Sealed Cable Inlet With Bellows for Nuclear Containment
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Solution Overview
Problem
Existing sealed electric inputs for nuclear power plant containments, designed for single reinforced concrete walls, fail to effectively manage relative motion between external and internal walls due to seismic events and thermal expansion, leading to potential damage and insulation breaches when used in multi-layer containment systems.
Innovation Solution
A sealed cable input system featuring embedded connection pipes with bellows on both internal and external ends, supported by tapered bellows and twisted conical compression springs, allowing for horizontal and vertical movement compensation, and protected by concentric pipes to maintain insulation integrity during thermal and seismic displacements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sealed cable input system is used in multi-layer containment walls, then insulation integrity is maintained, but the system fails to accommodate relative wall motion during seismic events and thermal expansion
Solution Approach 1:
The cable input system incorporates dynamic elements including bellows that expand and contract, springs that compress and extend, and rollers that move along tracks. These dynamic components allow the sealed cable penetration to accommodate relative motion between internal and external containment walls during seismic events and thermal expansion while maintaining insulation integrity.
Solution Approach 2:
The bellows component is constructed as a flexible metallic structure with multiple expansions and contractions that allows axial movement of the cable while maintaining the sealed barrier. This flexible shell structure accommodates relative wall motion without compromising the insulation integrity of the penetration system.
2Reliability
If the cable is rigidly fixed at both ends, then insulation integrity is maintained, but the cable cannot accommodate thermal expansion and seismic displacement
Solution Approach 1:
The cable fixation system transitions from rigid fixed-end support to dynamic support mechanisms including springs that allow axial movement, bellows that accommodate length changes, and rollers that permit controlled displacement. These dynamic fixation methods maintain insulation integrity while allowing the cable to respond to thermal expansion and seismic displacement.
Solution Approach 2:
The system allows the cable's physical parameters (length, position, orientation) to change dynamically in response to thermal and seismic conditions. The spring constant, bellows expansion ratio, and roller position are designed to permit specific ranges of movement while maintaining the sealed barrier function.
3Adaptability or versatility
If compensation means with rollers are used, then relative motion is accommodated, but friction forces limit tensile load capacity
Solution Approach 1:
The bellows component provides a flexible sealed connection that accommodates axial movement without relying on rolling or sliding friction. This eliminates the friction force limitation present in roller-based compensation systems while maintaining the ability to compensate for relative wall motion during seismic events and thermal expansion.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enhances the reliability and durability of high-voltage electrical conductor connections by accommodating relative wall motions, maintaining insulation integrity and reducing maintenance needs, while protecting against thermal and water ingress.
Implementation Method 1
pipe installed inside the external wall in line with the connection pipe with bellows on the external end
Implementation Method 2
cable output is supported by internal surfaces of tapered bellows ends
Implementation Method 3
cable output is located on supports with a gap relating to the pipe internal surface
Data Source
AI summary
The invention relates to the field of electrical engineering, and specifically to sealed inlets of electrical circuits into a sealed area of a multi-layered containment shell of a nuclear power station. This design can be used in passages through an external and an internal wall which are subject to relative mutual displacement as a consequence of a seismic phenomenon or thermal expansion of the walls and passage. The problem addressed by the present invention is that of increasing the operating reliability of a sealed cable inlet when high-voltage electrical conductors which have little bending capacity are used. The problem addressed is achieved in that the sealed cable inlet through an external and an internal wall of a containment shell of a nuclear power station comprises an embedded pipe (3) which is arranged in the internal wall (1), with an inlet section (44) of a cable (2) fixed rigidly within said pipe. A means for compensating for a relative movement between the cable (2) and the external wall (11) is mounted in the external wall (11) coaxially with respect to the pipe (3). The compensating means has a tube (19) with a bellows (24) on the external end plane (20) and with a second analogous bellows (25) which is mounted symmetrically on the opposite end plane (21) of the tube (19) at the internal surface (18) of the external wall (11). The free ends (30) and (31) of the two bellows (24) and (25) are of conical design and have internal surfaces (28) and (29) which are support elements for an outlet section (46) of the cable (2), which is arranged freely in the tube (19) with a gap (47) relative to the internal surface (49) of the tube (19). The gap (47) between the braiding (48) along the external surface of the cable (2) and the internal surface (49) of the tube (19) is selected using a design calculation. The gap (47) must not be less than the value of maximum orthogonal thermo-seismic movement in one plane of the internal wall (1) relative to the external wall (11) and change in the coaxial position of the cable (2) in the tube (19).