Neptunium(iv)-hydroxamate complexes: their speciation, and kinetics and mechanism of hydrolysis.

Simple hydroxamic acids such as acteohydroxamic acid (AHA) have been identified as suitable reagents for the control of Pu and Np in advanced separation processes for nuclear fuel reprocessing such as the Advanced PUREX or UREX based recycle processes, due to their ability to strip the tetravalent form of Pu and Np from tri-butyl phosphate into nitric acid. However, both free and metal bound hydroxamates are known to undergo acid catalysed hydrolysis at low pH, the kinetics of which must be characterised before implementation of PUREX/UREX based reprocessing flowsheets. In support of this implementation, a comprehensive thermodynamic and kinetic model that describes both the complex speciation and hydrolysis of AHA in the presence of Np(iv) has been developed. The model has two unique features: (i) in the case of the hydrolysis reaction kinetics, the model includes the hydrolysis of not only free AHA but also both the mono- and bishydroxamato-Np(iv) complexes; (ii) for the associated speciation calculations, the model explicitly includes the ionic strength dependence of not only the mono- and bishydroxamato-Np(iv) complexes but also the mono- and bisnitrato neptunium(iv) and monohydroxoneptunium(iv) complexes. For the latter three species, respective SIT coefficients of Δε1,NO3 = -0.13 ± 0.03 kg mol-1, , Δε2,NO3 = -0.37 ± 0.13 kg mol-1, Δε1,OH = -0.36 kg mol-1 and log10 K01,OH = -1.23 were also determined. Using experimental data from a series of kinetic studies on the Np(iv)-AHA system, this model has been used to determine the rate constants for hydrolysis of mono- and bis-acetohydroxamatoneptunium(iv) at 25 °C for the first time. These were found to be 3.5 × 10-5 ± 2.5 × 10-5 dm3 mol-1 s-1 and 1.9 × 10-3 ± 1.3 × 10-3 dm3 mol-1 s-1, respectively. Comparison of these values with the rate constants for hydrolysis of free AHA indicates that complexation of AHA with Np(iv) increases the rate of hydroxamate hydrolysis - an observation that we attribute to the electron withdrawing effect of the metal centre within the Np(iv)-AHA complex increasing the susceptibility of the AHA carbonyl carbon to nucleophilic attack, the accepted first step in its mechanism of hydrolysis.

A new Certified Reference Material for radionuclides in Irish sea sediment (IAEA-385).

A new Certified Reference Material (CRM) for radionuclides in sediment (IAEA-385) is described and the results of the certification process are presented. Eleven radionuclides ((40)K, (137)Cs, (226)Ra, (228)Ra, (230)Th, (232)Th, (234)U, (238)U, (238)Pu, (239+240)Pu and (241)Am) have been certified and information mass activities with 95% confidence intervals are given for seven other radionuclides ((90)Sr, (210)Pb((210)Po), (235)U, (239)Pu, (240)Pu and (241)Pu). Results for less frequently reported radionuclides ((60)Co, (99)Tc, (134)Cs, (155)Eu, (224)Ra and (239)Np) and information on some activity and mass ratios are also reported. The CRM can be used for quality assurance/quality control of the analysis of radionuclides in sediment samples, for the development and validation of analytical methods and for training purposes.

ETCare: a randomized, controlled, masked trial comparing two solutions for upper airway care in the NICU.

BACKGROUND: Small quantities of normal saline are sometimes instilled into the endotracheal tube of intubated neonates, to assist with the removal of thick secretions and maintain patency of the endotracheal tube. However, saline is detrimental to the innate immune system of the upper airway mucosa, rapidly unfolding and inactivating antimicrobial peptides such as LL-37. We previously reported the preparation and feasibility testing of 'ETCare', a low-sodium, physiologically based solution for airway care, and we now report results of a randomized, masked, controlled, two-centered study testing ETCare vs sterile saline among 60 intubated NICU patients. STUDY DESIGN: Sixty intubated NICU patients were randomized to having their airway care with ETCare vs saline. Three hypotheses were tested: (1) tolerance - patients will tolerate ETCare for airway care as well as they tolerate saline, (2) nosocomial infections - ETCare will result in fewer tracheal aspirates where organisms grow and fewer cases of nosocomial sepsis, and (3) chronic lung disuse - ETCare will result in fewer patients discharged home on supplemental O2. RESULTS: Thirty NICU patients with an endotracheal tube in place were randomized to receive their airway care with ETCare, and 30 to receive their care with saline. Only the pharmacist was aware of the randomization; the two solutions were visually indistinguishable and were dispensed in identical syringes. Tolerance of the solutions was similar. The ETCare recipients had trends toward fewer positive blood cultures (odds ratios (OR), 0.48; 95% confidence interval (CI), 0.13 to 1.68), and fewer discharges home on supplemental O2 (OR, 0.43; 95% CI, 0.14 to 1.32; P=0.075). CONCLUSIONS: On the basis of this study and our previous 10-patient feasibility trial, we maintain that, for airway care, intubated NICU patients tolerate ETCare as well as saline. Data from this study can be used in estimating the sample sizes needed for a phase III trial. We speculate that such a trial will demonstrate that, compared with saline, ETCare will result in fewer nosocomial infections and less chronic lung disease.

Avoiding endotracheal intubation of neonates undergoing laser surgery for retinopathy of prematurity.

OBJECTIVE: Respiratory support of neonates during and following laser surgery for retinopathy of prematurity (ROP) is commonly accomplished using endotracheal intubation and mechanical ventilation. However, most patients undergoing ROP surgery have been weaned off mechanical ventilation days or weeks before the surgery. When they are electively re-intubated for ROP surgery, it can be difficult to extubate them postoperatively. One of the three level III neonatal intensive care units (NICUs) in the Intermountain Healthcare system initiated a program of using nasopharyngeal prongs, rather than endotracheal intubation, for respiratory support during ROP surgery. METHODS: We performed an historic cohort analysis of all neonates undergoing ROP surgery during their NICU stay at the three level III NICU's between 1 January 2002 and 31 March 2006. Data collected included birth weight, gestational age at delivery and corrected gestational age at ROP surgery, whether or not they were intubated in the days immediately preceding the ROP surgery, whether or not they were electively intubated for the ROP surgery, the respiratory modality used during and the 3 days following ROP surgery, and all blood gas determinations and respiratory charges during this period. RESULTS: Fifty-four patients underwent ROP surgery during this period. All 23 from NICUs 'A' and 'B' had endotracheal intubation for surgery, while in NICU 'C' 24 were managed using nasopharyngeal prongs. The birth weights of those intubated for surgery (661+/-180 g, mean+/-s.d.) were similar to those not intubated (732+/-180 g). Similarly, the gestational age at birth did not differ between those intubated for surgery (25.2+/-1.3 week) and those not (25.6+/-2.1 week). The day following surgery, 77% (23/30) of those who had been intubated for surgery remained intubated and on mechanical ventilation, whereas only one (4%) of those not intubated for surgery was intubated in the postoperative period (P<0.001). On day 3 following surgery, 50% (15/30) of those intubated for surgery remained intubated and on mechanical ventilation, whereas none of those not intubated for surgery were intubated (P<0.001). Management with nasopharyngeal prongs did not result in higher PCO(2)s, or lower pH values, during or after surgery. Respiratory charges for the 3 days following surgery were 1762+/-678 dollars (mean+/-s.d.)/patient among those intubated versus 357+/-352 dollars/patient for those managed with nasopharyngeal prongs (P<0.001). CONCLUSIONS: Neonates undergoing laser surgery for ROP can often be supported intraoperatively and postoperatively using nasopharyngeal prongs, thus avoiding the need for endotracheal intubation.

Comparing two methods of delivering high-flow gas therapy by nasal cannula following endotracheal extubation: a prospective, randomized, masked, crossover trial.

OBJECTIVE: We compared two methods of delivering high-flow gas therapy by nasal cannula, applied immediately after planned endotracheal extubations of NICU patients. STUDY DESIGN AND METHODS: Thirty NICU patients who were about to be extubated from mechanical ventilation were randomized into two groups; Group 1 received Vapotherm for the first 24 h after extubation, then standard high-flow nasal cannula for the next 24 h, and Group 2 received standard high-flow therapy for the first 24 h, then Vapotherm for the next 24 h. At 24 h after extubation and again 48 h after extubation, a neonatologist who was not aware which modality the patient had been receiving examined the nasal mucosa and applied a scoring system. A research nurse who was unaware of the modality abstracted respiratory rates and respiratory effort scores from a specific study-bedside record. The experimental design was such that a patient could 'fail' extubation either by reintubation for mechanical ventilation, or by rescue to the opposite modality before completing the 24-h test period. RESULTS: Fifteen patients were randomized to Group 1 and 15 to Group 2. No differences were apparent between the groups in birth weight, gestational age, age at study entry, gender or underlying pulmonary disorder. Respiratory rates were similar while on Vapotherm (52+/-13 breaths/min, mean+/-s.d.) and high-flow (54+/-14/min). At 24 h after starting the modality, those on Vapotherm had more normal examinations of the nasal mucosa (2.7+/-1.2 vs 7.8+/-1.7, P < 0.0005) and lower respiratory effort scores (1.2+/-0.6 vs 2.0+/-0.9, P < 0.05) than did those on high-flow. No patients failed while on Vapotherm, but seven failed while on high-flow (two reintubations and five rescue switches to Vapotherm, P < 0.005). CONCLUSIONS: Among NICU patients immediately following extubation, Vapotherm performed better than a standard high-flow nasal cannula in maintaining a normal appearing nasal mucosa, a lower respiratory effort score, and averting reintubation.

Tissue changes resulting from the injection of gamma-irradiated cells into the gynogenetic teleost, Poecilia formosa.

In previous studies a clone of the gynogenetic fish, Poecilia formosa (the Amazon molly), was successfully used as a test animal to identify ultraviolet-induced damage. This work has been extended, and the fish system was used to detect damage caused byionizing radiation. Fish cells, exposed in vitro to 250 and 500 rads, were injected into young isogenic recipients, and 9 months later the fish were examined grossly and histologically. Two of the most conspicuous changes that resulted were the development of extensive invasive thyroid hyperplasia and hypertrophy body, with an apparent reduction in the amount of hemato-poietic tissue in the head kidney and spleen. We discuss the difference between the responses of the recipient fish to cells exposed to ionizing radiation and to cells exposed to ultraviolet light.

The radiation exposure of black-headed gulls (Larus ridibundus) in the Ravenglass Estuary, Cumbria, U.K.: a preliminary assessment.

A variety of fission-product and transuranic radionuclides originating from the marine discharges from the fuel reprocessing plant at Sellafield, Cumbria are detectable in the bodies of black-headed gulls and their environment in the Ravenglass Estuary approximately 10 km to the south-west of the plant. The maximum concentrations of 95Nb, 137Cs and 239/240Pu detected in body tissues lie in the range 2 X 10(-3) to 1.5 X 10(-2) Bqg-1 wet weight. Many more radionuclides are detected in the regurgitated pellets and faeces produced by the gulls and have higher concentrations in the range 7 X 10(-3) to 1.7 Bqg-1 wet weight. The radionuclide contamination of the sediment produces a source of enhanced external gamma-ray exposure which can be measured directly. The available data on distributions and concentrations of radionuclides have been combined with simple dosimetry models to provide estimates of the radiation exposure of the birds. The total whole body dose rate to the adult birds from the contaminant radionuclides is approximately ten times that from the natural radiation background, while that to the developing eggs is approximately four times the natural background. The potential radiation exposure of the cells lining the alimentary tract could be much higher when contaminated food is in transit, but the long-term average exposure in this case is subject to uncertainty. The limited data on the effects of radiation exposure on birds do not indicate any response at dose rates below one hundred times that from the natural radiation background.(ABSTRACT TRUNCATED AT 250 WORDS)

A system for protecting the environment from ionising radiation: selecting reference fauna and flora, and the possible dose models and environmental geometries that could be applied to them.

In order to demonstrate, explicitly, that the environment can be protected with respect to controlled sources of ionising radiation, it is essential to have a systematic framework within which dosimetry models for fauna and flora can be used. And because of the practical limitations on what could reasonably be modelled and the amount of information that could reasonably be obtained, it is also necessary to limit the application of such models to a 'set' of fauna and flora within a reference' context. This paper, therefore, outlines the factors that will need to be considered to select such 'reference' fauna and flora, and describes some of the factors and constraints necessary to develop the associated dosimetry models. It also describes some of the most basic environmental geometrics within which the dose models could be set in order to make comparisons amongst different radiation sources.

Rates of accumulation of dieldrin by a freshwater filter feeder: Sphaerium corneum.

The rate of dieldrin accumulation by Sphaerium corneum was determined in the field and under controlled conditions in the laboratory. The methods gave comparable results and it was established that Sphaerium attained an equilibrium concentration of dieldrin in its tissues in a short time period and exhibited a bioaccumulation factor of 1000. The rate of dieldrin accumulation by direct uptake from dieldrin in solution was compared to the rate obtained for indirect uptake from dieldrin adsorbed onto particulate material. The primary route of dieldrin uptake into Sphaerium was shown to be by direct partitioning of residues into lipoidal tissues from water. The effect of temperature on the rate of accumulation was also studied. The rate of accumulation increased with temperature in the range 5 degrees C to 20 degrees C. The frequency of gill cilia beat in relation to accumulation rate was studied in this temperature range and a correlation is shown.

Alpha-emitting, hot particles in Irish sea sediments.

Alpha-emitting, hot particles have been observed in samples of liquid effluent from the nuclear fuel reprocessing plant at Sellafield, U.K. Similar particles, thought to originate from Sellafield, have been found in environmental samples from sites near the plant. The occurrence and distribution of hot particles in surface sediments from the northeastern sector of the Irish Sea are described and the implications for predicting transuranium element behaviour are discussed.

International Arctic Seas Assessment Project.

The International Atomic Energy Agency responded to the news that the former Soviet Union had dumped radioactive wastes in the shallow waters of the Arctic Seas, by launching the International Arctic Seas Assessment Project in 1993. The project had two objectives: to assess the risks to human health and to the environment associated with the radioactive wastes dumped in the Kara and Barents Seas; and to examine possible remedial actions related to the dumped wastes and to advise on whether they are necessary and justified. The current radiological situation in the Arctic waters was examined to assess whether there is any evidence for releases from the dumped waste. Potential future releases from the dumped wastes were predicted, concentrating on the high-level waste objects containing the major part of the radionuclide inventory of the wastes. Environmental transport of released radionuclides was modelled and the associated radiological impact on humans and the biota was assessed. The feasibility, costs and benefits of possible remedial measures applied to a selected high-level waste object were examined. Releases from identified dumped objects were found to be small and localised to the immediate vicinity of the dumping sites. Projected future annual doses to members of the public in typical local population groups were very small, less than 1 microSv--corresponding to a trivial risk. Projected future doses to a hypothetical group of military personnel patrolling the foreshore of the fjords in which wastes have been dumped were higher, up to 4 mSv/year, which still is of the same order as the average annual natural background dose. Moreover, since any of the proposed remedial actions were estimated to cost several million US$ to implement, remediation was not considered justified on the basis of potentially removing a collective dose of 10 man Sv. Doses calculated to marine fauna were insignificant, orders of magnitude below those at which detrimental effects on fauna populations might be expected to occur. Remediation was thus concluded not to be warranted on radiological grounds.

Marine radioactivity assessment of Mururoa and Fangataufa atolls.

The International Atomic Energy Agency (IAEA) carried out an international project. 'The Study of the Radiological Situation at the Atolls of Mururoa and Fangataufa' with the aim of assessing the present and future radiological situation at the atolls and making recommendations for either monitoring or remedial actions if they are deemed necessary. The paper concentrates on marine radioactivity aspects and gives an estimation of present radionuclide concentrations in water, sediment and biota of the Mururoa and Fangataufa lagoons and the surrounding ocean. The dominant radionuclide in both lagoons is Pu in sediments (the total inventory is approximately 30 TBq). A decline in radionuclide concentrations has been observed in recent years in lagoon water, with the exception of 3H and 90Sr, for which a contribution from underground sources is to be expected. Radionuclide concentrations in biota from the lagoons and the surrounding ocean are low and consistent with previous measurements. The observed radionuclide concentrations in both lagoons imply that no radiological risk exists for hypothetical inhabitants of Mururoa and Fangataufa Atolls.

A possible approach for the assessment of radiation effects on populations of wild organisms in radionuclide-contaminated environments?

It is frequently asserted that measures to protect the biotic environment from increased radiation exposures arising from human activities should be focussed on the population rather than the individual. It is, however, difficult (if not impossible) to identify any population-specific attributes that can be affected by radiation exposure directly rather than through the mediation of direct, known and identifiable effects in individual organisms. Indeed, it is often conceded that this difficulty forces attention to be refocussed onto the effects in individuals. Regulatory controls on radioactive waste management and disposal could then be implemented to ensure that any radiation effects in individual native plants and animals remain at, or below, some acceptable level (yet to be defined). Nevertheless, the question remains as to whether such controls would also provide for the protection of the population. An answer to this question depends on the availability of a model that allows the integration of the known effects of radiation exposure on the mortality, morbidity, fertility and fecundity of individuals into an assessment of the possible impact at the population level. The utility of one such approach, the Leslie Matrix Model, is explored in respect of a fish population (the plaice, Pleuronectes platessa). This initial implementation of the population model is simplistic (and, certainly, environmentally unrealistic), but it is concluded that the output from the model does provide some insights into how the population might respond to radiation-induced changes in individual attributes, and that further development in the direction of increased realism is fully warranted.