Thank you very much!
In fact I'm working for a nuclear engineering company. The term "burnup" is used very often here and it's usualy measured in MW day/t U as you mentioned.
I do not know why, but our guys additionally use the term that, if directly translated from Russian, sounds like "power production" or "energy generation".
One of the guys suggested "energy-producing" that he found in a certain dictionary, but I feel it sounds pretty awkward...
I was also explained that the term in question is the amount of energy produced over a cycle (the time that one core is in operation until the next reloading). The units of measurement that are used for the above magnitude is MW h (which looks pretty simlar to MWD).
The situation is that both burnup and "power production" could be used in a table with characteristcs and they need to be differentiated somehow.
My view here is that it does not look approprate if "burnup" is used two times in the same table, or in a paper, even with different units of measurements.
It may cause a lot of confusion.
Thank you again for the response and wonderful clarification.