A cold snap and resulting power-line failures forced the Chernobyl nuclear power plant in Ukraine to shut down yesterday, three weeks before it is due to be closed for good. While there were no reported radiation leaks, operators are considering simply keeping the plant turned off from here on out, rather than powering it up for the few days before the plant’s permanent closure. Cash-strapped Ukraine is shutting down Chernobyl, which provides 5 percent of the country’s electricity, only because Western nations have pledged funds to build new nuclear reactors elsewhere in the country.