Radioactive air emissions program notice of construction, rotary mode core-sampling truck and exhauster.

摘要

Efforts have been ongoing to obtain core samples from the contents of each of the Hanford Site's 149 single-shell tanks (SSTs). The SSTs contain various amounts and combinations of liquid, sludge, and saltcake. Existing sampling equipment is unable to retrieve samples of hardened waste within established tank safety restrictions (particularly limits on temperature). A new rotary mode core-sampling system has been designed to sample tanks containing hardened wastes. The prominent feature of this new system is the use of a nitrogen gas purge. The nitrogen gas purge will cool the drill bit and prevent cross contamination of different waste layers in the tank. The nitrogen gas purge will also allow more complete sample recovery, by clearing cuttings that might otherwise obstruct the sampler or drill bit. Nitrogen was chosen over other compressed gases for its inherent safety. Many of the tanks to be sampled with the rotary mode core-sampling system are not actively ventilated, these tanks are operated at atmospheric pressure with passive (breather) high-efficiency particulate air (HEPA) filters. Unless a ventilation system of the proper capacity is used, addition of the nitrogen purge gas to SSTs will cause the tanks to pressurize. Additionally, the use of the rotary mode core-sampling system will generate aerosols and dusts potentially containing radioactive particles in the tank vapor space. Consequently, an exhauster will be required during operation of the rotary mode core-sampling system on SSTs to prevent tank pressurization and to control emissions. This exhauster will be required to be moved from tank farm to tank farm with the rotary mode core-sampling system.