C depending on the rating of the fuel rod. The coolant mass flux can vary from about 3500 to 3800 kg/m²-s.

The coolant surface temperature depends on the coolant temperature (which is a function of the coolant inlet temperature and enthalpy rise in the subchannel) and the heat transfer coefficient. Ideally, the coolant surface temperature is not much more than 340°C for long periods of time, in order to minimize the corrosion of the cladding. But predicted temperatures can be on the order of 345 to 347°C, with nucleate boiling, and this may promote crud (metal (Fe,Ni,Cr) oxide) formation, in addition to the oxidation of the cladding surface. A key issue in control of activation products is the control of crud through pH control in the primary system, and possibly the use of Zn-injection in the primary system.

 

[nukapprentice]

Thanks for the reply Astronuc and hope all is going well. I guess I wanted recorded data on the surface temperature because I found a model,(derived by Meyer in 1960 for wind tunnels) which used the fractional calculus to find that the surface heat flux is proportional to the surface temperature divided by the square root of time plus an integral involving the temperature(dimensionally also comes out to being divided by t^1/2). This means that the flux decreases as time increases, meaning that it goes to zero at a long enough time. The only way I think that the flux would eventually go to zero is when the water temp becomes equal to the surface temp, i.e. there is no potential for heat to transfer from the rod to the coolant. However since the water is flowing past the surface, heat should be still transferring. Any insight or advice would be greatly appreciated, thanks.

 

[nukapprentice]

Sorry, also meant to say that this is for a PWR.

 

[alphy]

I can provide some information on the time-dependent surface temperature of a nuclear fuel rod. First, it is important to note that the surface temperature of a fuel rod is affected by various factors such as the type of fuel, reactor design, and operating conditions. Therefore, the data on surface temperature may vary depending on these factors.

That being said, there are numerous studies and experiments that have been conducted to measure the surface temperature of fuel rods over time. These studies have shown that the surface temperature of a fuel rod increases as it is exposed to radiation and fission reactions, reaching a peak temperature and then gradually decreasing over time due to cooling mechanisms.

In terms of data, you can find published studies and reports from nuclear research organizations or academic journals that provide information on the time-dependent surface temperature of fuel rods. Additionally, some nuclear power plants may also have data on the surface temperature of their fuel rods, which may be available upon request.

Regarding the use of fractional calculus in modeling the surface temperature of fuel rods, it is a relatively new approach and may require further validation and refinement. However, it can be a useful tool in understanding the behavior of fuel rods and predicting their surface temperature over time.

I hope this information helps and guides you in your research. It is always important to consult reliable sources and conduct thorough research when working on scientific models and experiments. Best of luck in your endeavors.