# How much heat can radionuclides in HLNW generate?

1. Nov 10, 2015

### joknhial

The united kingdom has a 120 tons of nuclear waste, i have no idea which radionuclides constitute the largest portion, i want to know this. furthermore, if you can find which radionuclide it is, can you please tell me the decay mode it uses, its half life, and if it emits any decay heat. Thank you very much in advance. I know I don't live in the UK, but the UK has the largest civilian reserves for radioactive substances, hence the the reference. I'm thinking of devising a method, where nuclear waste is used to generate surplus energy. you send a highly volatile yet abundant liquid such as dry cleaner fluid or previously heated water ( has a lower boiling point) through a beta or alpha irradiated chamber with radionuclides that produce vast of amounts decay heat, in the range of 200 mega watts. this heated liquid will spin a turbine, generating electricity.

2. Nov 10, 2015

### Staff: Mentor

Thread moved to nuclear engineering forum.

We have some nuclear engineers here who can probably answer the specifics. But my gut tells me that while it's a nice idea, but an obvious one and so if it were economical it would already be done.

3. Nov 10, 2015

### joknhial

Hi, thanks for the quick reply, i was also thinking of that, it is a very simple idea indeed, however i have not taken the economical dimensions into my consideration. it would be great to hear back from some nuclear engineers.

4. Nov 11, 2015

### Staff: Mentor

This has been studied multiple times, and it is too expensive. Nuclear reactors are designed in the GW-range for a good reason, 200 MW thermal (where does that number come from?) wouldn't allow to sell enough electricity to make it worth building a power plant.

5. Nov 12, 2015

### gmax137

The decay heat decreases rapidly once the reactor is shut down. For a typical commercial power reactor here's a breakdown showing how the decay power reduces over time. This is the decay power, as a percent of the steady-state operating power of the reactor:

$$\begin{pmatrix} 1 & second & 6.599\\ 1 & hour & 1.454\\ 1 & day & 0.625\\ 1 & month & 0.182\\ 1 & year & 0.040\\ 3 & year & 0.013 \end{pmatrix}$$
So for a typical 3400 MW core, the decay power 3 years after shutdown is only ~450 kW.