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Tracking the Source of I-131 in the Cape Fear River. Greg Barley Supervisor-Chemistry Services. “You take all the experience and judgment of (men) over 50 out of the world and there wouldn't be enough left to run it.” Henry Ford. Background Information.
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Tracking the Source of I-131 in the Cape Fear River Greg Barley Supervisor-Chemistry Services
“You take all the experience and judgment of (men) over 50 out of the world and there wouldn't be enough left to run it.” Henry Ford
Background Information • Shearon Harris Nuclear Plant 900 MWe Westinghouse PWR • Liquid effluents discharge to Harris Lake via cooling tower blowdown line • Harris Lake discharges (ultimately) to Cape Fear River
Background Information (Cont’d) • Water composite sample collected upriver where Deep River and Haw River form the Cape Fear River (control location) • Water composite sample collected downriver at water treatment plant for town of Lillington (indicator location)
History • Medical applications result in environmental releases of I-131 from municipal sewage treatment facilities • City of Durham, NC, sewage treatment discharges to Haw River (tributary to Cape Fear River) • Prior to March 2006 there were a few events where I-131 was detected at the control location, but the indicator location showed <MDA
Problem Description • March 2006, I-131 detected at both indicator and control locations on the Cape Fear River • Similar concentrations observed at both locations • No discharge from Harris Lake occurring (low rainfall) • Water samples from Harris Lake showed <MDA for I-131 • Low rainfall reducing dilution water to Cape Fear River
Key Point #1 • I-131 NOT result of plant operation • I-131 present at both indicator and control locations at similar concentrations • No discharge from Harris Lake to Cape Fear River • No detectable I-131 in Harris Lake
Key Point #2 • Impact on the Radiological Environmental Monitoring Program • Identify source • Determine if program modifications are warranted
Key Point #3 • Communication, Public Relations • Detectable I-131 in public drinking water supply (Lillington) • Meeting held with NC Dept of Radiation Protection • Source is not plant operation • NC evaluate public impact • Communicate plan to identify source • Receive information from state personnel on potential sources • Critical in light of recent industry events regarding groundwater communication
Source Identification • Sample Tributaries • Haw River (Jordan Lake Dam), Deep River • Special sampling required special safety precautions • Where sampling was visible to public, informed local rangers (Jordan Lake Dam) • Special grab samples from control and indicator locations • Monitor the trend via “snapshots”
Observations • Source of I-131 is upriver of Jordan Lake along Haw River, likely Durham sewage treatment facility • Integrated concentrations at control and indicator locations very similar due to low dilution (dry weather, low river flow)
Conclusion #1 • No need to change REMP control location • Want to retain current control location in event I-131 detected at indicator location in future • Since infrequent occurrence, no new control location required
Conclusion #2 • Add enhancements to REMP • When I-131 detected at indicator location • Consider special sampling • Initiate lower I-131 MDA for Harris Lake Spillway water sample analyses • Revise procedure to require compensatory grab sampling when composite sampler is out of service
Conclusion #3 • Communication with regulatory officials is of tremendous importance • Information sharing two ways • Regulatory officials able to respond to public inquiries • Creates good will between licensee and regulators • Huge success!
