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Request ID45 Status of the request High Priority request
TargetReaction and processIncident EnergySecondary energy or angleTarget uncertaintyCovariance
 19-K-39 (n,p),(n,np) SIG  10 MeV-20 MeV  10 Y
FieldSubfieldDate Request createdDate Request acceptedOngoing action
 Fusion  17-MAY-17 11-JUL-17 

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Requester: Dr Stanislav SIMAKOV at KARLSRUHE, GER

Project (context): IFMIF and DONES material test facilities, and fusion power plants

The 39K(n,p) reaction produces 39Ar with decay half-life of 269 years and makes the dominant contribution to the long-lived radioactive inventories in NaK. The latter is considered as a coolant of specimens in the accelerator driven irradiation facilities that are designed now for the fusion material testing (IFMIF [1], DONES [2] ...). Together with the competing reaction 39K(n,np)38Ar they also determine the total amount of Argon gas which impact on the thermal and mechanical properties of sealed specimens containers [3]. The current poor knowledge of these two reactions questions whether NaK could be used in the IFMIF and DONES design. Additionally, since potassium is present in cement and concrete, the 39K(n,p)39Ar reaction impacts on the long-term radioprotection and shielding issues in IFMIF/DONES testing vaults and future fusion power plants.

The continuous Argon gas leakage through cracks in the welding of sealed containers or their accidental rupture is a complex process. Because of this complexity, the sensitivity analyses quantifying the required accuracy of the cross sections have never been done. However, considering the potentially high impact and the poor knowledge of these cross sections, a request for 10% accuracy is a reasonable requirement that will be practically achievable by utilizing the current techniques. This requirement is supported by the fusion and general nuclear data users.

Justification document:

At 14 MeV neutron energy 3 measurements by proton spectroscopy and activation [4-6] reported 3 times larger value for 39K(n,p)39Ar reaction cross section than measurement by AMS [7]. For competing reaction 39K(n,np)38Ar the situation is vice versa. See Ref. [3] for more information.

The main evaluated libraries are similarly discrepant depending on which experiment they follow.

The new measurement is needed first at 14 MeV to resolve this contradiction.


  • [1] F. Arbeiter et al., Nuclear Materials and Energy 9 (2016)59.
  • [2] A. Ibarra et al., Fusion Science and Technology 66 (2014) 252.
  • [3] S.P. Simakov, Y. Qiu, U. Fischer, EFFDOC-1318, JEFF Meeting, OECD, Paris, April 24-27, 2017.
  • [4] M. Bormann et al., Zeitschrift fuer Naturforschung A 15 (1960) 200.
  • [5] D.V. Aleksandrov, L.I. Klochkova, B.S. Kovrigin, Soviet Atomic Energy 39 (1975) 736 (translated from Atomnaya Energiya 39 (1975) 137).
  • [6] W. Schantl, PhD thesis, Institut für Radiumforschung und Kernphysik, University of Vienna, 1970.
  • [7] K.A. Foland, R.J. Borg, M.G. Mustafa, Nuclear Science and Engineering 95 (1987) 128.

Comment from requester:

Comments from evaluator/experimentalist:

Comments for achieved accuracy:

Review comment:

Additional file attached: effdoc-1318.pdf