The in-situ production of radioisotopes in rock matrices with particular reference to the stripa granite

Andrews, J.N.; Davis, S.N.; Fabryka-Martin, J.; Fontes, J.-Ch.; Lehmann, B.E.; Loosli, H.H.; Michelot, J.-L.; Moser, H.; Smith, B.; Wolf, M. (1986). The in-situ production of radioisotopes in rock matrices with particular reference to the stripa granite. Geochimica et cosmochimica acta, 53(8), pp. 1803-1815. Elsevier Science 10.1016/0016-7037(89)90301-3

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The in situ production of 3H, 14C, 36Cl, 129I, 37Ar, 39Ar, 81Kr and 85Kr by neutron-induced reactions and spontaneous nuclear decay processes has been estimated within the Stripa granite, its associated fracture minerals and surrounding leptite. Experimental measurements of the neutron flux within the Stripa granite are within 15% of theoretical values and have been used to calculate neutron-induced production rates. Activities of radionuclides that may enter groundwaters from the rock matrix are discussed in relation to their initial distribution in the host rock and their subsequent release into solution. The measured radioactivities in groundwaters from the high radioélément-content granites at Stripa are compared with estimates of their in situ production within the granite and of their solution by fracture-borne fluids. The activities of 3H and 14C which enter fracture fluids from the rock matrix are close to present detection limits. For 3H, the most significant production is within the rock matrix whilst for 14C it is within the circulating fracture fluids. Chlorine-36 production by neutron-capture within the granite is much more significant than inputs from cosmogenic and nuclear fallout sources. The 36ClCl ratio may be used to evaluate Cl− sources in saline groundwaters. In situ production of 129I by spontaneous fission of 238U is an important source of 129I in the high radioactivity Stripa granite. Argon-37, 39Ar and 85Kr are produced by in situ reactions within the rock matrix, fracture mineralisation and at the sites of U-mineralisation, respectively. The use of some cosmogenic radionuclides for the estimation of groundwater residence times may be limited because of in situ production.

Item Type:	Journal Article (Original Article)
Division/Institute:	08 Faculty of Science > Physics Institute > Climate and Environmental Physics
UniBE Contributor:	Lehmann, Bernhard, Loosli, Heinz Hugo
Subjects:	500 Science > 530 Physics
ISSN:	0016-7037
Publisher:	Elsevier Science
Language:	English
Submitter:	BORIS Import 2
Date Deposited:	15 Sep 2021 16:53
Last Modified:	05 Dec 2022 15:52
Publisher DOI:	10.1016/0016-7037(89)90301-3
URI:	https://boris.unibe.ch/id/eprint/158820