The report points to problems with the handling of the crisis, including a difficult process for seeking compensation for radiation exposure, a lack of openness about health risks from radiation and inadequate protection for nuclear plant workers.
It urges Japan to improve its emergency preparedness and its handling of compensation claims.
The Geneva-based council is due to discuss the report, compiled after a visit to Japan by Grover late last year, at its general meeting starting Monday.
Japan's atomic energy industry remains in crisis more than two years after a powerful earthquake and tsunami triggered meltdowns in three reactors at the Fukushima Dai-Ichi nuclear plant.
The U.N. report cited a number of "serious challenges" and urged the government to involve affected communities in decisions and do more to protect and help vulnerable groups such as children, pregnant women, the disabled and the elderly.
That acquisition of a majority stake in the company "has arguably helped TEPCO to effectively avoid accountability and liability for damages," the U.N. report said.
The compensation should include financial relief to help the tens of thousands of residents displaced by the disaster rebuild their lives, it said.
So far, TEPCO has paid 2.3 trillion yen, about half of it to companies and business owners. That amount includes 1.6 million individual claims, mostly from voluntary evacuees. Because the amount of claims is expected to exceed the initial estimate of 3 trillion yen ($29 billion), the government has injected an additional 154 billion yen ($1.5 billion) into the compensation fund.
About 150 000 Fukushima residents are still displaced. Hundreds have filed claims seeking greater compensation, including many living outside the prefecture.