Nuclear Reactor Seismic Restraint with Core Retention Cooling

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Nuclear reactors with integral PWR designs face challenges in supporting the reactor core due to a high center-of-gravity configuration and lack of structural support from large-diameter piping, which can compromise stability during seismic events and loss of coolant accidents.

Innovation Solution

A support configuration using three spaced-apart support engagement surfaces and a bottom seismic support system with a vertically oriented pin and pin socket, along with a reactor core retention cooling system, to provide lateral and vertical seismic restraints while allowing for thermal expansion and minimizing contact with the reactor pressure vessel.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a high center-of-gravity configuration is used in integral PWR designs, then the reactor structure is compact and simplified, but lateral stability during seismic events deteriorates due to increased pendulum motion tendency

Engineering Contradiction:

Improvereactor structure complexityVSAvoidlateral stability during seismic events

Core Design Contradiction:

Device complexityVSStability of the object's composition

Solution Approach 1:

The support system is segmented into multiple discrete support points (at least two support points spaced apart) rather than a single centralized support. This segmentation distributes the stabilizing force across multiple locations, effectively counteracting the pendulum motion tendency caused by the high center of gravity while maintaining the compact integral PWR design.

Inventive Principle:

Principle #1Segmentation

2Stability of the object's composition

If traditional seismic support systems with extensive contact are used, then lateral seismic restraint is improved, but thermal expansion accommodation deteriorates due to increased mechanical constraint

Engineering Contradiction:

Improvelateral seismic restraintVSAvoidthermal expansion accommodation

Core Design Contradiction:

Stability of the object's compositionVSAdaptability or versatility

Solution Approach 1:

The invention extracts and removes the problematic extensive mechanical contact between the support system and the reactor pressure vessel. By using minimal contact points (at least two discrete support points) rather than continuous contact, the system provides adequate lateral seismic restraint while eliminating the thermal expansion constraint problem. The support points are positioned to engage only necessary structural elements.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The support system applies localized support only at specific discrete points rather than distributed contact. Each support point is strategically positioned to provide lateral restraint where needed while leaving other areas free for thermal expansion. The support engagement is localized to specific structural features of the pressure vessel.

Inventive Principle:

Principle #3Local quality

3Stability of the object's composition

If multiple discrete support points are used to prevent pendulum motion, then lateral seismic stability is improved, but device complexity increases due to additional support components

Engineering Contradiction:

Improvependulum motion preventionVSAvoidsupport system components

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The support points are designed to perform multiple functions simultaneously: providing lateral seismic restraint, accommodating thermal expansion, and supporting the reactor pressure vessel weight. By making each support point multi-functional rather than having separate systems for each function, the overall device complexity is minimized while achieving the desired pendulum motion prevention.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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

This configuration ensures stable reactor support, prevents pendulum motion during seismic events, and maintains reactor core cooling functionality during accidents, while accommodating thermal expansion and reducing the risk of structural damage.

Implementation Method 1

a reactor core retention cooling system that provides external cooling of the lower head of the reactor pressure vessel during loss of coolant accidents

Methodology Applied

Scientific EffectHeat transfer: Conduction (thermal)

Implementation Method 2

thermal insulation jacketing the lower portion of the reactor pressure vessel including the lower vessel head

Methodology Applied

Scientific EffectThermal insulation: Thermal Insulation

Data Source

PatentUS10825571B2Nuclear reactor support and seismic restraint with core retention cooling features

Publication Date: 2020.11.03 BWXT MPOWER INC

AI summary

A nuclear island includes a nuclear reactor, a lateral seismic restraint, and a reactor core retention cooling system. The lateral seismic restraint includes a vertically oriented pin attached to one of the bottom of the lower vessel head and the floor underneath the nuclear reactor, and a mating pin socket is attached to the other of the bottom of the lower vessel head and the floor. The reactor core retention cooling system includes one or more baffles, optionally thermally insulating material, disposed alongside the exterior surface of a lower portion of the reactor pressure vessel including at least the lower vessel head. A plenum is defined between the one or more baffles and the exterior surface of a lower portion of the reactor pressure vessel. The one or more baffles may define a lower plenum inlet surrounding the lateral seismic restraint.