BWR Reactor Vessel Modeling¶
Source
BWR Modeling Guidance — Vessel (preliminary draft, step 1 only); RPV structure inferred from component guidance for jet pumps, separators, CRD tubes, and recirculation lines.
Incomplete Source Guidance
The BWR Vessel section of the modeling guidance was in an early draft stage (step 1 of 4 in the review process) and has not been fully developed or reviewed by NRC technical staff. The information below is compiled from references made by other BWR component guidance sections that connect to the RPV VESSEL component. A complete vessel modeling guidance document is expected in future revisions.
Overview¶
The BWR reactor pressure vessel (RPV) is modeled as a 3D VESSEL component in TRACE. Unlike PWRs, the BWR vessel must accommodate in-vessel boiling, steam-water separation equipment, and the jet pump recirculation system. The VESSEL component is the central hub to which most other BWR components connect.
RPV Structure — Inferred from Component Guidance¶
Based on references in the jet pump, separator, CRD tube, and recirculation line guidance, the RPV VESSEL component uses:
Radial Rings¶
The RPV is typically divided into 2 radial rings plus a downcomer region:
- Ring 1 — Inner core region (subset of fuel assemblies)
- Ring 2 — Outer core region (remaining fuel assemblies)
- Downcomer — Annular region between core shroud and RPV wall
The allocation of fuel assemblies to rings determines NPIPES for CRGTs and NSEPS for separators.
Axial Levels¶
The RPV is divided into multiple axial levels. Based on CRD tube guidance (6 cells matching RPV levels 2–7) and separator guidance (standpipe/separator regions at levels 12–13), the RPV has at least 13 axial levels:
| Approximate Level | Region |
|---|---|
| 1 | Lower head / CRD housing penetrations |
| 2–7 | Lower plenum through core support (CRGTs span these levels) |
| 8 | Core inlet / fuel support piece |
| 9–11 | Active core region |
| 12 | Standpipe region (separator inlet) |
| 13 | Separator / upper plenum |
Azimuthal Sectors¶
The RPV typically uses 2 azimuthal sectors (180° each), which results in 4 separator SEPD components (2 rings × 2 sectors).
Key Connections¶
| Component | Connects To | RPV Location |
|---|---|---|
| Jet Pump | Main tube outlet → RPV lower plenum; side tube inlet ← riser | Downcomer / lower plenum |
| Steam Separators | Standpipe inlet ← RPV level 12; steam outlet → dryer region; liquid return → downcomer | Upper plenum / above core |
| CRD Tubes | Bottom ← lower head (leakage); top → core bypass (level 8–9 edge) | Lower plenum through core |
| Recirculation Lines | Suction nozzle ← downcomer; riser → jet pump driving nozzle | Downcomer nozzles |
| Break Modeling | Injection line stubs connect via side junctions to appropriate RPV cells | Core region / downcomer |
Fuel Channels¶
Not Yet Documented
Fuel channel and leakage SJC modeling guidance has not been completed. The BWR modeling guidance notes indicate this section will cover CHAN component inputs, axial nodalization, and radial channel grouping strategy based on ORNL recommendations, with applicability across different fuel vendors (GE, Westinghouse SVEA96, AREVA).
Heat Structures¶
RPV-associated heat structures (vessel wall, core shroud, core support plate, upper internals) follow the general heat structure guidance, adapted for BWR-specific geometries.
Cross-References¶
- Jet Pump — Connects to RPV downcomer/lower plenum
- Steam Separators — Connects to RPV upper plenum
- CRD Tubes — Spans RPV lower plenum through core bypass
- Recirculation Lines — Suction from RPV downcomer
- Containment — Receives break flow from RPV
- PWR Reactor Vessel — PWR 3D VESSEL guidance (more detailed, may provide useful reference for VESSEL component setup)
This page compiles BWR reactor vessel information inferred from other BWR component guidance sections. The vessel section of the BWR modeling guidance was in a preliminary draft stage and has not been fully developed. The RPV is modeled as a 3D VESSEL component with 2 radial rings, ≥13 axial levels, and 2 azimuthal sectors. Fuel channel and detailed vessel internals guidance is expected in future revisions.