Reading tea leaves worldwide: decoupled drivers of initial litter decomposition mass-loss rate and stabilisation

The breakdown of plant material fuels soil functioning and biodiversity. Currently, process understanding of global decomposition patterns and the drivers of such patterns are hampered by the lack of coherent large-scale datasets. We buried 36,000 individual litterbags (tea bags) worldwide and found an overall negative correlation between initial mass-loss rates and stabilization factors of plant-derived carbon, using the Tea Bag Index (TBI). The stabilization factor quantifies the degree to which easy-to-degrade components accumulate during early-stage decomposition (e.g. by environmental limitations). However, agriculture and an interaction between moisture and temperature led to a decoupling between initial mass-loss rates and stabilization, notably in colder locations. Using TBI improved mass-loss estimates of natural litter compared to models that ignored stabilization. Ignoring the transformation of dead plant material to more recalcitrant substances during early-stage decomposition, and the environmental control of this transformation, could overestimate carbon losses during early decomposition in carbon cycle models

Distribution of Balsamorhiza rosea in Rattlesnake Hills with respect to various environmental factors

Balsamorhiza rosea (Compositae), a suffrutescent perennial, is found on several rocky hilltops with sparse canopy cover in Eastern Washington. This study investigated B. rosea's abundance and its associated species along several physical gradients. Important elements of microclimate selected for this analysis were elevation, slope aspect, slope angle, and soil depth. Results show that the occurrence of B. rosea is associated more strongly with soil depth than with other factors examined. The distribution of B. rosea was not fully explained by the factors in this study. Other potential factors determining its distribution are discussed

Combination TLD/TED dose assessment

During the early 1980s, an appraisal of dosimetry programs at US Department of Energy (DOE) facilities identified a significant weakness in dose assessment in fast neutron environments. Basing neutron dose equivalent on thermoluminescence dosimeters (TLDS) was not entirely satisfactory for environments that had not been well characterized. In most operational situations, the dosimeters overrespond to neutrons, and this overresponse could be further exaggerated with changes in the neutron quality factor (Q). Because TLDs are energy dependent with an excellent response to thermal and low-energy neutrons but a weak response to fast neutrons, calibrating the dosimetry system to account for mixed and moderated neutron energy fields is a difficult and seldom satisfactory exercise. To increase the detection of fast neutrons and help improve the accuracy of dose equivalent determinations, a combination dosimeter was developed using TLDs to detect thermal and low-energy neutrons and a track-etch detector (TED) to detect fast neutrons. By combining the albedo energy response function of the TLDs with the track detector elements, the dosimeter can nearly match the fluence-to-dose equivalent conversion curve. The polymer CR-39 has neutron detection characteristics superior to other materials tested. The CR-39 track detector is beta and gamma insensitive and does not require backscatter (albedo) from the body to detect the exposure. As part of DOE's Personnel Neutron and Upgrade Program, we have been developing a R-39 track detector over the past decade to address detection and measurement of fast neutrons. Using CR-39 TEDs in combination with TLDs will now allow us to detect the wide spectrum of occupational neutron energies and assign dose equivalents much more confidently

Steam generator group project progress report. Task 3, health physics

The gamma radiation fields in and around the retired Surry steam generator were measured extensively with thermoluminescent dosimeters (TLD's) and other standard radiation instruments. The techniques of measurement and the results are described for locations outside the shell, inside the channel head, and inside the secondary side of the steam generator. The gamma fields ranged from more than 10 R/hr in the middle of the tube bundle on the secondary side to less than 5 mR/hr at the bottom of the outside of the shell below the channel head. Co-60 was the only detected gamma emitter. The results of the measurements were used in an analytical model which predicted the Co-60 inventory to be between 70 and 87 curies

Potential behavior of depleted uranium penetrators under shipping and bulk storage accident conditions

An investigation of the potential hazard from airborne releases of depleted uranium (DU) from the Army's M829 munitions was conducted at the Pacific Northwest Laboratory. The study included: (1) assessing the characteristics of DU oxide from an April 1983 burn test, (2) postulating conditions of specific accident situations, and (3) reviewing laboratory and theoretical studies of oxidation and airborne transport of DU from accidents. Results of the experimental measurements of the DU oxides were combined with atmospheric transport models and lung and kidney exposure data to help establish reasonable exclusion boundaries to protect personnel and the public at an accident site. 121 references, 44 figures, 30 tables

Radiological assessment of steam generator repair and replacement

Previous analyses of the radiological impact of removing and replacing corroded steam generators have been updated based on experience at Surry Units 1 and 2 and Turkey Point Units 3 and 4. The sleeving repairs of degraded tubes at San Onofre Unit 1, Point Beach Unit 2, and R.E. Ginna are also analyzed. Actual occupational doses incurred during application of the various technologies used in repairs have been included, along with radioactive waste quantities and constituents. Considerable progress has been made in improving radiation protection and reducing worker dose by the development of remotely controlled equipment and the implementation of dose reduction strategies that have been successful in previous repair operations