PubMed · 9003721
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
L G Weinstock. 1997. NESHAP risk assessment.. https://pubmed.ncbi.nlm.nih.gov/9003721/
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
A new winter and summer investigation of radon concentrations in parts of the Ogof Ffynnon Ddu system at Penwyllt, South Wales, has been carried out using 100 environmental National Radiological Protection Board track etch detectors. Fifty detectors were installed in the system in December 1998 and again in August 1999 for a period of a month. The data obtained confirm that the system has moderately high radon concentrations with a system mean of 2318 Bq m(-3) in winter and 2844 Bq m(-3) in summer. Traverse means have a summer high of 3094 Bq m(-3) for OFDI to Cwm Dwr and a winter low of 1946 Bq m(-3). The extremely high concentrations approaching 20,000 Bq m(-3), reported previously from the system (Hyland, 1995), have not been reproduced. The data show that the airflow directions at the entrances are not what might have been predicted. Air appears to be largely continuously emerging from the lowest entrance but, at the higher entrances, conversely to the predictions, in winter air enters and in summer appears to be coming out or is variable. Internally, there are sites that in winter have very low radon concentrations that can only be explained by the ingress of fresh air. These are not matched in the summer experiment, again indicating that ingress of fresh air to some parts of the system is very variable. The data illustrate the complexity of airflow within a multi-entrance system but behind these variations several mean concentrations can be obtained from which an approximation of the dose likely to be received can be calculated. Using the maximum mean concentration obtained, 3094 Bq m(-3), and using the latest dose conversion, a 10 h underground trip in the Ogof Ffynnon Ddu system yields a calculated dose of 0.12 mSv. Given that the recommended limit for a member of the public is 1 mSv, this dose would be reached after about 80 h of caving in the system.
Continental margins are important areas to be considered when studying the distributions and depositions of pollutants, both conventional and radioactive. Coastal sediments accumulate most of those contaminants which can be introduced following atmospheric and/or fluvial pathways. Moreover, their residence times within the water column are usually shortened due to their affinity to associate with the downward falling particulate matter, more abundant at shallower depths. In this paper the distribution profiles and inventories of plutonium, americium and cesium are detailed, providing useful information about recent sedimentation phenomena such as sediment mixing, slumping processes and bioturbation. Unsupported 210Pb data are used as reliable indicators of enhanced/reduced deposition events. Also, the calculated inventories have enabled the estimation of the radiological contribution of the Spanish Mediterranean margin to the total radioactivity deposited onto the Mediterranean sea floor.
14C specific activities, above ambient background levels, were determined in individual treerings (corresponding to the years 1950-1999) sectioned from an oak tree that was felled in autumn 1999, from a location 1.5 km east of the Sellafield nuclear fuel reprocessing plant in Cumbria. north-west England. The data were used to produce a new, improved, reconstruction of Sellafield's annual atmospheric 14C discharges between 1951 and 1999, using the most reliable discharge data set (1994-1999) as the primary basis for the determination of a new calibration factor that relates excess 14C activity in individual tree rings to the annual discharge during the corresponding year. The results indicate that the current British Nuclear Fuels plc (BNFL) estimate of total 14C discharges to the atmosphere prior to 1978 is significantly overestimated, while the current estimate of total 14C discharges after 1978 is very similar to that determined in this study. In this study, the total activity of 14C discharged to the atmosphere from Sellafield between 1951 and 1999 is estimated to be 259+/-63 TBq (at 2 std. dev.). The BNFL current estimate is 360TBq.