The Critical Role of Nuclear Data Libraries in Reactor Simulation with the ORIGEN 2 Code

The ORIGEN 2 code is established as a standard tool for calculating isotope generation and depletion in nuclear reactors. The success of this code is entirely dependent on the accuracy and completeness of its nuclear data libraries. This paper provides a comprehensive examination of ORIGEN 2 libraries, their paramount importance in simulation, the appropriate context for their use, and the correct methodology for their implementation.

1. Introduction to the Importance of Nuclear Data Libraries

1.1 The Critical Role of Nuclear Data in Simulation

In nuclear reactor calculations, the accuracy of the results is directly dependent on the quality of the input data. The ORIGEN 2 libraries contain a comprehensive set of physical parameters, including:

• Neutron cross-sections at different energies

• Half-lives of radioactive isotopes

• Fission products and nuclear interactions

• Fission yields for various isotopes

• Decay chain data

Without these datasets, simulating the behavior of nuclear fuel over time would be impossible.

1.2 The Challenges of Compiling Nuclear Data

Compiling accurate nuclear data is one of the most complex steps in reactor physics because:

• Neutron cross-sections depend on reactor energy spectrum and temperature

• Decay data for unstable isotopes require precise experimental measurements

• Fission products are highly diverse, and their interactions are complex

• Data must be tailored for different reactor operating conditions

2. Categorization of ORIGEN 2 Libraries and Their Specific Importance

2.1 Fundamental Libraries: The Absolute Necessity for Simulation

Decay Library (DECAY.LIB)
This library is the beating heart of any ORIGEN 2 simulation. It includes:

• Half-lives of 1,671 radioactive isotopes

• Energy and intensity of particles emitted in decays

• Various decay probabilities for each isotope

• Daughter products resulting from decay
  Without this library, calculations of decay kinetics and the buildup of fission products are impossible.

Thermal Cross-Section Library (THERMAL.LIB)
Contains thermal neutron cross-sections for:

• Fuel isotopes (Uranium, Plutonium)

• Poison fission products

• Reactor structural materials

• Moderator materials

2.2 Reactor-Specific Libraries: Matching Real-World Conditions

PWR (Pressurized Water Reactor) Libraries

• PWRU.LIB: Base data for uranium fuel

• PWRUE.LIB: For fuel with different enrichment levels

• PWRPUPU.LIB: For pure plutonium fuel

• PWRPUU.LIB: For mixed Uranium-Plutonium (MOX) fuel
  Each of these libraries is optimized for specific PWR operational conditions.

BWR (Boiling Water Reactor) Libraries

• BWRU.LIB: Base BWR data

• BWRUS.LIB: For spent fuel

• BWRPUPU.LIB: For plutonium fuel in BWRs
  The main differences lie in neutron density and energy spectrum, which differ between BWRs and PWRs.

2.3 Advanced Libraries: For Specialized Applications

Molybdenum Libraries (AMO/EMOP Series)
These libraries were developed for advanced fuel systems containing molybdenum:

• AMO0TTTA.LIB, AMO0TTTC.LIB, AMO0TTTR.LIB: For base enrichment levels

• AMOPUUUA.LIB, AMOPUUUC.LIB, AMOPUUUR.LIB: For Plutonium-Uranium-Molybdenum systems

The suffixes indicate the data type:

• A: Absorption cross-sections

• C: Capture cross-sections

• R: Reaction Rates

Bremsstrahlung Cross-Section Libraries

• GXUO2BRM.LIB: For Uranium Dioxide

• GXH2OBRM.LIB: For water as a moderator

• GXNOBREM.LIB: For Nitrogen Oxide
  These libraries are essential for radiation dose and shielding calculations.

3. When and Under What Conditions to Use Different Libraries

3.1 Library Selection Based on Reactor Type

• Research Reactors: CRBRA.LIB, CRBRC.LIB

• PWR Power Reactors: PWR family

• BWR Power Reactors: BWR family

• CANDU Reactors: CANDUNAU.LIB, CANDUSEU.LIB

3.2 Selection Based on Fuel Composition

• Enriched Uranium Fuel: PWRU.LIB, BWRU.LIB

• MOX Fuel: PWRPUU.LIB, BWRPUU.LIB

• Plutonium Fuel: PWRPUPU.LIB

• Thorium Fuel: PWRPUTH.LIB, PWRDU3TH.LIB

3.3 Selection Based on Burnup Stage

• Beginning of Life (BOL): Base libraries (PWRU.LIB, BWRU.LIB)

• Advanced Burnup: High-burnup libraries (PWRUS.LIB, BWRUS.LIB)

• Post-Irradiation Calculations: Combination with the decay library

4. Correct Methodology for Importing Libraries into ORIGEN 2

4.1 Standard Library Call Structure

In an ORIGEN 2 batch file, libraries are typically called as follows:

copy ..\libs\decay.lib+..\libs\pwru.lib tape9.inp
copy ..\libs\gxuo2brm.lib tape10.inp

4.2 Correct Order for Merging Libraries

The order of library merging is crucial:

1. The Decay Library must always be the foundation

2. Base Cross-Section Libraries based on reactor type

3. Specialized Libraries based on fuel composition

4. Auxiliary Libraries for specific calculations

4.3 Managing Common Errors

• Library Not Found Error: Verify file paths

• Data Incompatibility Error: Ensure library compatibility

• Data Format Error: Use version-appropriate libraries

5. Comprehensive List of ORIGEN 2 Libraries

5.1 Fundamental & Essential Libraries

• DECAY.LIB (Decay data)

• THERMAL.LIB (Thermal cross-sections)

• FFTFC.LIB (Fast neutron cross-sections)

5.2 Pressurized Water Reactor (PWR) Libraries

• PWRU.LIB (Base uranium data)

• PWRU50.LIB (Uranium with specific burnup)

• PWRUE.LIB (Enriched uranium)

• PWRUS.LIB (Spent fuel)

• PWRPUPU.LIB (Plutonium)

• PWRPUTH.LIB (Plutonium-Thorium)

• PWRPUU.LIB (Plutonium-Uranium)

• PWRD5D33.LIB, PWRD5D35.LIB (Advanced burnup data)

• PWRDU3TH.LIB (Uranium-Thorium)

5.3 Boiling Water Reactor (BWR) Libraries

• BWRU.LIB (Base data)

• BWRUE.LIB (Enriched uranium)

• BWRUS.LIB, BWRUS0.LIB (Spent fuel)

• BWRPUPU.LIB (Plutonium)

• BWRPUU.LIB (Plutonium-Uranium)

5.4 CANDU Reactor Libraries

• CANDUNAU.LIB (Natural uranium)

• CANDUSEU.LIB (Slightly enriched uranium)

5.5 Research Reactor Libraries

• CRBRA.LIB, CRBRC.LIB, CRBRI.LIB, CRBRR.LIB

5.6 Molybdenum Libraries (AMO Series)

• AMO0TTTA.LIB, AMO0TTTC.LIB, AMO0TTTR.LIB

• AMO1TTTA.LIB, AMO1TTTC.LIB, AMO1TTTR.LIB

• AMO2TTTA.LIB, AMO2TTTC.LIB, AMO2TTTR.LIB

• AMOPTTTA.LIB, AMOPTTTC.LIB, AMOPTTTR.LIB

• AMOPUUTA.LIB, AMOPUUTC.LIB, AMOPUUTR.LIB

• AMOPUUUA.LIB, AMOPUUUC.LIB, AMOPUUUR.LIB

• AMORUUUA.LIB, AMORUUUC.LIB, AMORUUUR.LIB

• EMOPUUUA.LIB, EMOPUUUC.LIB, EMOPUUUR.LIB

5.7 Bremsstrahlung Cross-Section Libraries

• GXH2OBRM.LIB (Water)

• GXNOBREM.LIB (Nitrogen Oxide)

• GXUO2BRM.LIB (Uranium Dioxide)

6. Conclusion and Practical Recommendations

The ORIGEN 2 libraries are powerful tools for the accurate simulation of nuclear fuel behavior. Successful simulation requires:

1. Selecting the appropriate library for the reactor and fuel type.

2. Correctly ordering the sequence of library calls.

3. Validating results with experimental data.

4. Continuously updating libraries with new data.

It is recommended that ORIGEN 2 users always work with the most recent library versions and consistently compare their results with empirical measurements.

References:

• ORIGEN 2 User Manual, Oak Ridge National Laboratory

• SCALE Code System Documentation

• ENDF/B Nuclear Data Libraries

• IAEA Nuclear Data Services