The University of Southampton
University of Southampton Institutional Repository

Using thermal evolution profiles to infer tritium speciation in nuclear site metals: an aid to decommissioning

Using thermal evolution profiles to infer tritium speciation in nuclear site metals: an aid to decommissioning
Using thermal evolution profiles to infer tritium speciation in nuclear site metals: an aid to decommissioning
Understanding the association and retention of tritium in metals has significance in nuclear decommissioning programs and can lead to cost benefits through waste reduction and recycling of materials. To develop insights, a range of metals from two nuclear sites and one non-nuclear site were investigated which had different exposure histories. Tritium speciation in metals was inferred through incremental heating experiments over the range of 20–900 °C using a Raddec Pyrolyser instrument. Systematic differences in thermal desorption profiles were found for nonirradiated and irradiated metals. In nonirradiated metals (e.g., stainless steel and copper), it was found that significant tritium had become incorporated following prolonged exposure to tritiated water vapor (HTO) or tritium/hydrogen gas (HT) in nuclear facilities. This externally derived tritium enters metals by diffusion with a rate controlled by the metal composition and whether the surface of the metal had been sealed or coated prior to exposure. The tritium is normally trapped in hydrated oxides lying along grain boundaries. In irradiated metals, an additional type of tritium can form internally through neutron capture reactions. The amount formed depends on the concentration and distribution of trace lithium and boron in the metal as well as the integrated neutron flux. Liberating this kind of tritium typically requires temperatures above 800 °C. The pattern of tritium evolution derived from simple thermal desorption experiments allows reliable inferences to be drawn on the likely origin, location, and phases that trap tritium. Any weakly bound tritium liberated at temperatures of ?100 °C is indicative of mostly HTO interactions in the metal. Any strongly bound tritium liberated over the range of 600–900 °C is indicative of neutrogenic tritium formed via neutron capture by trace Li and B. Neutron capture by lithium is likely to be more significant than for boron based on lithium’s higher trace element abundance and neutron cross section. The time required for efficient thermal desorption of tritium ultimately depends on the metal composition, its tritium exposure history, integrated neutron flux, sample size, sample geometry, heating rate, and final desorption temperature.
0003-2700
9177-9185
Croudace, Ian W.
24deb068-d096-485e-8a23-a32b7a68afaf
Warwick, Phil E.
f2675d83-eee2-40c5-b53d-fbe437f401ef
Kim, Daeji
06902d3d-1389-4cd7-8b78-db8459d81378
Croudace, Ian W.
24deb068-d096-485e-8a23-a32b7a68afaf
Warwick, Phil E.
f2675d83-eee2-40c5-b53d-fbe437f401ef
Kim, Daeji
06902d3d-1389-4cd7-8b78-db8459d81378

Croudace, Ian W., Warwick, Phil E. and Kim, Daeji (2014) Using thermal evolution profiles to infer tritium speciation in nuclear site metals: an aid to decommissioning. Analytical Chemistry, 86 (18), 9177-9185. (doi:10.1021/ac502244a).

Record type: Article

Abstract

Understanding the association and retention of tritium in metals has significance in nuclear decommissioning programs and can lead to cost benefits through waste reduction and recycling of materials. To develop insights, a range of metals from two nuclear sites and one non-nuclear site were investigated which had different exposure histories. Tritium speciation in metals was inferred through incremental heating experiments over the range of 20–900 °C using a Raddec Pyrolyser instrument. Systematic differences in thermal desorption profiles were found for nonirradiated and irradiated metals. In nonirradiated metals (e.g., stainless steel and copper), it was found that significant tritium had become incorporated following prolonged exposure to tritiated water vapor (HTO) or tritium/hydrogen gas (HT) in nuclear facilities. This externally derived tritium enters metals by diffusion with a rate controlled by the metal composition and whether the surface of the metal had been sealed or coated prior to exposure. The tritium is normally trapped in hydrated oxides lying along grain boundaries. In irradiated metals, an additional type of tritium can form internally through neutron capture reactions. The amount formed depends on the concentration and distribution of trace lithium and boron in the metal as well as the integrated neutron flux. Liberating this kind of tritium typically requires temperatures above 800 °C. The pattern of tritium evolution derived from simple thermal desorption experiments allows reliable inferences to be drawn on the likely origin, location, and phases that trap tritium. Any weakly bound tritium liberated at temperatures of ?100 °C is indicative of mostly HTO interactions in the metal. Any strongly bound tritium liberated over the range of 600–900 °C is indicative of neutrogenic tritium formed via neutron capture by trace Li and B. Neutron capture by lithium is likely to be more significant than for boron based on lithium’s higher trace element abundance and neutron cross section. The time required for efficient thermal desorption of tritium ultimately depends on the metal composition, its tritium exposure history, integrated neutron flux, sample size, sample geometry, heating rate, and final desorption temperature.

This record has no associated files available for download.

More information

Accepted/In Press date: 26 August 2014
e-pub ahead of print date: 26 August 2014
Published date: 16 September 2014
Organisations: Geochemistry

Identifiers

Local EPrints ID: 369839
URI: http://eprints.soton.ac.uk/id/eprint/369839
ISSN: 0003-2700
PURE UUID: fd9927b2-ca26-4819-a917-d9825224888c
ORCID for Phil E. Warwick: ORCID iD orcid.org/0000-0001-8774-5125

Catalogue record

Date deposited: 07 Oct 2014 13:29
Last modified: 13 Oct 2022 01:34

Export record

Altmetrics

Contributors

Author: Ian W. Croudace
Author: Phil E. Warwick ORCID iD
Author: Daeji Kim

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×