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iLAMP: Neutron Absorber Material Monitoring for Spent Fuel Pools
The spent fuel pool at TVA’s Watts Bar nuclear power plant near Spring City, Tenn. (Photo: TVA)
Neutron absorber materials are used by nuclear power plants to maintain criticality safety margins in their spent nuclear fuel pools. These materials are typically in the form of fixed panels of a neutron-absorbing composite material that is placed within the fuel pools. (A comprehensive review of such materials used in wet storage pools and dry storage has been provided by the Electric Power Research Institute (EPRI) [1]).
With increasing plant life, there is a need to maintain or establish a monitoring program for neutron absorber materials—if one is not already in place—as part of aging management plans for reactor spent fuel pools.
Such monitoring programs are necessary to verify that the neutron absorbers continue to provide the criticality safety margins relied upon in the criticality analyses of a reactor’s spent fuel pool. To do this, the monitoring program must be capable of identifying any changes to the material and quantifying those changes. It should be noted that not all the changes (for example minor pitting and blistering of the absorber material) will result in statistically or operationally significant impact on the criticality safety margins.
For monitoring neutron absorber materials in spent fuel pools, until recently, two alternatives existed—coupon testing and in situ measurements. A third option, called industry-wide learning aging management program (i-LAMP), was proposed by EPRI and is currently in the final stages of the regulatory review. The following sections describe these monitoring approaches.
Jiyun Zhao, Pradip Saha, Mujid S. Kazimi
Nuclear Technology | Volume 164 | Number 1 | October 2008 | Pages 20-33
Technical Paper | Icapp '06 | doi.org/10.13182/NT08-A4005
Articles are hosted by Taylor and Francis Online.
As the last topic of a series of U.S. reference supercritical water-cooled reactor (SCWR) design stability studies, coupled neutronic-thermal-hydraulic out-of-phase stability is analyzed and compared with that of a typical boiling water reactor (BWR). A modal expansion method based on modes (reactivity modes) of the neutron kinetic equation is applied, and the first subcritical mode of the neutron dynamics model is coupled with the coolant thermal-hydraulic model. The out-of-phase oscillation of the SCWR is found to be dominated by the reactor thermal hydraulics, whereas the BWR is more sensitive to the coolant density reactivity coefficient because of much stronger neutronic coupling. It is also found that the SCWR stability is sensitive to the details of the core simulation model and the hottest channel dominates the stability. The BWR is less sensitive to the core simulation model since it has much stronger neutronic coupling that is controlled by the whole-core average properties. Power and flow rate sensitivity analysis of the out-of-phase stability was also conducted for both the SCWR and the BWR. The SCWR stability is found to be more sensitive to the operating parameters than the typical BWR. Although the water rod heating can improve the SCWR out-of-phase stability, it cannot significantly improve the sensitivity feature.