THEY love to play no less than American children but get tired much quicker. "When they got off the plane, I was appalled," recalls Leonard Melnik, a Russian Orthodox priest from Portland, Ore., who helped bring these children to the United States. "They looked very pale, with big bluish pockets under the eyes."No wonder: Radiation is taking its toll. The 31 children who have just arrived for treatment at the Oregonian Health Society University (OHSU) are residents of Ukrainian cities and villages adjacent to the ill-fated Chernobyl nuclear plant. Aged seven to 14, they have lived for more than five years in a radiation environment created after the 1986 Chernobyl reactor explosion; doctors think they might develop leukemia. These Ukrainian children will spend about a month at OHSU. It is better than nothing, but may not help much. So they will return to their hometowns where there is a lack of any medicine at all. It's horrific when a nuclear accident happens in any country. It is much worse when it happens in a destitute state undergoing a severe crisis of identity, values, economy, and morale, which magnifies the disaster, transforming it into a irreparable tragedy. What make the Chernobyl disaster particularly bitter is that for too long, it was covered by thick layers of lies designed to protect the Soviet communist authorities. First, they tried not to say anything. For several days, the damaged reactor was spewing radiation into the air, and radioactive fallout was covering Ukrainian and Byelorussian cities and villages whose dwellers did not suspect they were getting dangerous doses. Their government did not alert them. LATER, when the radiation reached Sweden and a coverup was impossible, Mikhail Gorbachev told the world only 31 people had perished in the disaster. It sounded like the Kremlin leaders were sending the world the following message: A catastrophe? What catastrophe? A plane crash kills more than that." What is worse, the world has largely bought this hoax. Of course, some medical supplies were sent, some money collected. But the biggest nuclear disaster in history was soon forgotten like a medium-scale earthquake somewhere in the Himalayas. The difference is that earthquakes do not kill after they stop. Chernobyl's radiation continues to be lethal. Only now that Ukrainians have opted for independence does the truth surface. The Ukrainian Business Digest, a newsletter published in Westport, Conn., reports that the Health Ministry of Ukraine has revealed that about 1.8 million people (380,000 of them are children) live in the areas where an increased level of radiation was recorded. One Ukrainian nuclear physicist, Vladimir Chernousenko, says that 8 million to 10 million people live in heavily contaminated areas of Ukraine and Byelorussia, and that from 5,000 to 7,000 of those exposed to excessive doses of radiation have already died. However, this tragedy is very convenient for power-addicted Kremlin politicians: The agony of its victims is extended over years and does not get world attention. Meanwhile, the victims of Chernobyl have to lead an almost lonely struggle. The children that arrived in Oregon, for example, didn't have enough hard currency to pay for their trip from New York to Portland. Father Melnik had to put together an emergency rescue operation just to bring them to the West Coast. Foreign contributions to various Chernobyl relief funds have decreased to a trickle. Moscow has consistently refused to recognize the special needs of Ukraine: This year, prior to the vote for independence, Ukraine received from the central government of the USSR only 10 percent of the imported medicine originally asked for. So does the world care? Or does it not? SAC/TC Records, a company from Glen Ridge, N.J., has recently volunteered to organize charitable rock-music concerts in Kiev and Moscow to raise money for the victims of Chernobyl. Its managers talked a number of Japanese businesses into this venture. It's hoped that the charitable galas will materialize by August 1992. This effort will help, but not enough. Independent Ukraine has acquired a terrible burden of providing relief for millions of people suffering from the Soviet government's negligence, cowardice, and arrogance. It will do all it can to alleviate the pain. But it needs more help, and more compassion, in the face of human suffering.