Only particles of about 10cm or above can be tracked using radar. But both explosions would have generated millions of smaller fragments which are difficult to detect. The space station has shields to protect it against objects under 1cm in size. Anything larger than 1cm would be perfectly capable of penetrating these shields.
UK researchers have developed a device to drag space junk out of orbit. They plan to launch a demonstration of their "CubeSail" next year. It is a small satellite cube that deploys a thin, 25-sq-m plastic sheet.