How to keep magic from nuking everything while preserving the first law of thermodynamics

Let's say I'm a transdimensional or quasi-divine being whose pastime is acting as the patron for some mortal sorcerer who would very much like to turn lead into gold to impress their fellow corporeal beings. Being that I am benevolent and good and do not want my mortal playthings... i mean friends to be turned into radioactive dust, how might I turn all this energy into something less harmful, without violating the principle of conservation of energy as a whole?

(Specifically, I'm looking for a form of energy or matter that could be used to "store" the other deadly energy that a magic user might produce if they tried to transmute a heavier element into a lighter one. The presence of the transdimensional being is there to explain how all this is able to happen - they possess superior knowledge of physics and thus are aware of the dangers which they work to circumvent because they want to. For the purposes of this question they are constrained by the first law of thermodynamics, although they're obviously able to manipulate other laws of nature for this to even be a question.)

• Hard-science questions are for real-world physics. The first law of thermodynamics is not real world physics, it's a tiny part of it. if it is the only restriction you impose, you could have many answers such as ''teleport the energy somewhere else'', ''turn that energy back into some other matter that makes up for the mass difference'', ''release the energy anisotropically away from the magician'' ''release all radiation as alpha particles only''. All those satisfy the criteria in your question because, energy conservation, but none are hard-science. You need to reformulate or change the tag Sep 11, 2022 at 12:21
• Er... with magic? Alternatively couldn't you just make more gold? Sep 19, 2022 at 12:15

The options I see:

1: The type of energy.

2: The amount of energy over time.

Imagine if your lead to gold process releases its energy in the form of light, over a longer time. That way the type of energy release isnt dangerous unless in large amounts and you control that amount through the time it takes.

You could spread that energy release over multiple sources. For example add the release in the form of heat and ask your playthings to place it in streaming water or some other heatsink in order to increase the amount of energy that can be released per time unit to speed up the process.

Do it in a stream.

Nuclear power plants cool themselves with water. You can do the same, with a stream or a large body of water. Water is very good at absorbing heat and radiation, and could absorb whatever excessive heat you made.

You can presumably control how it decays, so you can produce weird decay products that absorb most of the nuclear energy. Protons and neutrons, for example, don't have binding energy on their own so if you just yeet out a couple protons then you just need to add whatever energy to yeet them.