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Chemistry Opportunities in Decommissioning. David A. Montt, CHP Sherman the resident bald eagle at Yankee Rowe Associate & Senior Health Physicist Dade Moeller and Associates, Inc. 1 Acton Place, Suite 201 Acton, Massachusetts 01720.
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Chemistry Opportunities in Decommissioning David A. Montt, CHP Sherman the resident bald eagle at Yankee Rowe Associate & Senior Health Physicist Dade Moeller and Associates, Inc. 1 Acton Place, Suite 201 Acton, Massachusetts 01720
Chemistry Opportunities in Decommissioning YNPS History • Achieved Initial Criticality—1960 • Began Commercial Operation—1961 • Upgrade to 600 MWt—1963 • Decision to Cease Operations—2/1992 • Possession Only Status—8/1992 • Decommissioning Activities—1992 - 2006 • Fuel Movement to ISFSI (Begin)—6/2002 • Fuel Movement to ISFSI Completed—6/2003 • Decommissioning Complete---10/2006 • ISFSI & GW Monitoring Continue to Present
Chemistry Opportunities in Decommissioning • http://www.yankeerowe.com/decommissioning_dismantle.html - web page forvideo of demolition progression from March 2003 to December 2003
Chemistry Opportunities in Decommissioning • Decommissioning Presents Creative Problem Solving Opportunities for Chemistry in Controlling Effluents • Examples Follow and Include: • Determining the Best Method to Monitor Potential Radioactive Effluents FromA PCB Thermal Desorption Unit • Determining the Feasibility of Tritium Remediation in Concrete Using High Heat • Optimizing FSS Sample Throughput While Implementing MARLAP Protocols • Optimizing Flexibility in Processing and Discharging Contaminated Water in a Rapidly Changing Environment
Chemistry Opportunities in Decommissioning • Effluent Monitoring for a Thermal Desorption Unit • History • The Exterior of the Vapor Container (white ball) had been painted with a custom paint made with PCB oil to maximize its ability to move with the steel as it expanded and contracted with temperature changes • Over time, with exposure to the sun, and temperature extremes ranging from -15’F and +105 ‘F during 30+ years, the paint matrix started to physically degrade, releasing PCB oil, and PCB paint chips to the environment under the VC, in storm drains and in Sherman Pond sediment. • These PCBs were discovered in 2001, and remaining PCB’s on the Ball were fixed by painting over the contaminated paint on the Ball to contain the source. • Initially, with an established remediation level of 2 ppm in soil in Massachusetts, the site was looking at having to ship about 25% of the surface soil in the industrial area off site. • With a newly imposed limit of 1 ppm in 2003, the amount of soil involved in remediation tripled (increased by 300%). • Remediation Method Chosen • Shipping soil off site is now cost prohibitive • Methods to remediate soil on site and re-use as fill are searched for and explored. • Thermal Desorption is the Method chosen
Chemistry Opportunities in Decommissioning • System Description • Processing Rate was Impressive • The Unit took soil feed in batches • Samples were taken at predetermined rates (1 sample per cubic yards) at feed and processed soil ends. • Remediated soil was consistently < 1.0 ppm PCB • Soil was run through the system by auger, heated to 725 degrees, volatizing the PCB, which was subsequently condensed and captured in a vessel for recovery/disposal.
Chemistry Opportunities in Decommissioning • System Description (cont.) • Driving of PCBs also drove off moisture content • Soil was also contaminated with licensed material gamma emitters (Co 60, Cs 137, Ag 108m, etc.) and Tritium • The unit temperature was too low to be concerned with metal volatilization, but moisture was driven off, captured by condensation, and re-used to re-hydrate the soil.
Chemistry Opportunities in Decommissioning • System Description (cont.) • The Oven/Auger discharge contained a bag house to capture soil • The raw condensate was captured, the PCB oil separated from the water, the water was then channeled to a particulate then charcoal filter • Any radioactive effluents present would also show up in the raw condensate • This is what was sampled, vs. using a stack monitor, to check for efffluents.
Chemistry Opportunities in Decommissioning • Monitoring Results • On a few occasions early in the process, tritium was identified at ~1800 pci/L. • Tritium levels dropped in the following three samples collected every 2 days. • Levels were then non-detect though the rest of the operation which continued for ~ 9 months. • Water was never discharged, as it was continually re-used to hydrate the soil. In fact water had ot be added to the system. • The company who owned the technology had a Massachusetts permit allowing them to dicharge up to 0.5 ppm PCB in water. • Yankee’s limit for PCB in water discharges was non-detect.
Chemistry Opportunities in Decommissioning • Monitoring Results (cont.) • During system set up, assembly and operational testing, dust could occaisionally be observed leaving the stack, or the tower where the dry soil was he hydrated. • As a result of this, an air sampler was placed in the vicinity of the unit where predominant wind direction moved the dust. • No licensed material was detected on the particulate filters.
Chemistry Opportunities in Decommissioning Arial View of decommissioned site to show path of PCB’s Water ran off VC to local storm drains and traveled to Sherman Pond
Chemistry Opportunities in Decommissioning • Conclusions • No Radioactive Releases from this process were identified • Required good communication with vendor on a regular basis • Vendor routinely collected and delivered samples to Environmental and Chemistry for analysis, minimizing potential for missed effluent releases • Chemistry kept vendor appraised of results and implications, facilitating productive and cooperative relationship to the benefit of both • Process may be suitable for other types of remediation
Chemistry Opportunities in Decommissioning • Reactor Support Structure (RSS) Demolition presented some interesting challenges in meeting DCGL’s for concrete mandated by Massachusetts. • Extensive core sampling of RSS indicated minor levels of tritium and no C14. • Later and more extensive core sampling found higher levels of tritium, challenging the original plan to use significant tonnage of the RSS concrete (containing minimal levels of activation products), as back fill. • Levels as high as 500 pCi/g, avgeraging 120 pCi/g • State of MA mandated 12 pCi/g • Based on the tritium levels, most of the RSS concrete would not be available for use as fill.
Chemistry Opportunities in Decommissioning • Solution? • Someone suggested using the PCB Thermal desorption unit to process the concrete to drive the excess moisture and tritium as tritiated water from the concrete. • If concrete levels could be reduced to 10 pCi/g or less, concrete would be processed using this methodology • The concrete was typically 1” in average dimensions. It could be processed, at a slight additional cost, to 3/4” dimensions. • Chemistry was asked to evaluate this on a Thursday morning, and to provide results and conclusions by the following Monday morning, as contract was under negotiation for PCB remediation with vendor and decision on Tritium remediation had to be made that Monday.
Chemistry Opportunities in Decommissioning • The Evaluation and results • Vendor lab was contacted. • Oven was available at 300 degrees C (~572 degrees F). 2 hour retention time would be simulated. • Procedure and instructions were drafted up and emailed to the lab. • A courier deliver the RSS concrete samples that afternoon. • Test was conducted Friday and Saturday in vendor lab. Results from vendor lab were emailed out Saturday afternoon to Chemistry.
Chemistry Opportunities in Decommissioning • The Evaluation and results (cont.) • Chemistry evaluated results, and drafted a report for Monday Morning • Average tritium remaining was just over 10%. • Question on cost effectiveness of pulverizing to 1/4” dimension was raised. • Levels of 5-6% of original tritium concentration would have resulted in a go ahead. • Decision was made to not utilize this process. • Results of study follow. • RSS concrete was shipped to Utah for burial.
Chemistry Opportunities in Decommissioning • Water Processing and Discharge in Rapidly Changing Environment • Plant liquid wastes still had to be dispensed with. • In plant treatment would not be available for the duration of D&D • Trenches and open foundations were anticipated to fill with water and contain radioactivity • PCBs & RCRA 8 metals were also anticipated • Continuous discharges and batch discharges were expected • pH, sediment were also as potential problems in regards to discharging to Sherman Pond
Chemistry Opportunities in Decommissioning • Strategy • NPDES permit up for renewal and to include specifics for SFP discharge • Added construction dewatering category • Specified plant and portable skid treatment • EPA & MADEP approach was to focus on quality of water discharged, and pathways with contingencies to use alternate discharge pathways as D&D progressed.
Chemistry Opportunities in Decommissioning • Strategy (cont.) • ODCM concentrated on in plant systems, and was revised to include portable, temporary skids • Provision was added for continuous and batch discharges from trenches and foundations. • Added sampling using composite samplers and/or grab samples. • Contingencies for loss of composite samplers included hourly grab samples • Continuous sampling included three initial grab samples – if all three results were within a certain level of agreement, continuous discharge with hourly grabs was peermitted.
Chemistry Opportunities in Decommissioning • Results • For the most part, pH and sediment precluded direct discharge and required the use of temporary processing systems employing Baker Tanks • Radiological constituents were not limiting • Concrete dust and rubble were the source of pH and sediments challenges, and it was ubiquitous. • PCBs also mandated treatment in Baker Tank Systems. 0.5 micron particulate filters were the most effective tool for abating PCB Levels in water • RCRA 8 Metals were not limiting at discharging water with low levels was permissible, and was based on 57 cfs discharge rate from Sherman Dam. If this discharge rate was higher, metal levels could be higher in the effluent, but this flexibility was never necessary.
Chemistry Opportunities in Decommissioning • Operation • Demolition contractor rented and operated the water processing systems (basis for this) • YAEC provided analytical support, approved discharges, oversaw contractor • Outfalls 003 and 004 were primaries for temporary system discharge points • Processing tanks utilized 120 mesh pre-filter on tank 1, settling tank with recirculation capabilities in tank 2, with the capability for pH adjustment, followed by 1 micron, or 0.5 micron filtration (controlled PCBs and fine sediment) • Fine sediment affected color of the water, was a NPDES permit requirement, and required considerable reprocessing near the end of the project.
Chemistry Opportunities in Decommissioning • Water Processing Under the Vapor Container During Demolition • Presented challenges • As steel shell was removed, rain could enter the VC, flush out radionuclides and contaminate the concrete and ground below, increasing the level of remediation required. • In addition, the paint used to contain the older PCB laden paint, had to be stripped for cut lines to prevent formation of dioxins. • This introduced the potential for PCB contamination in the water, and expansion of affected site areas.
Chemistry Opportunities in Decommissioning • Water Processing Under the Vapor Container During Demolition • SOLUTION • The solution was a bermed area covered with an impervious barrier to contain the water under the VC • This water was processed through a temporary system located adjacent to the VC (wet side) and positioned to take advantage of gravity flow between tank 1 and tank 2. • Water capacity of the tanks was limiting at times as an EPA certified methodology was required for PCB analysis and RCRA 8 metals analysis and took one week from shipment of samples to receipt of results. • Heavy rains frequently challenged processing capability. • Drops of steel occasionally penetrated the barrier mandating repairs • In one very heavy storm, the berm failed and overflowed, resulting in an estimated loss of ~5000 gallons. ~3000 gallons were captured and pumped back into the berm after the berm was repaired. • Initially water in the berm had levels of PCBs at 2 ppm, and detectable cobalt and cesium. These dropped off as time progressed.
Chemistry Opportunities in Decommissioning • BENCH TESTS • Bench Testing was an invaluable tool during Decomissioning • Examples included pH testing prior to the SFP discharge • Tritium in RSS concrete to determine the validity of remediation using thermal desorption equipement • On site Tritium analysis recovery determination • Tritium swipe methodology development at the request of executive management • Estimating initial mixes of buffer or acid to adjust pH, and determine potential for wide swings and at which points when adjusting large volumes for discharge • To catch potential problems when changes in work scope were discovered but not communicated. Screen Well house intake pipe plugging methodology was a good example.
Chemistry Opportunities in Decommissioning • Screen Well House Plugging • Initially the plan was to plug the discharge line, pump out the water using direct discharge, and fill the pipe with concrete • For reasons still unclear (cost? schedule?), the decision was made to pump the concrete slurry directly into the SWH after the plug was placed by divers without pumping the water out first. • At the request of a conscientious project manager, Chemistry investigated the impact of this change in strategy. • The concrete vendor was contacted and a sample of the mix was obtained, with directions mixing ratios. • 2 gallons of water from the SWH were collected • The concrete was mixed and added to the SWH sample water in proportions based on the volume of water in the SWH and the volume of concrete to be added. • pH was monitored and recorded frequently until readings stabilized. • Initial readings climbed to 12.8 pH units, and stabilized to 12.2 – 12.3 standard units within the first hour. TSS levels, sampled every 15 minutes were high initially, but never exceeded the NPDES limits.
Chemistry Opportunities in Decommissioning • Solution • A report on the study was penned and widely distributed with recommendations from both Chemistry and the water processing lead. • It was recommended several Baker tanks be leased to permit processing of the water expeditiously, and to provide additional water processing capacity in the future for the increasing number of open pits and open foundations that were challenging the existing system. • The recommendation was not well received initially due to the costs and perceived schedule impacts. However, bench test results left little doubt of impact should recommendations not be implemented. • Following intense negotiations with the demolition contractor, 4 additional baker tanks with processing and recirculation capabilities were placed in service, and except on rare occasions, were fully utilized continuously.
Chemistry Opportunities in Decommissioning • FSS Sample Throughput Maximized • Initially, following movement of Chemistry Lab to a Trailer to support of the Primary Auxiliary Building (PAB) demolition, three HpGe’s were installed leaving a footprint for a 4th. • Based on counting times necessary to meet DCGL’s (30 min/sample) and implementation of MARLAP protocols, a though put of 100 samples per day could be processed • Understanding the necessity to dry samples, the current the methodology used to that point created a bottleneck.
Chemistry Opportunities in Decommissioning • FSS Sample Throughput Maximized (Cont.) • No one owned the Sample prep trailer at that point, so Chemistry took ownership realizing it needed to maintain full control to provide the service requirements of stakeholders. • 2 drying ovens capable of drying in open pans limited sample production to 70 samples in 24 hours. 2 additional ovens were procured as backup in the event of failures of the older ovens. • A method tried at Maine Yankee was tested and implemented at Yankee Atomic. • Samples were dried in plastic Marinellis in the ovens with the covers off at 130 degrees C. The melting limit was 150 degrees. Except for one occasion, this process worked well, permitting up to 112 samples to be prepped in a 24 hour period and meshed well with lab production.
Chemistry Opportunities in Decommissioning • Additional advantages to this methodology included: • Eliminating at least 2 handling steps, • 2 potential cross contamination opportunities • The need to weigh each marinelli and cover (the weights between batches did not vary by more than 1%) • The opportunity to introduce bar code scanning of samples for COC simplification through analysis • Elimination of large volumes of soil in the prep facility as the samples were sifted in the field for > 90% of the samples • Chemists who understood lab operations and prep operations worked both facilities alternatively. • Electric Sifter Carts were designed and successfully field tested, but never gained popularity. • In both the lab and prep facility, the move to self contained ductless hoods was implemented, greatly improving operations.
