Info from; https://www.euronuclear.org/info/encyclopedia/f/fuelcomparison.htm

“With a complete combustion or fission, approx. 8 kWh of heat can be generated from 1 kg of coal, approx. 12 kWh from 1 kg of mineral oil and around 24,000,000 kWh from 1 kg of uranium-235.”

From: https://en.wikipedia.org/wiki/Nuclear_power
"Nuclear (fission) power stations, excluding the contribution from naval nuclear fission reactors, provided 13% of the world's electricity in 2012. The share of the world's primary energy supply, which refers to the heat production without the conversion efficiency of about 33 %, was about 5.7%. Its share of the global final energy consumption (actually useful energy, i.e. electric power) is below 2.5 % “

According to this site: https://en.wikipedia.org/wiki/Nuclear_power_by_country “In the year 2014 nuclear power plants generated 2410 TWh., of electricity.”

If I understand it correctly that the two thousand four hundred and ten Terawatts per hour, represent less than 2.5% of the total energy generated by nuclear power plants, then more than 70.5% of the power was wasted and converted into heat through various reactions with the energetic particles created by nuclear fission. Meaning that approximately 4,109.05 Terawatts worth of energy was generated per hour for a full year, 8766 hours* 4109.05 = 36,019,932.3 Twh total for the year.

If that amount of energy was producing heat for a period of, say 50 years, then I think that the amount of heat should be noticeable somewhere.
1 Terawatt = 1,000,000,000 kilowatts, 1 kilowatt = 1,000 watts.