fundamentals of relap.pdf

RELAP5 Fundamentals PEERAVUTH BOONSUWAN Bureau of Nuclear Safety and Regulation 20 September 2010

Introduction ƒ

The RELAP5 code is used to calculate the expected evolution of thermal-hydraulic properties during the postulated accident or transient, including all synergistic interaction between all system components. ƒ

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Assess and Demonstrate the Design & Safety of Nuclear Installations under Normal, Abnormal, Accident Conditions

What are the procedures of thermal-hydraulic System Analysis ? ƒ ƒ ƒ ƒ ƒ

Gather and Organize System Information Define Problem and Nodalize the System (Transient-Specific) Input Preparation Input Quality Assurance Running and Analyzing the Problem

STEPS

STEP 1: Gather Information `

RELAP5 Input Data is divided into 4 distinct areas: `

A: Hydrodynamics ` ` ` ` ` `

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All Flow Areas All Flow Lengths Vertical Orientation Geometric Details sufficient to Calculate Hydraulic Diameters Geometric Roughness at Fluid-wall Interfaces Sufficient Information to Calculate Flow Losses (e.g. Bend Geometries, Area Expansion, Geometry, Valve Geometries, Rated or Test Valve Flow Rates, Plant Startup Test Data) Initial Plant Conditions Pump Characteristics

B: Heat Structures C: Control Systems D: Neutronics

Sources of Information ` `

Safety Analysis Report Prints of Loop Piping in: ` ` ` ` ` ` ` `

Reactor Vessel Steam Generator Steam Lines Feed Train Pressurizer Reactor Coolant Pumps Accumulators Safety Injection Lines

Sources of Information (cont.) ` ` ` ` ` ` ` `

Piping and Instrumentation Diagrams Precautions, Limitations, and Specification Documents Operating Procedures Fuel and Reactor Kinetics Information Pump Characteristics Valve Information Plant Startup Test Data etc.

STEP 2: Defining the Problem and Nodalization the System ` ` ` `

Ask yourself this: “What do I want to study/simulate?” Then, Draw a boundary around the system that requires simulation. During the process of defining and nodalizing the problem, the user must carefully document each step. The user must properly model the boundary and initial conditions of the problem.

Nodalization At-a-Glance ` ` `

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Objective: To simplify bulky equipment into several connecting nodes for simulation. Must be careful on naming such nodes to ensure accuracy when preparing the input file. The number of nodes that represent each equipment is quite arbitary. The user must determine the optimal number to ensure validity and speediness of the calculations. To be discussed in details in the following sections/ handout.

Nodalization Example:

STEP 3: Input Preparation ` `

STEP 3 is the heart of performing thermalhydraulic simulation using RELAP5 Will be discussed in details in the section on “Hydrodynamic Model Input.”

STEP 4: Input Quality Assurance ` `

To ensure that what the user is putting into an input file is accurate and is easy to review. Input QA is done through documentation of the input preparation process: ` ` `

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Make a calculation note Be traceable Assumptions/Limitations/References

Independent Review To be discussed more in details

Example of a Calculation Worksheet

STEP 5: Running and Analyzing the Problem `

Problems of Running RELAP on the computer ` `

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Unexplanined Failures Unintended Sequence of Events

Analysis of the RELAP5 Results ` ` ` ` `

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Check the output for nonphysical results Check the calculation for results that may be unrealistic Boundary conditions should be checked to ensure that key events are occurring as prescribed Every aspect of the calculation should be thoroughly understood Early in the analysis phase, the user should use graphics so that all the necessary output is obtained

Think and Think Again!

INPUT PREPARATION

General User Guidelines (I) `

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RELAP5 is designed for use in analyzing system components interactions; it does not offer detailed simulations of fluid flow within components. As such, it contains limited ability to model multidimensional effects, either for fluid flow, heat transfer, or reactor kinetics. Hydrodynamic model consists of Volumes and Junctions that represent a flow path. All internal flow paths must be explicitly modeled such that only single liquid and vapor velocities are represented at a junction. Heat Flow paths are modeled in a 1-D sense, while 2-D heat conduction with automatic fine mesh rezoning is used for flooding.

General User Guidelines (II) `

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Point Reactor Kinetics model cannot consider certain nonlinear or multidimensional effects caused by spatial variations of the feedback parameters. It should be noted that the system codes contains numerous approximations limited by the computer resources, computing time, limited knowledge of physical phenomena of processes and components.

RELEP5 Input Data Cards (I) `

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Input Data: Assembly of Records or Cards having 80 charactors Input Requirement `

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Title Card: Title is identified by an equal sign (=) as the first non-blank character. Data Card: Card 1 ~ Card 5xxxxxxx Terminator Card: Input data are terminated by a slash(/) or a period (.) Details as described in the manual.

All About Syntax and Structure `

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Like a language, in order for RELAP5 to understand and perform simulations as we’d expect, we must speak its language. An input file is like a list of instructions or commands. In this section we’ll learn where to put information we have (from calculation we’ve done in STEP2) in the correct order that the program can understand.

RELAP5 Input Data Cards (II) `

Control Cards `

Card 1: Developmental Model Control ` `

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Ex. Option 70 Options 71

ASME’93 Dynamic Properties Deleted

Card 100: Problem Type and Option Card 101: Input Check and Run Option Card 102: I/O Units Selection • • • Card 200-299: Time Step Control Cards

(for furthur information consult RELAP5 Book 2)

RELAP5 Input Data Cards (III) `

Minor Edit Requests ` `

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Trip Input Data ` `

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Card Numbers: 400 – 799 JBINFO file includes the information for trip sequence

Hydrodynamic Input ` `

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Card Numbers: 300 ~ 399 Calculation Data of Minor Edit Variables are written in PLOFL file

Cards CCXXNN Compose the loop to simulate using hydrodynamic components

Heat Structure Input ` `

Card 1CCCGXNN Model the heat conductors or rods

RELAP5 Input Data Cards (IV) `

Heat Structure Thermal Property Input ` `

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General Table Input ` `

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Cards 202TTTNN Power or Heat Flux or HTC: Time, HTC: Temperature, …

Control System Input ` `

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Cards 201MMMNN Specify the thermal conductivity and heat capacity of heat structures

Cards 205CCCNN Define generic control components

Reactor Kinetics Input ` `

Cards 3XXXXXXX Specify the point reacto kinetics data

HYDRODYNAMIC MODEL INPUT

Hydrodynamic Model Input (I) ` ` `

Essential Unit: Volume and Junction Flow paths are connected from face to face of each volume Nodalization: Hydrodynamic System ➡ Volumes & Junctions

Example: Nodalization of a LWR Primary Loop

Hydrodynamic Model Input (II) `

Basic Elements of Hydrodynamic Input ` `

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Geometric Data: Flow Area, Length, Volume, Angle, Elevation Change, Wall Roughness, Hydraulic Diameter, Form Loss, Control Flag, etc. Initial Conditions: Pressure, Temperature, Quality, Flow, etc.

Volume Notation: cccnn00xx ` ` ` `

ccc : component number (volume is a member of a certain component) nn : node number 0000 : volume itself Volume face notation ` `

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00 : old format (if inlet face 00, outlet face 01 override the xx input) xx : face number (01: inlet, 02 : outlet, 03 : y-, 04 : y+, 05 : z-, 06 : z+

Junction Notation ` ` `

ccc : component number (junction is a member of a component) mm : node number 0000 : not used yet

Hydrodynamic Model Input (III)

Hydrodynamic Model Input (IV)

Hydrodynamic Model Input (V) `

RELAP5 Hydrodynamic Components ` ` ` ` ` ` ` ` ` `

Single Volume SNGLVOL Single Junction SNGLJUN Time-Dependent Volume TMDVOL Time-Dependent Junction TMDJUN Pipe PIPE N volumes & N-1 junctions Annulus ANNULUS N volumes & N-1 junctions, Annulus Geometry Branch BRANCH 1 volume & N junctions Separator SEPARATR 1 volume & 3 junctions, Separator functions Jet Mixer JETMIXER 1 volume & 3 junctions, Jet Mixer functions ECC Mixer ECCMIX 1 volume & 3 junctions, ECC mixer functions

(cont.) `

RELAP5 Hydrodynamic Components (cont.) ` `

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Turbine

TURBINE

1 volume & 1 or 2 junctions,

Turbine function Valve VALVE 1 junction, On/Off or Variable flow area Pump PUMP 1 volume & 2 junctions, CCP, Angular momemtum Multiple Junction MTPLJUN N junctions Accumulator ACCUM 1 volume & 1 junction, Accumulator function

General Guidelines for Hydrodynamics Modeling ` `

L/D > 1 except for special cases (PZR, …) Minimize Number of Volumes and Junctions ` `

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Computing Cost & Memory Limit: Current Limit ~ 1,000 Eliminate Minor Flow Paths that are insignificant to results

Length of Volume to have similar Courant Limit (L/v) Nodalization and Time Step Sensitivity for estimation of Calculation Uncertainty Avoid Sharp Density Gradients at Junctions Establish Flow and Pressure Boundaries at Locations beyond Interests Follow the Guidelines for Special Process Models (Abrupt Area, Choking, Branching, Reflood, CCFL, …) Follow the Guidelines for Special Components (Pump, Valves, Separator, Annulus, ECCMIXER, …)

Boundary and Initial Conditions (ICs) `

Boundary Conditions ` `

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Use Time-Dependent Volume and Time-Dependent Junctions to specify the boundary conditions Time-Dependent Volume: Specifies the flow conditions (pressure, temperature, void fraction, quality of noncondensables, etc.) Time-Dependent Junctions: Specifies the mass flow rate or velocities of each phase as a function of time or others. Don’t specify unphysical boundary conditions, such as specifying a negative mass flow rate from a volume.

Initial Conditions `

Specifies the initial conditions for all the volumes and junctions as realistic as possible.

A Sample Input for a Flow in a Vertical Pipe

Point Kinetics Input

Point Kinetics Input Data `

Model the Space-Independent Reactor Kinetics ` ` `

Reactivity Feedback: Mod. Tep, Mod. Density, Fuel Temp, Boron, … Reactivity Curve by Control Rod Motion Decay Power: ANS 73, ANS79-1~3, ANS94-4