A review of the potential for radium from luminising activities to migrate in the environment

Radon Off-Gassing From Military Artifacts

Military historical artifacts found in museum displays and storage locations were analyzed for their Ra and Rn progeny activities to determine the fraction of Rn lost to the environment. Gamma-ray spectroscopy using high-purity germanium detectors was used to determine Ra activity and infer Rn activity based on Pb and Bi. Analyses were conducted without affecting the structural integrity of the artifacts. Ra was measured directly after correction for solid angle and finite sample-detector distance. Although Rn can be similarly analyzed, the collection in charcoal of Rn off-gassed from the artifact after the establishment of secular equilibrium was preferable. Rn off-gassing rates vary greatly between the six devices studied, with a maximum off-gassing rate of 1,850 ± 50 Bq h. Large variations in off-gassing rate were also observed between an additional 30 nominally identical dials, with a mean and standard deviation of 7.7 ± 7.1 Bq h. The work is not predictive of airborne Rn activity within museums, where building size and ventilation are significant and unique to each location. However, the significant off-gassing rates and their large variation suggest that Rn activities may be elevated in enclosed locations, such as aircraft cockpits and storage facilities.

Remediating radium contaminated legacy sites: Advances made through machine learning in routine monitoring of "hot" particles

The extensive use of radium during the 20th century for industrial, military and pharmaceutical purposes has led to a large number of contaminated legacy sites across Europe and North America. Sites that pose a high risk to the general public can present expensive and long-term remediation projects. Often the most pragmatic remediation approach is through routine monitoring operating gamma-ray detectors to identify, in real-time, the signal from the most hazardous heterogeneous contamination (hot particles); thus facilitating their removal and safe disposal. However, current detection systems do not fully utilise all spectral information resulting in low detection rates and ultimately an increased risk to the human health. The aim of this study was to establish an optimised detector-algorithm combination. To achieve this, field data was collected using two handheld detectors (sodium iodide and lanthanum bromide) and a number of Monte Carlo simulated hot particles were randomly injected into the field data. This allowed for the detection rate of conventional deterministic (gross counts) and machine learning (neural networks and support vector machines) algorithms to be assessed. The results demonstrated that a Neural Network operated on a sodium iodide detector provided the best detection capability. Compared to deterministic approaches, this optimised detection system could detect a hot particle on average 10cm deeper into the soil column or with half of the activity at the same depth. It was also found that noise presented by internal contamination restricted lanthanum bromide for this application.

Radium dial watches, a potentially hazardous legacy?

This study re-examines the risk to health from radium ((226)Ra) dial watches. Ambient dose equivalent rates have been measured for fifteen pocket watches giving results of up to 30 μSv h(-1) at a distance of 2 cm taken with a series 1000 mini-rad from the front face (arithmetic mean ambient dose equivalent for pocket watches being 13.2 μSv h(-1)). A pocket compass gave rise to a similar ambient dose equivalent rate, of 20 μSv h(-1), to the pocket watches, with its cover open. Eighteen wristwatches have also been assessed, but their dose rates are generally much lower (the arithmetic mean being 3.0 μSv h(-1)), although the highest ambient dose equivalent rate noted was 20 μSv h(-1). A phantom experiment using a TLD suggested an effective dose equivalent of 2.2 mSv/y from a 1 μCi (37 kBq) radium dial worn for 16 h/day throughout the year (dose rate 0.375 μSv h(-1)). For this condition we estimated maximum skin dose for our pocket watches as 16 mSv per year, with effective doses of 5.1 mSv and 1.169 mSv when worn in vest and trouser pockets respectively. This assumes exposure from the back of the watch which is generally around 60-67% of that from the front. The maximum skin dose from a wristwatch was 14 mSv, with 4.2 mSv effective dose in vest pocket. Radium ((226)Ra) decays to the radioactive gas radon ((222)Rn), and atmospheric radon concentration measurements taken around a pocket watch in a small sealed glass sphere recorded 18,728 B qm(-3). All watches were placed in a room with a RAD7 real-time radon detector. Radon concentration average was 259±9 Bq m(-3) over 16 h, compared to background average over 24h of 1.02 Bq m(-3). Over 6 weeks highs of the order of 2000 Bq m(-3) were routinely recorded when the heating/ventilation system in the room was operating at reduced rates, peaking at over 3000 Bq m(-3) on several occasions. Estimates of the activity of (226)Ra in the watches ranged from 0.063 to 1.063 μCi (2.31 to 39.31 kBq) for pocket watches and from 0.013 to 0.875 μCi (0.46 to 32.38 kBq) for wrist watches. The risk from old watches containing radium appears to have been largely forgotten today. This paper indicates a health risk, particular to collectors, but with knowledge and appropriate precautions the potential risks can be reduced.

The ability of Helianthus annuus L. and Brassica juncea to uptake and translocate natural uranium and 226Ra under different milieu conditions

Seedlings of Helianthus annuus L. (HA) and Brassica juncea (BJ) were used to test the effect of the pH, the presence of phosphates, and the addition of ethylene-diamine-tetraacetic acid (EDTA) or citrate on the uptake and the translocation of uranium isotopes ((238)U, (235)U, and (234)U) and (226)Ra. The results indicated that the presence of phosphates generally reduces the uptake and transfer of uranium from the roots to the shoots of HA. In the case of BJ, while phosphate enhanced the retention of uranium by roots, the translocation was poorer. Likewise, for (226)Ra, the best translocation was in the absence of phosphates for both species. The addition of citrate increased the translocation of uranium for both species, but had no clear effect on the transfer of (226)Ra. The effect of EDTA was much more moderate both for uranium and for (226)Ra, and for both plant species. Only noticeable was a slightly better uptake of (226)Ra by BJ at neutral pH, although the translocation was lower.