Isotope process

Some of these processes also cause measurable isotopic effects. Evaporation into empty space can cause the residual liquid or solid to become enriched in heavy isotopes. Processes that do not necessarily produce chemical fractionations can also produce isotopic effects. Diffusion is an example of such a process. Also, if the various constituents that go into making asteroids and planets have different isotopic compositions, the formation of these bodies can result in bulk compositions that are isotopically fractionated. Oxygen isotopes... 

Figure 1 Schematic representation of various isotopic processes shown on an oxygen three-isotope plot. Almost aU terrestrial materials plot along a line of fractionation most primitive meteoritic materials plot near a line of 0 addition. ...

Hot fluids readily dissolve and transport material, both in hydrothermal systems (see Chapter 3.15) and in deeper metamorphic environments (see Chapter 3.06). If such fluids are isotopically distinct, then stable isotopes can help define fluid-rock reactions. Isotopic processes at deeper levels are likely to be rather subtle, because temperatures are high, timescales are long, and different oxygen reservoirs may not be very distinct isotopically. Therefore, isotopic studies of contact metamorphism provide some of the best examples of the mechanisms by which fluids and rocks interact and exchange oxygen. 

This chapter focuses upon some recent observations of mass-independent isotopic processes in nature. As discussed by Thiemens et al. (2001) and Thiemens (2002), there exist other mass-independent isotope effects in nature that derive from non-ozone reactions. For example, CO2 photolysis produces a large mass-independent isotope effect that, in part, may account for observations in the SNC (martian) meteorites and the synthesis of their secondary minerals. UV photolysis of SO2 produces new isotopic fractional effect. An accompanying mass-independent isotopic composition determines the evolution of oxygen in the Earth s earliest atmosphere. 

The focus in this review is on water isotopes in present-day precipitation and in paleoprecipita-tion. From an isotopic point of view, understanding and modeling isotopic processes as they occur in clouds, where precipitation is formed, is key to link the growth of individual elements to global-scale distributions. The complexity of cloud isotopic processes depends on the type of cloud considered. 

Isotopic Processes in the Upper (Bioturbated) Sediment Regime. 7.3 Isotopic Processes in the Deeper Diffusion-dominated Sediment Regime ANCIENT MARINE SEDIMENTS... 

Isotopic Processes in the Upper (Bioturbated) Sediment Regime... 

Isotopic composition of individual elements in the natural media may noticeably change. These changes in water composition are considered to be isotopic processes. Three main reasons may be identified, which cause change in elements isotopic composition in natural water radioactive decay of elements themselves, fractionating of their atoms in mass transfer and mixing their atoms of different isotopic composition. 

Primary Hazard Screening documentation for HCF isotope processing of Sandia Nationai Laboratories Integrated Safety Management System (SNL7A00124-001) ... 

For the purpose of hazard evaluation, activities associated with HCF isotope processing are grouped into the following operations ... 

Removal of isotope process radioactive waste from the waste storage area (Room 109) or any subsequent handling of such waste,... 

Because the HCF conducts primarily repetitive, isotope processing activities, the specific hazards can be readily identified as corresponding to the activities, materials, facilities, and equipment of the separation process for medical isotopes. Specific hazards were analyzed by the operation, process, and location involved. Handling and processing of various isotopes will have similar hazards that can also be characterized and evaluated against those described in this SAR. 

The basement area of Building 6580 with isotope processing locations and waste storage area 2... 

At least one bounding accident from each of the major types has been selected unless the bounding consequences are low. Accident categories are internally initiated operational accidents (fires, explosions, spills, and criticality) natural phenomena events for the site (e.g. earthquakes, tornadoes) that could affect the facilify and externally initiated, man-made events (e.g. airplane crashes, transportation accidents, and adjacent facility events). Criticality assessments have indicated that criticality is an incredible event for isotope processing operations. Based on these evaluations, criticality has not been included in the hazard analysis and will not be included in the accident analysis. 

The above assumption with regard to materiai at risk wiil be overly conservative in most process scenarios for the less volatile fission products by two to four orders of magnitude, but this will be only about a factor of four in terms of potential total dose consequences, as depicted later in Table 3.4-1. However, this assumption will encompass future unanticipated processing scenarios which might render the less volatile inventory more available for release. Based on this assumption, the hazard and accident analyses are not dependent on any specific isotope processing steps, since there are no process operations which could render the material more volatile. Thus, these process operations are not relied on to mitigate any release consequences and therefore do not perform any Safety Function. 

Most of the time (i.e. at times other than during active isotope processing) process stations wili contain only residual quantities of radiologicai materiais. 

During normai operations, isotope processing will be in-progress a significant fraction of the time, however the amount of radiologicai materiais avaiiabie for release are limited by the quantity and form of the material in process. 

The Zone 2A canyon and Room 109 physical structures encompass all HCF isotope processing and radioactive waste handling operations. These structures serve three safety-related purposes (1) to provide structural integrity and protection against the elements, (2) to provide radiation shielding for normal, abnormal, and accident conditions, and (3) to confine radioactive-material under normal, abnormal, and accident conditions. These structures serve no other functions that meet safety-related criteria. 

Steel confinement boxes (located inside the Zone 2A canyon) serve as passive defense in depth barriers to the potential uncontrolled movement of radioactive materials from isotope processing activities under normal and abnormal conditions. These SCBs serve no other functions that meet safety-related criteria. 

The Zone 1 and Zone 2A ventilation exhaust ducting and HEPA and charcoal filters are passive components. Their safety-related function is performed continuously while the HCF ventilation system is in operation. When the ventilation system is not operating, no isotope processing operations are being conducted, and any residual radioactive materials are in nonvolatile states and are confined within the SCBs and Zone 2A canyon. Thus, the functional requirements applicable to the filters are ... 

Criterion 4 is not applicable to isotope processing operations and must be applied on a case-by-case basis by means of the USQ process as "experimental conditions" are proposed. 

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