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[en] The main ring of the Superconducting Super Collider consists of 10 sectors. Each sector has 4 strings and the total nitrogen inventory in a nominal string (4,320 m) is approximately 8,856 kg (2,894 gal). There are occasions when part of the collider nitrogen inventory needs to be vented in an emergency fashion. Due to the large quantity of the nitrogen inventory and the high elevation differential between the below-ground collider ring and the above-ground vent stack, it is essential to vent the nitrogen inventory in the vapor phase. Uninsulated dump tanks are provided at all sites to collect and vaporize liquid nitrogen expelled from the strings. Vapor nitrogen is then vented through a vent stack at surface level into the atmosphere. An emergency venting starts when a remote control valve in the nitrogen subcooler box opens. The string nitrogen inventory is then discharged into the dump tank. Around 100 kg nitrogen inventory will be discharged before the string inventory reaches a saturation state at certain locations. After that, the static heat leak into the 80 K circuit (16,250 W per string) becomes the dominating driving force to expel the nitrogen inventory. Due to the length of the string, the boil-off bubbles are localized. The mass boil-off rate is translated into a much higher mass flow rate expelled from the string. The string saturation pressure is dynamically balanced by the total pressure drop between the string and the vent stack. The capacity requirement for the nitrogen dump tank reaches the maximum when the dump tank at each site has to handle the nitrogen inventory in two strings, which is approximately 17,712 kg (5,788 gal). This work is intended to analyze the volume capacity requirement for the nitrogen dump tanks for this worst scenario. A computer program is developed to numerically simulate the emergency venting process. The string, dump tank, and venting paths are modeled individually and then linked to impose the constraints
[en] The current situation of ventilation system in a uranium mine is introduced, the reasons of radon pollution in the uranium mine is analyzed, and the technical measures of controlling radon pollution are put forward. After the adjustment of the mine ventilation system, the effects of ventilation and attenuating radon concentration are obvious. (authors)
[en] An adequate ventilation system is needed for air quality and handling in a mine and is comprised of many different pieces of equipment for removing contaminated air and supplying fresh air and thereby provide a satisfactory working environment. This manual highlights auxiliary ventilation systems made up of small fans, ducts, tubes, air movers, deflectors and additional air flow controls which distribute fresh air delivered by the primary system to all areas. A review of auxiliary ventilation is provided. Design, operation and management issues are discussed and guidelines are furnished. This manual is limited to underground hard rock operations and does not address directly other, specific auxiliary systems, either in underground coal mines or uranium mines.
[en] RSV-infected children demonstrate various radiographic features, some of which are associated with worse clinical outcomes. To investigate whether specific chest radiological patterns in RSV-infected children with acute respiratory failure (ARF) in the peri-intubation period are associated with prolonged duration of mechanical ventilation. We included RSV-infected children <1 year of age admitted with ARF from 1996 through 2002 to the pediatric intensive care unit at Massachusetts General Hospital. Their chest radiographs were evaluated at three time-points: preintubation (day -1) and days 1 and 2 after intubation. Univariate and multiple logistic regressions models were utilized to investigate our objective. The study included 46 children. Using day 1 chest radiograph findings to predict duration of mechanical ventilation of >8 days, a backward stepwise regression arrived at a model that included age and right and left lung atelectasis. Using day 2 chest radiograph results, the best model included age and left lung atelectasis. A model combining the two days' findings yielded an area under the ROC curve of 0.92 with a satisfactory fit (P = 0.95). Chest radiological patterns around the time of intubation can identify children with RSV-associated ARF who would require prolonged mechanical ventilation. (orig.)
[en] This design feature (DF) is intended to evaluate the effects of continuous ventilation in the emplacement drifts during preclosure and how the effects, if any, compare to the Viability Assessment (VA) reference design for postclosure long term performance. This DF will be evaluated against a set of criteria provided by the License Application Design Selection (LADS) group. The VA reference design included a continuous ventilation airflow quantity of 0.1 m3/s in the emplacement drifts in the design of the repository subsurface facilities. The effects of this continuous ventilation during the preclosure was considered to have a negligible effect on postclosure performance and therefore is not included during postclosure in the assessment of the long term performance. This DF discusses the effects of continuous ventilation on the emplacement drift environment and surrounding rock conditions during preclosure for three increased airflow quantities. The three cases of continuous ventilation systems are: System A, 1.0 m3/s (Section 8), System B, 5.0 m3/s (Section 9), and System C, 10.0 m3/s (Section 10) in each emplacement drift split. An emplacement drift split is half total length of emplacement drift going from the east or west main to the exhaust main. The difference in each system is the quantity of airflow in the emplacement drifts
[en] Mine ventilation is the most important way of reducing radon in uranium mines. At present, the radon and radon progeny levels in Chinese uranium mines where the cut and fill stoping method is used are 3–5 times higher than those in foreign uranium mines, as there is not much difference in the investments for ventilation protection between Chinese uranium mines and international advanced uranium mines with compaction methodology. In this paper, through the analysis of radon reduction and ventilation systems in Chinese uranium mines and the comparison of advantages and disadvantages between a variety of ventilation systems in terms of radon control, the authors try to illustrate the reasons for the higher radon and radon progeny levels in Chinese uranium mines and put forward some problems in three areas, namely the theory of radon control and ventilation systems, radon reduction ventilation measures and ventilation management. For these problems, this paper puts forward some proposals regarding some aspects, such as strengthening scrutiny, verifying and monitoring the practical situation, making clear ventilation plans, strictly following the mining sequence, promoting training of ventilation staff, enhancing ventilation system management, developing radon reduction ventilation technology, purchasing ventilation equipment as soon as possible in the future, and so on.
[en] The status of mine development, ventilation system and ventilation management in Caotaobei uranium mine is introduced, and problems existing in the ventilation system are pointed out, including enter-air pollution, air leaking, large air resistance. The special improvement scheme involved with technique and management are proposed for problems. After implementation of the scheme, the effective utilization of air volume has been greatly enhanced, and the allocation of air volume is reasonable. The acceptability rate of radon and its daughter concentrations has risen from 12.5% before implementation of the scheme to 88.9%. (authors)
[en] This engineering note describes how exhaust fan 6 (EF-6) and exhaust fan 7 (EF-7) are controlled and monitored. Since these two fans are a vital link in the ODH safety system, they will be monitored, controlled and periodically operated by the programmable logic controller (PLC). If there should be a fault in the ventilation system, the PLC will print a warning message to the cryo control room printer and flash a descriptive warning on the ODH/ventilation graphics page. This fault is also logged to the Xpresslink graphics alarm page and to an alarm history hard disk file. The ventilation failure is also an input to the auto dialer which will continue it's automatic sequence until acknowledged. EF-6 delivers 13000 C.F.M. and is considered emergency ventilation. EF-7 delivers 4500 C.F.M. and will run 24 hrs a day. Both ventilation fans are located in an enclosed closet in the TRD gas room. Their ductwork, both inlets and outlets run along side the pipe chase, but are separated by an airtight wall. Their combination motor control starter cabinets are located in the TRD room in plain visible sight of the fans with the closet door open. The fans have signs that state they are automatically controlled and can energize at any time.
[en] Essential factors and characteristics of ventilation systems in underground uranium mines are introduced. In order to match the ventilation requirements of radon reduction and dust discharge, the methods and measures of ventilation systems optimization are analyzed. By means of optimum system disposal, ventilation power expenses can be reduced, and better economic and environmental benefits can be acquired. (authors)