Radiological Instrumentation Assessment for King County Wastewater Treatment Division

Strom, Daniel J. ; McConn, Ronald J. ; Brodzinski, Ronald L.

Pacific Northwest National Laboratory (U.S.)

关键词: Radiation Monitors;    Sewage Treatment Plant;    Cobalt-60;    Radioactive Materials;    Homeland Security;   

DOI  :  10.2172/935618
RP-ID  :  PNNL-15163 Vol. 2
RP-ID  :  AC05-76RL01830
RP-ID  :  935618

美国|英语

来源: UNT Digital Library

【 摘 要 】

The King County Wastewater Treatment Division (WTD) have concern about the aftermath of a radiological dispersion event (RDE) leading to the introduction of significant quantities of radioactive material into its combined sanitary and storm sewer system. Radioactive material could come from the use of a radiological dispersion device (RDD). RDDs include "dirty bombs" that are not nuclear detonations but are explosives designed to spread radioactive material. Radioactive material also could come from deliberate introduction or dispersion of radioactive material into the environment, including waterways and water supply systems. Volume 2 of PNNL-15163 assesses the radiological instrumentation needs for detection of radiological or nuclear terrorism, in support of decisions to treat contaminated wastewater or to bypass the West Point Treatment Plant (WPTP), and in support of radiation protection of the workforce, the public, and the infrastructure of the WPTP. Fixed radiation detection instrumentation should be deployed in a defense-in-depth system that provides 1) early warning of significant radioactive material on the way to the WPTP, including identification of the radionuclide(s) and estimates of the soluble concentrations, with a floating detector located in the wet well at the Interbay Pump Station and telemetered via the internet to all authorized locations; 2) monitoring at strategic locations within the plant, including 2a) the pipe beyond the hydraulic ram in the bar screen room; 2b) above the collection funnels in the fine grit facility; 2c) in the sampling tank in the raw sewage pump room; and 2d) downstream of the concentration facilities that produce 6% blended and concentrated biosolids. Engineering challenges exist for these applications. It is necessary to deploy both ultra-sensitive detectors to provide early warning and identification and detectors capable of functioning in high-dose rate environments that are likely under some scenarios, capable of functioning from 10 microrems per hour (background) up to 1000 rems per hour. Software supporting fixed spectroscopic detectors is needed to provide prompt, reliable, and simple interpretations of spectroscopic outputs that are of use to operators and decision-makers. Software to provide scientists and homeland security personnel with sufficient technical detail for identification, quantification, waste management decisions, and for the inevitable forensic and attribution needs must be developed. Computational modeling using MCNP software has demonstrated that useful detection capabilities can be deployed. In particular, any of the isotopes examined can be detected at levels between 0.01 and 0.1 μCi per gallon. General purpose instruments that can be used to determine the nature and extent of radioactive contamination and measure radiation levels for purposes of protecting personnel and members of the public should be available. One or more portable radioisotope identifiers (RIIDs) should be available to WTD personnel. Small, portable battery-powered personal radiation monitors should be widely available WTD personnel. The personal monitors can be used for personal and group radiation protection decisions, and to alert management to the need to get expert backup. All considerations of radiological instrumentation require considerations of training and periodic retraining of personnel, as well as periodic calibration and maintenance of instruments. Routine “innocent” alarms will occur due to medical radionuclides that are legally discharged into sanitary sewers on a daily basis.