| ID | 115 |
|---|---|
| Type | H - High priority request |
| Target | 94-Pu-239 |
| Reaction | (n,tot) |
| Quantity | SIG - Cross section |
| Incident energy | Thermal - 5 eV |
| Accuracy | 1 % |
| Field(s) | Fission |
| Subfield | Thermal reactors |
| Accepted date | 08-Apr-2019 |
| Status | Work in progress |
| Latest review date | 28-Apr-2022 |
Requester
Dr Gilles NOGUERE at CAD-DER, FR
Impact
The use of new high-accuracy transmission data in the evaluation procedure will affect the partial cross sections and their uncertainties, whose impact on neutronic calculations may be significant. For the first resonance the uncertainty on capture is 2.5% in JEFF-3.3 and 4% in ENDF/B-VIII.0, whereas the sensitivity of keff to capture is close to 200 pcm/% for MOX fuel. Hence, any modifications of the resonance parameters and their uncertainties will have a sizeable impact on reactor applications.
Accuracy
Accuracy and precision better than 1% are required for the first resonance.
Justification document
New experimental setups are developed to measure the capture cross sections of actinides in the resolved resonance range. However, total cross sections are also important quantities for evaluation purposes.
The transmission data of the first resonance have all been measured in the 1950's (see attached figure).
Uncertainty information on these old measurements are scarce or lacking and does not help much to constrain the resonance parameters in the evaluation process, which is a pity given the high accuracy that can be reached on a transmission measurement (compared to capture). The attached figure illustrates how ENDF/B-VIII.0 and JEFF-3.3 differs, partly because of evaluators' choices, but also because of poor uncertainty information.
New high-accuracy transmission measurements of the first resonance will help improve the resonance parameters and reduce the uncertainty on the capture cross section.
Entry status
Work in progress (as of SG-C review of June 2019)
Main recent references
Please report any missing information to hprlinfo@oecd-nea.org
