Tritium Speciation in Nuclear Reactor Bioshield Concrete and its Impact on Accurate Analysis

Abstract

Tritium ((3)H) is produced in nuclear reactors via several neutron-induced reactions [(2)H(n, gamma)(3)H, (6)Li(n, alpha)(3)H, (10)B(n, 2alpha)(3)H, (14)N(n, (3)H)(12)C, and ternary fission (fission yield <0.01%)]. Typically, (3)H is present as tritiated water (HTO) and can become adsorbed into structural concrete from the surface inward where it will be held in a weakly bound form. However, a systematic analysis of a sequence of subsamples taken from a reactor bioshield using combustion and liquid scintillation analysis has identified two forms of (3)H, one weakly bound and one strongly bound. The strongly bound tritium, which originates from neutron capture on trace lithium ((6)Li) within mineral phases, requires temperatures in excess of 350 degrees C to achieve quantitative recovery. The weakly bound form of tritium can be liberated at significantly lower temperatures (100 degrees C) as HTO and is associated with dehydration of hydrous mineral components. Without an appreciation that two forms of tritium can exist in reactor bioshields, the (3)H content of samples may be severely underestimated using conventional analytical approaches. These findings exemplify the need to develop robust radioactive waste characterization procedures in support of nuclear decommissioning programs.

Liquid scintillation counting for determination of radionuclides in environmental and nuclear application

“…A comparison of the Hidex 300SL with Quantulus 1414 and TriCarb 2800 in different labs by measurement of 89 Sr standard solution has also demonstrated a good performance of this method [1]. Hidex TDCR LSA has also been successfully applied for the measurement of 3 H, 63 Ni, 68 Ga, 99 Tc and 228 Ra and 210 Pb in environmental and waste samples [3,17,[39][40][41], it was also used for the determination 68 Ga 51 Cr, 90 Sr and 32 P in various biological samples [20,[42][43].…”

“…The determination of radionuclides using plastic scintillation resin and conventional LSC instrument has being proposed and shown a promising application, especially for the rapid analysis, which can avoid the utilization of the organic scintillator, therefore reduce the organic radioactive waste [5][6][7][8]. In the past years, an increased Journal of Radioanalytical and Nuclear Chemistry 4 application of LSC occurred in the measurement of radionuclides for decommissioning of nuclear facilities, such as 36 Cl, 41 Ca, 55 Fe, 63 Ni, 93 Zr, 99 Tc and 129 I [9][10][11][12][13][14][15][16]. The LSC has also shown a competitive application in the rapid analysis of radionuclides for emergency preparedness and homeland security purposes due to its relative short measurement time and simple target preparation [17][18][19][20].…”

Editors' Choice—Review—Electro-Kinetic Decontamination of Radioactive Concrete Waste from Nuclear Power Plants

“…The U.S. National Regulatory Commission (NRC) collected and analyzed concrete samples from bio-shield concrete walls during actual decommissioning projects. 53,54 The target radionuclides selected for this analysis were 152, 154, 155 Eu, 60 Co, 54 Mn, 63 Ni, 59 Fe, 160 Tb, 182 Ta, 181 Hf, 51 Cr, 124 Sb, 134 Cs, 85 Sr, 46 Sc, and 65 Zn. Fig.…”

A New Reference Material for Tritium Organic Molecules in Sediment: Results of an International Intercomparison Exercise

“…GAU‐Radioanalytical had previously investigated the significance of 3 H speciation in determining its stability in decommissioning (Kim et al . ) and environmental (Croudace et al . ) matrices and had demonstrated that the radiopharmaceutical‐derived TOM record in Severn Estuary sediments was preserved over a 30‐year timescale (Croudace et al .…”

“…It was agreed to address the current shortage through a series of intercomparison exercises organised by the working group, with exercises focussing on OBT reference materials for potato, sediment, wheat and grass . GAU-Radioanalytical had previously investigated the significance of 3 H speciation in determining its stability in decommissioning (Kim et al 2008) and environmental matrices and had demonstrated that the radiopharmaceutical-derived TOM record in Severn Estuary sediments was preserved over a 30year timescale . Based on this identified stability, it was proposed to use radiopharmaceutical discharge-derived materials to prepare a stable TOM in sediment NMRM.…”