Whicker J J, Rodgers J C, Lopez R C
Los Alamos National Laboratory, NM 87545, USA.
Health Phys. 1999 Sep;77(3):322-7. doi: 10.1097/00004032-199909000-00012.
Aerosol transport tubes are often used to draw aerosol from desirable sampling locations to nearby air sampling equipment that cannot be placed at that location. In many plutonium laboratories at Los Alamos National Laboratory, aerosol transport tubes are used to transport aerosol from the front of room ventilation exhaust registers to continuous air monitors (CAMs) that are mounted on nearby walls. Transport tubes are used because past guidance suggests that extraction of aerosol samples from exhaust locations provides the most sensitive and reliable detection under conditions where the rooms have unpredictable release locations and significant spatial variability in aerosol concentrations after releases, and where CAMs cannot be located in front of exhaust registers without blocking worker walkways. Despite designs to minimize particle loss in tubes, aerosol transport model predictions suggest losses occur lowering the sensitivity of CAMs to accidentally released plutonium aerosol. The goal of this study was to test the hypotheses that the reliability, speed, and sensitivity of aerosol detection would be equal whether the sample was extracted from the front of the exhaust register or from the wall location of CAMs. Polydisperse oil aerosols were released from multiple locations in two plutonium laboratories to simulate plutonium aerosol releases. Networked laser particle counters (LPCs) were positioned to simultaneously measure time-resolved aerosol concentrations at each exhaust register (representative of sampling with transport tubes) and at each wall-mounted CAM location (representative of sampling without transport tubes). Results showed no significant differences in detection reliability, speed, or sensitivity for LPCs positioned at exhaust locations when compared to LPCs positioned at the CAM wall location. Therefore, elimination of transport tubes would likely improve CAM performance.
气溶胶传输管常用于将气溶胶从理想的采样位置抽取到附近无法放置在该位置的空气采样设备中。在洛斯阿拉莫斯国家实验室的许多钚实验室中，气溶胶传输管用于将气溶胶从房间通风排气口前端传输到安装在附近墙壁上的连续空气监测器（CAM）。使用传输管是因为过去的指导意见表明，在房间释放位置不可预测且释放后气溶胶浓度存在显著空间变异性，以及CAM无法放置在排气口前方而不阻塞工作人员通道的情况下，从排气位置提取气溶胶样本能提供最灵敏可靠的检测。尽管设计了尽量减少传输管中颗粒损失的方案，但气溶胶传输模型预测表明仍会有损失，从而降低了CAM对意外释放的钚气溶胶的灵敏度。本研究的目的是检验以下假设：无论样本是从排气口前端还是从CAM的墙壁位置提取，气溶胶检测的可靠性、速度和灵敏度都是相等的。在两个钚实验室的多个位置释放多分散油气溶胶，以模拟钚气溶胶的释放。联网的激光粒子计数器（LPC）被放置在相应位置，以同时测量每个排气口（代表使用传输管采样）和每个壁挂式CAM位置（代表不使用传输管采样）的时间分辨气溶胶浓度。结果表明，与位于CAM墙壁位置的LPC相比，位于排气位置的LPC在检测可靠性、速度或灵敏度方面没有显著差异。因此，取消传输管可能会提高CAM的性能。
