Metal seals are also highly used in radiation environments such as nuclear plants. They can offer very high leak tightness up to 10-12 mbar.lit/sec. Generally spring energized metal seals are used in radiation resistant seals with Nimonic 90 as the spring and double/single jacket on top of it. The seals are well cleaned and packed to avoid contaminations. Most of the times the seals have a soft 2nd jacket which can flow in to the imperfections of groove and provide very high leak tightness. Also SS jacket and spring can be used in radiating environment but the performance of Inconel and Nimonic 90 has been much better.