Disentangling the ¹⁶O cross section using light water and heavy water benchmark assemblies

Area of Science:

• Nuclear Physics
• Neutron Transport

Background:

• Neutron leakage spectra are crucial for nuclear reactor design and safety.
• Accurate nuclear data libraries are essential for simulating neutron transport.

Purpose of the Study:

• To measure fast neutron leakage spectra from light and heavy water spheres.
• To compare experimental data with MCNP transport code calculations using different nuclear data libraries.
• To evaluate the performance of ENDF/B-VII.0, ENDF/B-VIII.b4, and JENDL-4 libraries.

Main Methods:

• Neutron leakage spectra were measured using a stilbene scintillation detector.
• Measurements were conducted on 30cm diameter light and heavy water spheres with a central Californium-252 (²⁵²Cf) neutron source.
• MCNP transport code was used for theoretical calculations.

Main Results:

• Experimental results showed similar trends for both light and heavy water spheres.
• The ENDF/B-VIII.b4 library demonstrated the best agreement with experimental measurements.
• All evaluated libraries underestimated the experimental data in the 3-4 MeV region.
• The JENDL-4 library overestimated experimental data between 4-6.5 MeV.

Conclusions:

• The ENDF/B-VIII.b4 library provides a more accurate representation of neutron transport in water spheres compared to ENDF/B-VII.0 and JENDL-4.
• Discrepancies in specific energy regions highlight areas for improvement in nuclear data evaluations, particularly for oxygen-16 (¹⁶O).
• Cross-section sensitivity analysis identified key reactions influencing neutron leakage spectra.