Complex sentence: Even with this level of plutonium consumption, light water reactors consume only part the plutonium and minor actinides they produce, and nonfissile isotopes of plutonium build up, along with significant quantities of other minor actinides.
Split into simpler sentences: Even with this level of plutonium consumption, Light Water Reactors are not able to consume all the plutonium and minor actinides they produce. As a result, nonfissile isotopes of plutonium build up, along with significant quantities of other minor actinides.