Long-term reactivity

Fig. 5.32. Photographs of double magnetron planar (a) and rotatable (b) targets after long-term reactive sputtering of ZnO Al. The planar target is shown after 1,850kWh, the rotatable target after 11,500kWh (source Von Ardenne Anlagen-technik, Dresden)...

Characterization of long-term reactivity and bioavailability of heavy metals in sediments can be performed by (i) acid-producing potential (APP Kersten and Fbrstner... 

Passivation of iron granulates in permeable barriers used for in situ groundwater remediation may result in a shorter life time and in contaminant breakthrough earlier than expected. Therefore, mineral reactions or generally the effect of other groundwater constituents on the long term reactivity of iron is of major interest for the application of this technology in environmental clean up. For interpretation of column experiments it is also important to estimate the effect of flow velocity on the extent of passivation due to mineral reactions. 

Control rods are used primarily for power distribution shaping and for shim control of long-term reactivity changes, which occur as a result of fuel irradiation. The flow control function, which is used to follow rapid load changes, reduces requirements on speed of control rod response and thus improves plant safety. Every 2-3 months, the control rod patterns are altered to provide more uniform fuel and control rod burnup. In normal daily operation, little control rod movement is required for depletion of reactivity. The resulting low frequency of control rod changes reduces the possibility of operator error. 

Boron concentration in the in-containment refuelling water storage tank is maintained between 2600 ppm and 2900 ppm. This margin ensures long term reactivity control after a large-break LOCA event as described in Section 15.6.5.4C.4 of Reference 6.1. 

Give long term reactivity changes resulting directly from a reactor shut-... 

Are the net long term reactivity gains large at present fuel expos ure ranges ... 

Answer No - The net long term reactivity gains from these metal effects is... 

Using Fig ore 15, explain the net long term reactivity changes occurring in a column of green metal during a normal operating period. 

Specific power Boiling channels 19.7 kW/kg. Superheat channel 15.3 kW/kg Shutdown Boric acid solution in interlattice tubes, plus D2O dump. Control D2O height for power control. Boric acid concentration in moderator for long-term reactivity changes. Flooding groups of interlattice tubes for spectral shift flux control... 

Based on observation of long-term reactivity effects in the present Hanford reactors, the cold long term effect is positive in natural uranium fuel up to an exposure of 550 Ml /T. In... 

Fig. 4.4. Long-term reactivity variation in a natural uranium reactor. The curves labeled 1 and 2 are the reactivity contributions due to high cross-section fission products (excluding Xe ) and low cross-section fission products, respectively [from H. Rose and J. J. Syrett, J. Brit. Nucl. Energy Conf., 179 (July 1959). (Courtesy of the British Nuclear Energy Society.)]...

CAREM design is within the boundaries of current requirements in relevant areas. However, the use of borated water as a long-term reactivity control is eliminated, resulting in less waste. 

Long-term reactivity changes caused by fuel burn-up, start-up xenon, xenon over-... 

Long-term reactivity controls Cote makeup tanks... 

FeS may also be a useful alternative or addition to zero-valent iron metal for some in-situ reactive barrier applications 11, 14), particularly since FeS has been shown to be an order of magnitude more reactive per unit surface area than iron metal 12), and addition of pyrite and FeS to zero-valent iron has been shown to reduce the degradation time of CT 8). Factors affecting the long-term reactivity of iron sulfide minerals in field-scale remediation applications have yet to be explored, however. Generating FeS in-situ by enhancing the growth of... 

Chernobyl reactors, predominantly rely on control rod positioning for reactivity control (Kulikov, 1984). BWR reactors, like Fukushima, can alter the steam to water ratio inside the core to provide reactivity control (US Nuclear Regulatory Commission, n.d.b). PWR reactors, like TMl, use liquid poisons (boric acid) inside the coolant loop to provide long-term reactivity control (Knief, 2008). 

Bridel J-S, Azais T, Morcrette M, Tarascon J-M, Larcher D (2011) In sim observation and long-term reactivity of Si/C/CMC composites electrodes for Li-ion batteries. J Electrochem... 

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