I fail to see how ultraviolet radiation would produce deuterium. Since deuterium is hydrogen plus a neutron, and ultraviolet radiation is not a neutron stream. Now, if you have a neutron strain, say, from some decaying radionuclides in association with the water, I could see deuterium being produced. But not from ultraviolet radiation, which is electromagnetic waves.

If you don't care for reality, just wait a while; another will be along shortly. --A Rose