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Photonuclear cross-section measurements for the production of medical radioisotope Actinium-225

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225Ac is a high energy alpha-emitting radioisotope with potential therapeutic applications for Targeted Alpha Therapy (TAT). TAT is a cancer treatment method based on the high Linear Energy Transfer (LET) of alpha particles resulting in a short range and dense ionization tracks in tissue.

The idea of using 225Ac and its daughter 213Bi for targeted alpha therapy (TAT) is known since 1993 [1]. In 2013, the compound 225Ac-PSMA617 was first synthesized and investigated at JRC Karlsruhe. The great efficacy of this novel compound was reported by Kratochwil et al. in 2016 [2]. Great benefit observed clinically in many patients stimulated worldwide interest in applying 225Ac in TAT. Consequently, a number of novel 225Ac-labeled compounds are currently under development [3], and several institutions (as non-European, as European) are setting up the facilities or production lines, which can help to satisfy the growing demand in 225Ac for further clinical studies.

Nowadays 225Ac is obtained from 229Th generators coming from 233U. Thus the supply of 225Ac is limited by current 229Th stocks available worldwide. As of 2021, the available quantity of 229Th is not sufficient to satisfy the needs for the large-scale clinical trials and worldwide cancer treatment. Accelerator-based production of 225Ac from 226Ra is a possible solution to overcome this limitation.

One of potential production routes for 225Ac is photonuclear reaction on 226Ra, i.e. 226Ra(γ,n) followed by beta-decay of 225Ra. Nuclear data on the 226Ra(γ,n)225Ra reaction, essential for determining ideal irradiation conditions and for evaluating the feasibility of this production route, is currently based on theoretical estimations. Up to date, only two measurements on the integral 225Ra/225Ac production yield have been reported in scientific literature [4, 5]. To improve this situation, experimental measurements at the recently installed new beamline of the GELINA electron accelerator will be carried out. The beamline allows direct irradiations with quasi-mono-energetic electron beams in the electron energy range between 20 MeV and 130 MeV. These electron beams produce the needed γ radiation field by irradiating a high-Z material converter.

The main scope of the project is to determine yields of the photonuclear reaction 226Ra(γ,n)225Ra and improve our knowledge of the cross section using the new GELINA beam line for irradiation with high energy photons. The cross-section is to be evaluated in the range 5-25 MeV.

[1] Geerlings M.W., et al. Nucl Med Commun. 14:121-125, 1993

[2] Kratochwil, C., et al. Journal of Nuclear Medicine. 2016;57(12):1941-1944.

[3] Morgenstern, et al. Seminars in Nuclear Medicine. 2020;50(2):119-123.

[4] Melville, G., et al. Applied Radiation and Isotopes. 2007;65(9):1014-1022

[5] Maslov, O.D., et al. Radiochemistry. 2006;48(2):195-197.

The minimum diploma level of the candidate needs to be

  • Master of sciences
  • Master of sciences in engineering
  • MD

The candidate needs to have a background in

  • Chemistry
  • Physics
  • nuclear physics/applied physics/medical physics/nuclear engineering/nuclear chemistry/radiochemistry. Experience in Monte Carlo simulations software (MCNP, PHITS, FLUKA); 3D CAD modelling; alpha, gamma spectroscopy; basic (radio)chemistry is a plus

Estimated duration

4 years

Expert group


SCK CEN Mentor

Skliarova Hanna
hskliaro [at]
+32 (0)14 33 82 33

SCK CEN Co-mentor

Heinitz Stephan
sheinitz [at]
+32 (0)14 33 82 16


Maëlle Kerveno
maelle.kerveno [at]


Jan Wagemans
jan.wagemans [at]