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CECIL®

Effective systems for secondary side maintenance are essential to ensure long life for pressur-ized water reactor (PWR) steam generators. Corrosion products formed throughout the second-ary cycle settle on top of the tubesheet and promote degrada-tion of the tube bundle. Also, foreign objects introduced during initial fabrication or maintenance activities impinge on tubes dur-ing operation and can eventually wear through tube walls causing primary to secondary leakage.

Forced outages to repair tube leaks are very costly, typically last-ing 14 days and incurring costs of about $6 million. Ultimately, if enough tubes have been dam-aged and plugged, the steam gen-erator must be replaced. Includ-ing replacement power, this can cost over $300 million at some nuclear plants.

Until recently, it was difficult to address these problems effective-ly. Conventional sludge lancing (water spray) techniques do not remove all the corrosive sludge material that builds up on the tubesheet. Foreign object retrieval has been difficult in the annulus region and virtually impossible in the tube bundle. In addition, the radiation exposure associated with secondary side maintenance is high.

The need for equipment and systems that could access the tube bundle interior, remove sludge without damaging tubes, identify and remove foreign objects, and at the same time reduce personnel exposure to radiation was evident. In 1986, the Electric Power Re-search Institute (EPRI) cosponsored a research program with Consolidated Edison of New York, the Empire State Electric Energy Research Corporation (ESEERCO), and Public Service Electric and Gas (PSE&G). The result was Foster-Miller’s development of CECIL (Consolidated Edison Combined Inspection and Lancing system), a teleoperated robot specifically designed to provide superior secondary side maintenance capabilities.

CECIL 4 General Arrangement

The CECIL 4 Robot

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One HSL is for removing hard sludge deposits from the tube lane (10 gpm at 6000 lb/in.2). Another SSL is for removing soft sludge from the tube lanes and shadow zones between tube lanes (10 gpm at 2500 lb/in.2). The third DSL is configured to remove hard sludge from the tubes and tubesheet (10 gpm at about 6000 lb/in.2).

In addition to intertube lancing, CECIL provides conven-tional lancing with eight nozzles built into the robot body. These high volume, medium pressure barrel spray water jets (40 gpm at about 1500 lb/in.2) are directed down the blowdown lane to flush soft sludge and loos-ened debris from the tube bundle.

Water for CECIL cleaning operations is recycled by a sludge processing/pumping system to reduce waste water volume.

All CECIL activities are controlled from a remote worksta-tion and monitored with video cameras located inside the steam generator and on the handhole platform. Real-time graphics show the robot and lance positions in the generator at all times and all in-bundle images are stored on videotape for future reference. The control station is typically situated in a low radiation area on the operating level. Prior to the development of CECIL, no comparable equip-

ment existed for PWR steam generator secondary side maintenance and inspection. This ad-vanced system represents the application of leading edge technology to preserve steam generator life. The CECIL robot is remotely operated and can perform sec-ondary side visual inspections, soft and hard sludge removal, sludge sampling, and both in-bundle and annulus foreign object search and retrieval (FOSAR). The key to CECIL’s success is its ability to access the entire in-bundle area of the tubesheet.

The CECIL robot rides on a rail assembly installed through the open steam genera-tor inspection port. One end of the rail rests on a stand placed against the center stay rod and on top of the blowdown pipe; the other end is secured to the handhole flange. The robot can move longitudinally along the rail assembly and extend and retract a flexible lance, which can be driven down the narrow (approximately 0.3 in.) gaps between the columns of U-tubes. The robot also can rotate about its axis to position the lance at any point within the tube bundle above the tubesheet and below the first support plate.

The robot’s flex lances are the transport mechanism for delivering spray nozzles and a videoprobe deep into the tube bundle. There are three types of intertube lances.

CECIL 4 Control Station

Control Screen for CECIL 4

The system is continually evolving to expand CECIL’s capabilities. Most recently, CECIL-5 was modified to in-corporate foreign object search and retrieval. Two FOSAR systems were developed: in-bundle FOSAR to locate and retrieve objects trapped inside the tube bundle and an-nulus FOSAR for object removal from the annulus region between the tube bundle and steam generator wall.

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Both FOSAR systems are compatible with existing CECIL system technology and both use an adaptation of the lance to deliver grappling tools inside the generator. The in-bundle FOSAR lance has four tools available to retrieve objects of varying shapes and sizes from the narrow gap between tubes. The annulus FOSAR lance has a larger, stronger two-prong end effector, capable of removing bigger, heavier objects.

The CECIL-4 robot was field tested for the first time in 1989 at Indian Point 2. Results showed the system removed the same amount of sludge from one steam genera-tor as conventional lancing did from three other generators combined, while cutting personnel radiation exposure in half.

Since the initial field demonstration of the CECIL-3 prototype in 1987, CECIL systems have been used successfully to clean and inspect steam generators throughout the world. Sites include Consolidated Edison of New York (Indian Point 2, USA), Public Ser-vice Electric and Gas (Salem 1 and 2, USA), Northern States Power (Prairie Island 1, USA), Kansai Electric (Ohi 1 and 2, Mihama 2 and 3, Takahama 1 and 2, Japan), and SRA/Electricite de France (Bugey 4, France).

CECIL-5 was introduced in 1991 with the initial field test of the in-bundle FOSAR sys-tem at Salem 1. Three objects (a washer and two weld rod pieces) were successfully removed in a short period of time and no known objects remained inside the generator. Later that year, the first fully remote robotic retrieval of foreign objects from a steam generator an-nulus took place at Indian Point 2. This demonstration of annulus FOSAR removed five large objects, including

a pocket dosimeter. The reduction in personnel radiation exposure over conventional techniques was estimated at 70 percent.

Through agreements with Foster-Miller now QinetiQ North America TSG, the CECIL technology has been licensed for use in Japan by Mitsubishi Heavy Industries and in France and other selected European countries by

SRA/Electricite de France. In early 1993 Westinghouse Electric Corpora-tion licensed the CECIL technology for use in the United States.

While the CECIL robot was originally designed to inspect and clean West-inghouse Model 44 and Model 51 steam generators, design modifica-tions have now extended its applica-tions to Mitsubishi models 44 and 51 and Framatome 900MWe CPO and 1300MWe steam generators. Work is currently under way to extend the technology to other steam genera-tor designs and to develop additional tools for secondary side maintenance.

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