Owner/Operator: Pacific Gas & Electric Co.
Diablo Canyon Power Plant, which is situated in a postcard-perfect location on the central California coastline, generates electricity for more than three million households in central and northern California. In 2009 the project team at the dual-unit Westinghouse pressurized water reactor facility replaced four steam generators at Unit 1 in just 58 days. Through meticulous planning and excellent project execution, performance on this Unit 1 project was an improvement on the earlier Unit 2 steam generator replacement project.
Located on the dramatic Pacific coastline and encircled by green mountain ranges, Pacific Gas & Electric Co.’s (PG&E’s) Diablo Canyon Power Plant (DCPP) has a surrounding worthy of a five-star resort (Figure 1). But the project team at this facility definitely did not embrace a laid-back California attitude during their recent steam generator replacement project (SGRP). Instead, they set up an aggressive work schedule and replaced four steam generators in Unit 1 in record time with a superlative safety record.
1. Pacific powerhouse. The 2,300-MW Diablo Canyon Power Plant is located near Avila Beach in central California. The installation of eight generators in 2008 and 2009 was the largest project in the history of the plant since initial construction was completed in the 1980s. Courtesy: PG&E
Project Profile
The Steam Generating Team West (SGT), a URS Washington Division/AREVA NP joint venture company, provided services for replacing the four steam generators at Unit 1 during a planned refueling outage that began in January 2009 and was completed in 58 days.
Steam generators are replaced as part of a power plant’s long-term maintenance program. Inside the steam generators used in pressurized water reactor power plants, heated water that has passed through the reactor is pumped through thousands of small tubes. The heat is then transferred through the walls of the tubes to water in a separate system, which then boils and turns into steam. The energy in the steam is used to turn a turbine generator to generate electricity. The steam generators used at DCPP are each 70 feet long and weigh 350 tons.
Each of the two DCPP units produces 1,150 MW, and each unit was designed with four steam generators. SGT provided project management, planning, engineering, and construction services to prepare and install the four new steam generators. In 2008 the SGT team had successfully replaced the steam generators in Unit 2 during a scheduled refueling outage.
SGT’s scope of work included general design, safety analysis, licensing, old generator storage facility design and construction, construction of temporary facilities, removal of existing steam generator insulation, removal of existing steam generators, installation of replacement steam generators, supply and installation of new insulation, and restoration of the plant.
Safety: A Vital Concern
SGRPs pose a significant challenge to employee safety, as the work is performed in an operating facility with a large variety of potential physical and radiological hazards. These challenges include high-radiation areas, confined spaces, heavy rigging, and hot work in close quarters. Safety permeated all aspects of the team’s work, and each task was meticulously planned. SGT’s total workforce for the DCPP Unit 1 outage exceeded 1,100 manual and nonmanual personnel. The project achieved 1 million safe work hours on December 1, 2008, and 1.9 million safe hours through project demobilization in May 2009.
The project team finished under the radiation dose goal and in the top quartile industry performance for radiological exposure. This feat was accomplished while working in a 30% higher radiation dose field compared with the Unit 2 SGRP performance while achieving a radiation dose that was only 15% higher. The team was committed to keeping radiation exposure as low as reasonably achievable (ALARA) and employed innovative ideas to minimize the radiological exposure, such as additional shielding and work sequencing.
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sincerely
rafael guarecuco
venezuela