Reactor Vessel and Internals Training

Training Material Information

• Training Material Approval: Revision 1
• Training material number: PLLP-RPCT-251-02, Revision 3
• Training material title: Reactor Vessel and Internals
• Estimated completion time: 2 hours
• Type of training material: Lesson Plan, Qualification Document, Training Program Description, Lab Guide, Simulator Exercise Guide, Training Form, Familiarization Guide, Other, New Material, Minor Revision, Major Revision, Cancellation
• Superseded Material: PLLP-RPCT-221-03
• Reason for Revision: Updated material to the correct format and removed Entergy and fleet references
• Tracking Number: N/A
• Prepared by Kristin Jenerou on 02/06/2025
• Reviewed by Kenneth Morris on 2/7/2025
• Approved by Jamie Ellis on 2/24/2025

Reactor Vessel and Internals Training

• The training is a Palisades Basic System Review
• Also used for Radiation Protection Continuing Training
• The main goal of the training is to gain enhanced knowledge and understanding of the Reactor Vessel and Internals.

Course Objectives

• From memory, the importance of the Reactor Vessel and Internals to plant safety and radioactivity containment should be described per plant design documents
• From memory, be able to describe the Reactor Vessel and Internals System basic interrelationship with other plant systems in accordance with plant design documents
• Given a basic diagram, be able to locate the Reactor Vessel and Internals System’s major components in the plant in accordance with the plant’s as-built configuration
• Given a survey, be able to relate radiological hazards associated with major components in the system as documented in current Palisades radiological surveys

Reactor Vessel Major Components

• A vertical cylinder with hemispherical heads make up the reactor vessel major components
• The lower head is welded on with no penetrations
• The upper head is removable
• Internal components are supported by the Core Support Barrel

Primary Coolant Flowpath

• Coolant enters through 4 inlet nozzles
• It's directed downward in the annulus between the CSB and RV
• Flow is directed through the flow skirt at the bottom of the RV
• Coolant travels upward through the core
• Coolant exits through 2 outlet nozzles

Reactor Vessel Internals Design

• Designed to safely perform functions during steady-state and normal operating transients
• Safe shutdown capability during earthquake and major LOCA loading conditions is assured through limitations on stresses and deformations
• Support and alignment of internals are maintained under normal loads, earthquake plus pipe rupture loading

Control Rod Drive Mechanism (CRDM)

• CRDM nozzles (45) are connected to the RV head at flanges
• CRDM inserts or removes control rods during operation

CRDM Radiological Hazards

• Personnel Hatch Posted: RA CA
• Ctmt Posted: ARA AL2
• Top of Rx Head Posted: HRA HCA

Davis-Besse SOER 02-04

• A 24 in² cavity was discovered in the reactor head adjacent to # 3 CRDM nozzle
• Wastage from a through-wall crack removed 6-in base metal
• 1/4-in stainless steel cladding became the RCS pressure boundary
• A Leak went undetected and the potential for wastage was unrecognised

Incore Instrument

• Eight Incore Instrument nozzles penetrate the RV Head
• Cables are disconnected from connectors at flanges to support RV head removal

Core Support Barrel

• Carries entire weight of the core and core shroud
• Measures 150” ID, 1 inch wall thickness
• It is suspended by 4 inch thick flange from reactor vessel ledge
• Snubbers prevent flow vibration and seismic movement of the CSB
• Core support lugs (9) “catch" the CSB in the event of catastrophic failure

Flow Skirt

• Distributes flow in lower plenum
• Prevents vortices
• Provides equalized pressure distribution across bottom of CSB

Upper Guide Structure Assembly

• It Is a flanged grid structure of 45 Control Rod spacing shrouds
• Also includes a fuel assembly alignment plate
• This alignment plate has flow distribution holes
• Includes Incore Instrument guide tubing
• The UGS handled as one unit during installation and removal.

UGSLR Radiological Hazards

• UGSLR Laydown Area is Posted as HRA
• HCA and Level 3 Alpha

Operating Experience (CR-PLP-2015-04793)

• Problem: While observing work on the Upper Guide Structure Lift Rig (UGSLR) it was identified that workers were not wearing lapel air samplers
• Consequences: Failure to use a lapel air monitoring device reduces the ability to perform an evaluation of a potential intake of alpha radionuclides in the event a person has a problem with their equipment

Interfacing Systems

• Primary Coolant System
• Control Rod Drive System
• Incore Nuclear Instrumentation
• Radwaste System
• Reactor and Pressurizer Gas Vent

Primary Coolant System Interfacing

• Primary coolant enters the reactor vessel through the 4 inlet nozzles (cold legs) and exits through 2 outlet nozzles (hot legs)

Control Rod Drive System Interfacing

• The Control rod drive mechanism nozzles (45) penetrate the removable reactor head
• The CRDM housings are connected to the reactor vessel via the CRDM nozzles

Incore Instrumentation System Interfacing

• Eight (8) Incore Instrument nozzles penetrate the reactor vessel head
• The ICI nozzles are covered with bolted on blind flanges, which contain the individual instrument penetrations

Radwaste System Interfacing

• Drain path of leakage through the reactor vessel flange seals (2) is to the Primary Drain Tank or Containment Sump drains

Reactor and Pressurizer Gas Vent Interfacing

• Reactor Vessel head vents to the tilt pit, quench tank or containment/drain

Plant Safety and Radioactivity Containment

• The Reactor Vessel is the primary barrier preventing release of fission products to the atmosphere
• Containment and Fuel Cladding are also barriers

Summary Points

• Solicit questions
• Encourage students to fill out training feedback forms