**RSICC CODE PACKAGE PSR-395**

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**1. NAME AND TITLE**

LAPUR 6: BWR Core Stability Measurements.

**2. CONTRIBUTORS**

Oak Ridge National Laboratory, Oak Ridge, Tennessee.

**3. CODING LANGUAGE AND
COMPUTER**

Microsoft Fortran PowerStation 4.0; Personal Computer (P00395PC58602).

**4. NATURE OF PROBLEM
SOLVED**

LAPUR6 is a mathematical description of the core of a boiling water reactor (BWR). The program uses a point kinetics description of the neutron dynamics together with a distributed-parameter model of the core thermal hydrodynamics to produce a space-dependent representation of the dynamics of a BWR in the frequency domain for small perturbations about a steady-state condition. LAPUR6 consists of two autonomous modules, LAPUR6X, the steady-state module, and LAPUR6W the dynamics module, which are linked by use of an intermediate storage device. LAPUR6X solves the coolant and the fuel steady-state governing equations while LAPUR6W solves the dynamic equations for the coolant, fuel, and neutron field in the frequency domain. Considerable detail exists in the modeling of the thermohydrodynamics and the reactivity feedbacks.

The original version of LAPUR was limited to seven thermal-hydraulic regions (i.e., channels); LAPUR 6 was verified with up to 200 channels, each of which can have its own axial and radial power shape. The maximum number of frequencies was parameterized. The default value is 100. All code dimensions are now parameterized and can be increased if necessary. Default values and more details are noted in the user’s manual. The main upgrade in LAPUR 6 is the ability to model part-length fuel rods and fuel spacers explicitly. General implementation descriptions are followed by a detailed description of input and output parameters of LAPURX and LAPURW.

**5. METHOD OF SOLUTION**

LAPUR6X performs the steady-state and initialization calculations and generates maps of the thermohydraulic core parameters. The maps are stored in two data files for subsequent utilization by LAPUR6W. LAPUR6W solves the dynamic equations in the frequency domain for small perturbations about the steady-state conditions and generates a set of transfer functions from which stability indices are estimated. LAPUR6X generates the steady-state core parameters which include the channel flow rate, pressure drops, and exit quality (or power) for each channel, the nodal coolant density, void fraction, enthalpy, quality, velocities, and friction components at each node along each channel, and the set of coefficients for the dynamics calculation. LAPUR6W determines the fuel transfer function, coolant dynamic parameters, coolant transfer functions, reactivity feedback, and neutronic and system transfer functions.

**6. RESTRICTIONS OR
LIMITATIONS**

All code dimensions are now parameterized and can be increased if necessary.

**7. TYPICAL RUNNING TIME**

The two sample problems ran in a few seconds on a Pentium 4 2.8 GHz.

**8. COMPUTER HARDWARE
REQUIREMENTS**

LAPUR6.2 has been implemented on Pentium computers.

**9. COMPUTER SOFTWARE
REQUIREMENTS**

The Microsoft Fortran PowerStation 4.0 compiler was used to build the included executables. These were tested on Pentium computers under Windows2000 Service Pack 4 and WindowsXP Service Pack 3. The Fortran source files contain some Fortran IV and other legacy statements and may require modifications for other compilers.

**10. REFERENCES**

** a included
in the package:**

A. Escrivá, J. L. Muńoz Cobo, J. M. San Roman, M Albendea Darriba, and J. March-Leuba, “LAPUR6 Verification and User’s Manual,” NUREG/CR-6958 ORNL/TM-2007/233 (October 2008).

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** b. background
references:**

P. J. Otaduy and J. March-Leuba, “LAPUR User’s Guide,” NUREG/CR-5421, ORNL/TM-11285 (January 1990).

J. March-Leuba and P. J. Otaduy, “A Comparison of BWR Stability Measurements with Calculations Using the Code LAPUR-IV,” NUREG/CR-2998, ORNL/TM-8546 (January 1983).

J. March-Leuba, “Lapur Benchmark Against In-Phase and Out-of-Phase Stability Tests,” NUREG/CR-5605, ORNL/TM-11621 (October 1990).

P. J. Otaduy-Benoga, “Modeling of the Dynamic Behavior of Large Boiling Water Reactor Cores,” PH.D. Dissertation, University of Florida (1979).

**11. CONTENTS OF CODE
PACKAGE**

Included in the package are the referenced document in 10.a, source code, make files, and Windows executables, along with test case input/output in a WinZIP file on a CD.

**12. DATE OF ABSTRACT**

April 1999, revised November 2004 and June 2009.

**KEYWORDS:** FLUID
DYNAMICS; HEAT TRANSFER