Take a Swipe at Actinide Bioavailability: Application of a New In Vitro Method

Abstract

Filter swipe tests are used for routine analyses of actinides in nuclear industrial, research, and weapon facilities as well as following accidental release. Actinide physicochemical properties will determine in part bioavailability and internal contamination levels. The aim of this work was to develop and validate a new approach to predict actinide bioavailability recovered by filter swipe tests. As proof of concept and to simulate a routine or an accidental situation, filter swipes were obtained from a nuclear research facility glove box. A recently-developed biomimetic assay for prediction of actinide bioavailability was adapted for bioavailability measurements using material obtained from these filter swipes. In addition, the efficacy of the clinically-used chelator, diethylenetriamine pentaacetate (Ca-DTPA), to enhance transportability was determined. This report shows that it is possible to evaluate physicochemical properties and to predict bioavailability of filter swipe-associated actinides.

Fig. 1

Flow diagram of the different steps used to validate an experimental approach for measurement of actinide transfer using material picked up by a filter swipe test.

Fig. 2

Inhalation glove box used for filter swipe tests. The glove box (a) is in three sections—1: Preparation area, 2: Inhalation area for nose-only inhalation, 3: Rat holding tube area (Fig. 2a). Fig. 2b: Swipe held in forceps, Fig. 2c: Filter sealed in bag for glove box exit. Fig. 2d: Interior of preparation showing encircled swipe test surfaces which were Plexiglas (glove box floor (d1, 3 & 5), plastic (bottle cap, box d2 & 6) and PVC (pump connection d5).

Fig. 3

Spectral analysis of filter swipe sample using low background HPGe detector or alpha spectroscopy of filter extracts. Spectral analysis was over the full energy range of the HPGe detector (5 to 1,200 keV) and zooms are shown for the energy ranges of 0-60 keV (Fig 3a) and 68-124 keV (Fig 3b). Figure 3c and d show typical data for alpha spectrometric analyses showing separation of ²³⁹Pu and ²³⁸Pu isotopes as well as ²⁴¹Am. The appropriate peaks of ²⁴²Pu and ²⁴³Am standards are also shown.

Fig. 4

Recovery of Pu from Plexiglass surface using different filter types. An aliquot of a ²³⁹Pu colloidal preparation was pipetted on a Plexiglass support, dried overnight and swiped using filters Versapor, Nuc-Wipes or PTFE as described. Activity was measured in the DMF extract, the Plexiglass support and the initial contamination solution. Swipe recovery (%) = Activity on swipe/initial activity in 50 μl aliquot) × 100; DMF recovery = Activity in DMF/Activity on swipe × 100. Data are the means ± SD for triplicate samples.

Fig. 5

Influence of the presence of filter extract on the transfer behavior of different forms of Plutonium and Americium in the absence and presence of DTPA. Fig. 5a: Gels contained Pu citrate (▲–▲), Pu nitrate (■–■), Pu in colloidal form (◆–◆), or Am nitrate (●–●). Fig. 5b: Gels contained the filter DMF extract of Pu citrate (▲-▲), Pu nitrate (■-■), Pu in colloidal form (◆-◆), or 150-200 Bq of Am nitrate (●-●). The incubation medium contained NaCl (140 mM) and KCl (5 mM) without or with (Fig. 5c and d) DTPA (500 μM). Data are the means ± SD for three replicates and are expressed as a percentage of the recovered activity.

Fig. 6

Activity recovered from different zones of a glove box used for inhalation studies. Fig. 6a: Filter swipe tests were made in the different zones of the glove box using the two filter types. Activity recovered by each filter was counted using the HPGe detector as described. Fig. 6b: The percentage of Am on each filter swipe.

Fig. 7

Levels of activity recovered from different types of surface or surface area or as a function of incubation time in DMF of the filter swipe. Fig. 7a: A: Neoprene glove, B: PVC tube; C: Stainless steel tube; D; End compressed air supply (PVC); E: Forceps-metal. 7b: Different surface areas from 5 to 200 cm² were swiped using the copolymer acrylic filter (Versapor). 7c: Activity recovered after different incubation times in DMF.

Fig. 8

Transfer from static to fluid phase of activity from swipe extracts or different actinide preparations. Fig. 8a: Transfer of total, Pu and Am activity was measured in medium at the different times as described. Pu and Am are expressed as the percentage of the initial total alpha activity. Fig. 8b. For comparison provides swipe sample data (●-●) as well as data for the different forms of Pu, Pu citrate (▲-▲), Pu nitrate (■-■), Pu in colloidal form (◆-◆) as already shown in Fig 5b. In this case Pu obtained from the swipe is expressed as the percentage of the initial Pu in the swipe extract.

Fig. 9

Effect of DTPA on the transfer from static to fluid phase of activity from swipe extracts or Pu in colloidal form. Fig. 9a Transfer of total Pu activity from filter swipe with or without Ca-DTPA (500 μM) in the incubation media. The data are expressed as the fraction of total Pu or Am with respect to the total α activity measured at each time point. Fig. 9b. For comparison provides swipe sample data (○-○) as well as data for Pu in colloidal form (◊-◊) without DTPA (500 μM) and with DTPA (●-●, ◆-◆) as already shown in Fig 5b. In this case Pu obtained from the swipe is expressed as the percentage of the initial Pu in the swipe extract. Data are the means ± SD for triplicate samples.