Seabrook generators to breathe new life into Salem Unit-1
By Regina Carter and Linda Leech, Framatome Technologies
Last spring at Salem-1, Public Service Electric & Gas (PSE&G) discovered unexpected steam gen er ator (SG) problems beyond anything it had anticipated. After the situation was assessed, it became clear that if the generators were not replaced, the plant could not restart. “There were no viable repair options at that time,” said Eric Salowitz, PSE&G`s nu clear support director. “We were in full outage, and the generators had deteriorated beyond the point of repair with the technology available. The choices were either replace the SGs or ultimately decommission the plant. We could not afford to wait years while new generators were fabricated.”
What followed were measures, not of desperation, but of examining and facing cold, hard facts and deliberately moving forward to retain an important asset in the PSE&G business structure. Ex isting SGs in uncompleted plants ac ross the country were evaluated, with the North Atlantic Energy Service Corp.`s Sea brook Unit-2 the most likely candidate. The Seabrook plant had Westinghouse F-Series generators, the best match to the existing Westinghouse Model-51s in Salem, N.J. The decision to use the Seabrook SGs was made in a matter of weeks, and planning for the operation began.
Since no one had ever undertaken an SG replacement project using existing, older–but unused–generators, PSE&G felt that a cross-functional team was the best approach to tackling the monumental task at hand: removing the four, 350-ton SGs from Seabrook, shipping them to Salem, modifying the SGs to ensure compatibility with existing piping systems, adding a number of performance and maintenance enhancement features to bring the technology forward 20 years, installing the generators and licensing them for service.
Framatome Technologies (FTI) was selected as the prime contractor to coordinate the effort between the vendors and the customer and to do the preparation and modification work, as well as the final welding and licensing. Raytheon Nuclear would remove the Seabrook units and set them at Salem, and BIGGE, a heavy rigging company, would transport the giant components over land and sea to their new location.
To meet the American Society of Mechanical Engineers Section III code, the SGs had to pass a full hydro test. Typically, hydro testing is done at the manufacturing plant before the units are shipped, but this had not been done for the Seabrook components; therefore, the test was performed at the Seabrook site before the units were shipped to Salem. Hemispherical caps were welded onto the primary and secondary nozzles, and small penetrations were plugged. Then, water pressure in each generator was increased 1.25 times that of the operating pressure to find any leak paths. Successful completion of the test gave the project the green light.
The next big hurdle was removing and transporting both old and new generators–the old SGs, to Barnwell, S.C., for burial and the new, to Salem, N.J., over land and sea.
At both plants, the polar cranes were modified to lift the generators. Special barges were prepared, routes mapped across approximately 7 miles of land, and storm systems were carefully watched in preparation to transport the new generators from New Hampshire to New Jersey. Roads and bridges were modified to meet the demand of the heavy loads, including moving power lines, trimming trees, re-routing traffic, and improving bumpers on bridges and barge slips. Land transport took place late at night, with traffic re-routed by the state police. The generators were transported two by two on a staggered departure schedule from Hampton Harbor, N.H., to the Delaware River near Salem in about three weeks. Both land and sea transport of each of the 350-ton generators went off without a hitch. The new generators arrived safely at Salem three and one-half months after crews entered Sea brook Unit-2 to begin work.
The SGs required intensive modification because of the differences in size, design features and performance between the two sets of generators` components. Modifications included installing three new instrument nozzles (taps), or water-level indicators, per SG. Four new inspection ports were machined in, and a concentric phonographic-type finish was applied to existing ports to improve the sealing surfaces. In addition, the feedwater ring carbon-steel J nozzles (29 per SG) were replaced with Alloy 600 nozzles for enhanced resistance to corrosion and erosion.
Two temporary tent-like structures were erected at Salem where the new generators were modified to enable fitup. Nozzle ends were beveled using computer-controlled machines that allow machining to 0.0005-of-an-inch, so the SGs would mate exactly to the primary piping. Final connections are made with a high-precision narrow-groove welding technique.
The required feedwater nozzle modification on all four SGs will prevent thermal stratification by using a newly designed, integral thermal sleeve forging.
One unanticipated challenge the team faced was replacing the lateral and vertical supports in containment. The Model F Seabrook generators required an entirely different support structure, so a redesign was issued, and vendors were contracted to fabricate new supports for installation at Salem in parallel with the generators` modifications.
Behind the scenes
The licensing effort is simultaneously going forward to prove that the Seabrook generators are equal to, or better than, the SGs previously in Salem. Design-change packages are being prepared for all modifications, as well as for the installation. Chapters 5 and 15 of the “Final Safety Analysis Report” (FSAR) are being prepared for Nuclear Regulatory Commission review, including containment evaluation, FSAR accident evaluation, plant system evaluation, structural evaluation, and other design transients and controls analyses.
Daily challenges abound for team participants. Four companies have had to integrate different working organizations and operating styles to accomplish the task. But of all the challenges facing the project, the biggest is the extremely aggressive schedule.
“A lot of planning is done on the fly,” said Allen Chipley, FTI`s project coordinator. “There simply isn`t time to sit and mull over options. The team has to pull together to resolve issues as quickly as they arise and move the project forward.”
“The working teams are strong,” said Bob Penn, FTI machining manager. “At no time do you ever hear anyone say, `It`s not my problem.`” “We have four companies that have worked very well together to handle problems and pitfalls,” Salowit¥said. “The project is moving forward, and obstacles are being overcome.” z
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The old SG is ready to be moved onto a transportation vehicle that will carry it to Barnwell, S.C., for burial. Photo courtesy of FTI.
Adjustments were made (top) to the Wachs Split-Lathe system during beveling operations on the main steam nozzle. Photo courtesy of FTI.
The replacement SG, secured on land-transport, (left) exits the equipment hatch at Seabrook. Photo courtesy of Raytheon Nuclear.