WHEN AN accident caused a reactor core meltdown at the Three Mile Island plant in Pennsylvania in the early-morning hours of March 28, 1979, the information reaching the public was fragmentary and contradictory. Even the leaders of the U.S. Nuclear Regulatory Commission were confused, and its chairman said two days later that he and the governor of Pennsylvania were "like a couple of blind men staggering around making decisions." When the Chernobyl nuclear power plant in the Soviet Union exploded in 1986, the grim early details were covered up even as radioactive clouds drifted from Ukraine to Sweden.

With this history, a healthy skepticism is in order when it comes to nuclear accidents anywhere. Recently, a radioactive spike was detected in the atmosphere over parts of Europe. No one has revealed what caused it, and it does not appear to be dangerous to human health. But already Russia has gone from denial to admitting the existence of high radioactive readings near a major plant for reprocessing spent nuclear fuel, raising concerns that something is amiss.

In late September and early October, French authorities monitoring the atmosphere discovered the presence of trace amounts of a radioisotope, ruthenium-106, a byproduct of nuclear reprocessing that is not normally present in the air. Germany found the same, as did at least a dozen other European countries; Romania found the highest levels. After consulting with technical organizations in Europe and running simulations and models, the French said the "simulations show that the most probable origin of this release is the southern Urals" of Russia, "without it being possible to be any more precise."

The French added that the release probably happened in late September and that the amounts suggest "this release could be the result of an accident" of some kind, although not a nuclear reactor accident, which would have released many other isotopes as well. This pointed to a reprocessing accident and release. Reprocessing nuclear fuel involves breaking it down into individual isotopes. But Russia denied being the source on Oct. 11, saying in a statement reported by its Sputnik news service that the radiation level around its facilities "is within normal levels." As it turned out, this was not true.

Russia acknowledged Nov. 21 that it had detected a significant radiation spike at two weather stations where the ruthenium-106 levels were 986 and 440 times higher than a month earlier. The stations are within a 62-mile radius of a Soviet-era nuclear reprocessing and isotope production facility at Mayak, in the Chelyabinsk region, on the eastern side of the southern Ural Mountains. Russia said there has been no accident at Mayak.

In the Chernobyl disaster, the dangers of official secrecy and lies were exposed to the Soviet people and to the world. Has anything changed? Chernobyl propelled Mikhail Gorbachev to launch his reforms of glasnost, or openness. That was three decades ago. Today, President Vladimir Putin's model of authoritarianism thrives on deception and coverup. If there was a nuclear reprocessing accident in September, let's hear the truth, and soon.