Decay Heat

From shutdown to Criticality, and from there to full power

It is fission and fission all the way and the  neutron shower

In the reactor U-235 fissions to two parts of unequal weight

Releasing 200 MeV energy and two neutrons for chain as a bait

The fission products carry more neutrons than they need

They thus eject them out or an alpha or  beta as per need

They get the energy balance or adjust after another decay

Many times  product that comes is a simple gamma ray

 

Do not go by cute names of gamma and  baby new-tron

As terrible kids of fission causing heat in cauldron

The gamma, beta, neutron are small yet full of heat

Even when they say hello to atoms on friendly meet

On shutdown the power goes down  by exponential decay

But fission products keep the furnace hot by their own decay

The decay heat is a small fraction of  rated power

It is 7% of total and cooled by SDCP for all 24 hour

The decay heat goes down for months and for long

If not removed will  melt the fuel rod before long

For reactor on power, loss of cooling in cases three

Small, medium, large  loca push coolant in stages three 

SD cooling with a back up pump was never an issue

Till its drowing in tsunami water became a big issue

Now the SD cooling will get respect more than main

And be put on high pedestal with redundacy as item main