Presentation on theme: "Improvements in Liquid Effluents Greg Jones, Radiochemist R.E. Ginna Nuclear Station Ontario, New York."— Presentation transcript:
Improvements in Liquid Effluents Greg Jones, Radiochemist R.E. Ginna Nuclear Station Ontario, New York
Overview Ginna Station discovered several problems in liquid waste processing in 2001/2002 through our corrective action process. A Self-assessment of liquid effluents was performed at the request of the Chemistry Manager in February 2003. 2003 INPO E&A assigned an AFI to CY.6-1, “Degraded performance of the radwaste processing equipment resulted from insufficient oversight, control, and understanding of contaminant ingress pathways.”
Historical performance Ginna had used total gallons processed and total Curies released as indicators of liquid waste processing system performance. We typically process around 2E5 gallons per year which is near the industry lowest. We typically released 10-20 mCi, (excluding tritium), which led to little dose consequence. However, EPRI TR-109441 showed that Ginna was near the bottom of the industry in gallons of waste processed per cubic foot of resin consumed.
Process improvements A Station-wide Water Management Committee was formed in 2003. Participants included Operations, Chemistry, Engineering, Radwaste, and Station Management. Responsibility for liquid waste processing was assigned to Chemistry Manager. Weaknesses identified in INPO E&A were addressed - leaks of service water and house heating steam to the Waste Holdup Tank were repaired, and Consumable Control procedure instructions for use of surfactants were clarified. This set us on the pathway to improvement.
Further Process improvements Error traps in operating procedures were found and corrected - one step had operators adjusting pH in the release tank prior t o Chemistry approval to release. This forced us to choose between releasing higher activity than desired, or reprocessing NaOH treated water. Maximizing available water storage capacity for Ops prior to a refueling outage was included in outage planning so that the Control Room would not have to force the release of inadequately treated water due to capacity issues.
Further Process improvements Engineering is establishing a pathway for release of low activity/high conductivity water. This will take a burden from service water and mop water off of the waste treatment system. GTS Duratek suggested an alternative which would be a second carbon bed for removal of organics prior to polymer addition for removal of colloids. Cost basis has been used by the Water Management Committee to push small leak repairs - we use a spreadsheet to calculate total cost of not repairing a service water leak.
Waste System Failure Events Three similar ACTION Reports (“Abnormal Condition Tracking Initiation Or Notification”), between 11/01 and 7/02. In each case the monthly business plan goal for liquid effluents was exceeded. In each case the failure was abrupt and occurred prior to expected depletion of the resin beds. Chemistry suspected surfactants as the cause. Lead Technician reported suds in the effluent and influent. Dose rates on vessels were inconsistent with spent beds. Ginna has had a history of excessive surfactant use.
Surfactant Effects on Resins GTS Duratek evaluated the Ginna system performance in August 2002. Minimization of surfactant use was recommended due to carbon bed consumption (3CF carbon per/gallon of surfactant), and changes in colloidal behavior. An Action Report regarding incorrect dilution of a surfactant led to an event investigation. Within that investigation it was determined that further evaluation of surfactants was needed. Ginna contracted with General Engineering Laboratories (GEL) to analyze one surfactant against our resin.
Surfactant analysis GEL found a factor of 10 less resin fouling effect than Ginna Chemistry had anticipated. So - resin surface fouling by surfactant was not the cause of the observed failures. GEL also analyzed spent resin and found that the anion resin was saturated with boron as expected. But the spent cation resin analysis by ICPMS indicated only 1% of its capacity had been used when it was discarded as spent. What happened to its DF?
Surfactant Analysis Chemistry purchased a Particle Charge Detector (PCD) - long overdue. We immediately began to better meter the polymer dose for colloid removal. We learned that colloidal activity varied between 0% and 60% of our activity. We determined that small quantities of nonionic surfactant dramatically changed the PCD titration.
Surfactant Analysis 0.01% surfactant led to a factor of five increase in polymer required to titrate waste water to the isoelectric endpoint. The effect varied linearly with surfactant concentration. We contacted BTG, Inc. - the vendor of the PCD, to verify our observations. They concluded that increased surfactant concentration leads to increased polymer demand, linearly up to 0.4% surfactant, exponentially beyond 0.4%
Failures at Ginna We had been using a fixed polymer dose that had worked in the past. Addition of surfactant in a batch would lead to colloidal breakthrough, which is consistent with the system failure in April 2002. That would explain high activity in effluent with low dose rates on beds, and little cation content on discarded resin. We now strictly control surfactant pathways to the waste treatment system. This was not the only failure mechanism we encountered.
Other Destructive Contaminants Service water - 300uS/cm water prematurely exhausts ion exchange resin. Ammonia and hydrazine in heating steam systems - small total volume involved Other organics - oils, consumable chemicals, pigeon excrement, all prematurely exhaust waste treatment system comoonents. Water Management Committee is pushing resolution on all of these.
Measured Improvement Liquid effluent milliCuries released were reduced a factor of 12 from 2002 to 2003. Gallons processed per cubic foot of removal media consumed, increased by a factor of 3 from 2002 to 2003. Since total water processed remained effectively constant from 2002 through 2003, this meant 1/3 as much solid radwaste generated by the process. Waste influent conductivity has not changed, indicating that we still process too much non-radioactive water.
3 Points Minimize use of surfactants - even if compensated for by excess polymer, this is an unnecessary burden on the system. Minimize pathways for other contaminants to the liquid waste treatment system, or process them in a separate system. Never be satisfied with “good enough” past performance.