237-Np. Research into problems relating to purification, characterisation and standardisation.

Project Description

The purpose of the project is to conduct research into the actinide 237-Np. Because of its halflife (7.82 E+8 days), this radionuclide will exhibit an increasingly important profile in the inventory of radioactive materials in the environment, resulting from their production and subsequent release from the nuclear power cycle. It is important that the characteristics of this radionuclide are well-defined and that agreement on primary standards of 237-Np is established internationally. Primary standards may be established using the conventional techniques but their subsequent dissemination to the user community and the ability of that community to use secondary standards and analytical techniques relies on a sufficiently accurate set of decay scheme data. In particular this data relates to alpha and gamma emission probabilities and to the half-life value. The ability to determine such data and standards also requires a high level of radioactive purity. The project is designed to provide that data and to demonstrate equivalence between national standards.

It is proposed that suitable raw material be identified and purified (where necessary) by mid-1997 allowing sources to be prepared in June/July. This will allow about 6 months for equilibrium to be reestablished with the 233-Pa daughter prior to distribution of samples in Jan 1998. The deadline for return of experimental results is planned for June 1998.

Final Report 2002-03-13

The project has been completed and results are published in the KCDB.

It was shown that the pure 237Np could be obtained using available radiochemical separation procedures. A successful standardisation was conducted both by primary and secondary standardisation techniques including the defined solid angle method, coincidence counting, 4πα and 2πα counting, liquid scintillation, and calibrated gamma spectrometry.
Samples were transmitted to the BIPM SIR system that allowed equivalence to be established between the participating laboratories. Both alpha and gamma emission probabilities were measured resulting in more accurate data for a number of transitions. Some transitions were identified as requiring more work. Results of the total project were published both as an NPL report and as the result of a presentation at the ICRM Scientific Meeting in 2001.

References:

Results from the 237Np exercise, EUROMET action 416
D.Smith, M.J.Woods, D.H.Woods. NPL Report CIRM 43, April 2001

Standardization and decay data of 237Np.
M. J. Woods, D. H. Woods, S. A. Woods, L. J. Husband, S. M. Jerome, C. Michotte, G. Ratel, M. Crespo, E. Garcia-Torano, L. Rodriguez et al. Appl. Rad. Isot.,
Vol 56, pp 415-420 (2002)