Core shroud cracking repairs at Brunswick Unit 1 and Unit 2

Conference · Sun Dec 31 04:00:00 EST 1995

OSTI ID:234168

Smith, R E ^[1]; Bertz, S; Wilton, B ^[2]; Giannuzzi, A J ^[3]

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1. SciTech, Inc., Mooresville, NC (United States)
2. Carolina Power and Light, Southport, NC (United States). Brunswick Nuclear Plant
3. Structural Integrity Associates, San Jose, CA (United States)

Extensive circumferential cracking was identified in the weldments that join the upper and middle core shroud cylinders at Brunswick Unit 1. An extensive In-Vessel Visual Inspection (IVVI) had been performed in the summer of 1993 in response to the General Electric (GE) RICSIL NO. 54. This information letter identified core shroud cracking in the beltline region of a BWR 4 located outside the United States. The IVVI at Brunswick had been enhanced to improve sensitivity and assure that very tight cracks of the type found in the overseas BWR could be found if present. The purpose was to provide an effective characterization of the core shroud condition. A mechanical repair was developed for both Brunswick units that structurally links the upper shroud cylinder, top guide support ring, and the middle shroud cylinder. The design accommodates the stepped cylinder geometry and eliminates any reliance on the circumferential welds originally designed to join these components. The design was completed, the clamping devices fabricated, installation tooling designed and fabricated, and the clamps successfully installed in Unit 1 during the last quarter of 1993. Plans were established to preemptively apply the clamp repairs in Unit 2 after verifying the cracked condition of the top guide support ring welds, and after characterizing the condition of the rest of the shroud. These plans were carried out during the spring 1994 outage of Unit 2. This paper will present the basis and evolution of design, an overview of the analysis, development of the tooling, fabrication of the repair clamps, the installation process, and lessons learned.

• OSTI ID: 234168
• Report Number(s): CONF-9411168--; ISBN 0-87171-444-2
• Country of Publication: United States
• Language: English

Related Subjects

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
BRUNSWICK-1 REACTOR
BRUNSWICK-2 REACTOR
CRACK PROPAGATION
FASTENERS
INTERGRANULAR CORROSION
REACTOR COMPONENTS
REACTOR CORES
REPAIR
SHROUDS
SPECIFICATIONS
STAINLESS STEEL-304
STRESS CORROSION
WATER CHEMISTRY
WELDED JOINTS