Well before the announcement of the proposed joint venture between the nuclear businesses of Framatome and Siemens, Framatome Technologies Group (FTG), approached Siemens Power Corporation in Richland, WA about working together to chemically clean the steam generators at Entergy's Waterford Nuclear Unit - 3.
       FTG already had a contract with Entergy to provide steam generator (SG) services at Waterford, and was prepared to perform a low-temperature chemical cleaning that was deemed necessary during evaluations performed in 1998. During the 16 years that the Waterford steam generators had been in operation, periodic sludge lancing had been performed, the most recent being three years ago. With the chemical cleaning, Waterford hoped to mitigate or prevent potential tube corrosion phenomena that had occurred at plants with similar steam generators, and to increase SG longevity and integrity. The Siemens process was chosen when Entergy made the decision to shorten its fall refueling outage to 30 days, if possible, but to no more than 35 days.
       Traditionally, FTG and other service providers in the US use a chemical cleaning process developed by the Electric Power Research Institute's Steam Generator Owners Group (EPRI/SGOG). This non-proprietary process performs chemical cleaning at less than 99°C (210°F). It is effective and has been extensively used in the US. However, due to the lower temperatures, the EPRI/ SGOG process takes longer to complete than the Siemens process. It was determined that the EPRI/ SGOG process could not meet the outage schedule at Waterford.
       The patented Siemens process operates at temperatures above 149°C (300°F). Waterford was aware of the Siemens process, even though it had never been used in the US. Given the time requirements of the outage, the Siemens process appeared to be the desirable choice. A feasibility study concluded that the Siemens process could meet the objectives specified by Waterford. A proposal was submitted in November 1999, and after joint negotiations, a contract was awarded to FTG/Siemens in January 2000 to perform an adaptation (qualification) study, application of the chemical cleaning, and waste processing during the refuel 10 outage in October 2000.

Preparation
To prepare for this historic first use of the Siemens process in the US, the ten months prior to the outage were used to write procedures, to perform the adaptation study, and to custom design the equipment to clean the two CE 3410 steam generators. In order to ensure that the process would run smoothly and safely on site, Siemens laboratories in Erlangen, Germany conducted six process and corrosion tests. These were independently verified by three additional tests performed by Dominion Engineering, Inc. at The Catholic University of America in Washington DC using their larger-volume special autoclave system.
       The outage was scheduled to begin on October 14, 2000. On June 6, six FTG personnel and the necessary equipment were mobilized for set-up. By September 19, all system set-up and checkout testing was completed. An additional seven Siemens and 21 FTG personnel and six tankers of process chemicals, provided by Waterford, arrived on site in early October. The tankers were connected to the High-Pressure Injection Pump (HPIP) system and the chemicals were pumped into the steam generators through a blowdown line connection in the auxiliary building.

The Siemens Process
The three-step cleaning process was initiated shortly after plant shutdown and utilized residual plant heat to achieve the temperature required for the iron step. The iron step was performed in series, first in SG-1 and then in SG-2. The copper step was run in parallel in both steam generators. Following a rinse step, both steam generators were drained. Sludge lancing was performed to remove any residue on the tubesheet of the generators. Measurements taken at the first egg crate support plate of each steam generator confirmed that actual corrosion was below defined allowances. The cleaning (from tubesheet wet to tubesheet dry) was completed in a total of 118 critical-path-time hours. The outage was completed in 34.5 days. Dr. John Remark, FTG Site Task Leader, commented at the conclusion of the cleaning that "in these times of increasingly shorter outages, this cleaning demonstrated the viability of the Siemens process."


Results
Approximately 5000 kilograms (11,000 pounds) of deposits were removed during the cleaning with 734,000 liters of liquid waste generated. Liquid waste was evaporated and distillate was released through a plant sump in compliance with plant discharge limits. Concentrates were sent for thermal destruction and disposal at a low-level radioactive waste-disposal site.
       Because this was the first time this process was used in the US, Framatome invited other customers to observe the process in action. Three US customers as well as representatives from Electricité de France (EDF) were on site during the cleaning process. Several have already indicated an interest for future use.
       Alexander Wolski, Director, Decontamination, Chemistry Services, Material Recycling at Siemens said, "This project demonstrated not only how well the technology works in US facilities but also the extraordinary compatibility of Siemens and Framatome."

Advantages of Siemens Chemical Cleaning Process

  • Less critical-path time required
  • Much lower person Rem exposure
  • Less liquid waste generated
  • No entry into containment building required
  • Less equipment
  • Faster set-up

 

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