is this mold on my kimchi or yeast?

That looks like mould (mold). Kimchi typically only goes mouldy when the vegetables are not submerged, which looks like is happening here, probably because of your choice of container. Use a deeper container like a jar so that all the solids are submerged in the liquid, and continually pack them down so they do not dry out. Alternatively, use a pickling weight or even just a clean pebble. The mould here looks extensive enough to have contaminated the whole container, so you should not eat any of it and throw it away, unfortunately.