1. The problem statement, all variables and given/known data a - How many fission reactions would occur in 1 year of running of a nuclear reactor if the average power of the reactor is 778 MW? b - How many kilograms of U-235 would be needed to run the reactor for 1 year? c - What is the total change in mass for 1 year of running? I've found that 183.9 MeV are released from one fission reaction. 2. Relevant equations 1 megawatt = 10^6 J/s (1,000,000 J/s) 1 eV = 1.602 ×10^−19 J 1 year = 31,556,926 sec I don't know any others. 3. The attempt at a solution I know that 778 MW = 778,000,000 J/s. I do not know where to go from there. I'm not even sure if 183.9 MeV will be used in the answer to a, but I know the answer to a is required for b and b for c. I've tried multiplying 778,000,000 J/s by 31,556,926 sec to get just Joules. I've also tried dividing 778,000,000 J/s by 31,556,962 (don't know why - probably just out of desperation). From here I've done a multitude of things (such as dividing this answer by 1.602E-13 J) but nothing I've done is working. Someone please help, I've been at this one since 12:30 (now 4:30) and it's really getting me frustrated. - edit: 6:30pm - still working on this one, tried tons of Google searches to no avail, also posted on some other forums (although I don't know why -this one is the best ) Still can't get answer, someone please explain/help/respond!