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The accident at the Three Mile Island Unit 2 (TMI-2) reactor provided a unique opportunity to evaluate sensors exposed to severe accident conditions. The loss of coolant and the hydrogen combustion that occurred during this accident exposed instrumentation to harsh conditions, including direct radiation, radioactive contamination, and high humidity with elevated temperatures and pressures. As part of a program initiated by the Department of Energy Office of Nuclear Energy (DOE-NE), a review was completed to gain insights from prior TMI-2 sensor survivability and data qualification efforts. This new effort focused upon a set of sensors that provided critical data to TMI-2 operators for assessing the condition of the plant and the effects of mitigating actions taken by these operators. In addition, the effort considered sensors providing data required for subsequent accident simulations. Over 100 references related to instrumentation performance and post-accident evaluations of TMI-2 sensors and measurements were reviewed. Insights gained from this review are summarized within this paper. As noted within this paper, several techniques were invoked in the TMI-2 post-accident program to evaluate sensor survivability status and data qualification, including comparisons with data from other sensors, analytical calculations, laboratory testing, and comparisons with sensors subjected to similar conditions in large-scale integral tests and with sensors that were similar in design but more easily removed from the TMI-2 plant for evaluations. Conclusions from this review provide important insights related to sensor survivability and enhancement options for improving sensor performance. In addition, this paper provides recommendations related to sensor survivability and the data evaluation process that could be implemented in upcoming Fukushima Daiichi recovery efforts. [ABSTRACT FROM PUBLISHER]

An instrumented creep testing capability is being developed for specimens irradiated in pressurized water reactor coolant conditions at the Advanced Test Reactor (ATR). A test rig has been developed such that samples will be subjected to stresses up to 350 MPa at temperatures up to 370°C in pile. Initial Idaho National Laboratory (INL) efforts to develop this creep testing capability for the ATR are summarized. In addition to providing an overview of in-pile creep test capabilities available at other test reactors, this paper reports efforts by the INL to evaluate a prototype test rig in an autoclave at INL's High Temperature Test Laboratory. Data from autoclave tests with Type 304 stainless steel and copper specimens are reported. [ABSTRACT FROM AUTHOR]

Many of the sensors deployed at materials and test reactors cannot withstand the high flux/high temperature test conditions often requested by users at U.S. test reactors, such as the Advanced Test Reactor (ATR) at the Idaho National Laboratory. To address this issue, an instrumentation development effort was initiated as part of the ATR National Scientific User Facility in 2007 to support the development and deployment of enhanced in-pile sensors. This paper provides an update on this effort. Specifically, this paper identifies the types of sensors currently available to support in-pile irradiations and those sensors currently available to ATR users. Accomplishments from new sensor technology deployment efforts are highlighted by describing new temperature and thermal conductivity sensors now available to ATR users. Efforts to deploy enhanced in-pile sensors for detecting elongation and real-time flux detectors are also reported, and recently-initiated research to evaluate the viability of advanced technologies to provide enhanced accuracy for measuring key parameters during irradiation testing are noted. [ABSTRACT FROM AUTHOR]

Over 50 years of nuclear fuels and materials irradiation testing has led to many countries developing significant improvements in instrumentation to monitor physical parameters and to control the test conditions in material test reactors (MTRs). Recently, there is increased interest to irradiate new materials and reactor fuels for advanced pressurized water reactors and Gen-IV reactor systems, such as sodium-cooled fast reactors, very high temperature reactors, supercritical water-cooled reactors, and gas-cooled fast reactors. This review paper documents the current state of instrumentation technologies in MTRs in the world and summarizes ongoing research efforts to deploy new sensors. As described in this paper, a wide range of sensors is available to measure key parameters of interest during fuels and materials irradiations in MTRs. Ongoing development efforts focus on providing MTR users a wider range of parameter measurements with smaller, higher accuracy sensors. [ABSTRACT FROM AUTHOR]

A key component of the Advanced Test Reactor (ATR) National Scientific User Facility (NSUF) effort is to expand instrumentation available to users conducting irradiation tests in this unique facility. In particular, development of sensors capable of providing real-time measurements of key irradiation parameters is emphasized because of their potential to increase data fidelity and reduce posttest examination costs. This paper describes the strategy for identifying new instrumentation needed for ATR irradiations and the program underway to develop and evaluate new sensors to address these needs. Accomplishments from this program are illustrated by describing new sensors now available to users of the ATR NSUF. In addition, progress is reported on current research efforts to provide improved in-pile instrumentation to users. [ABSTRACT FROM AUTHOR]

A key component of the Advanced Test Reactor (ATR) National Scientific User Facility (NSUF) effort is to develop and evaluate in-pile instrumentation capable of providing real-time measurements of key parameters during irradiation. This paper describes the strategy for prioritizing instrumentation needs and the program to develop new or enhanced sensors to address these needs. Accomplishments from this program are illustrated by describing new sensors now available to users of the ATR NSUF with data from irradiation tests using these sensors. In addition, progress is reported on research efforts to provide users advanced methods for detecting temperature, fuel thermal conductivity, and changes in sample geometry. [ABSTRACT FROM PUBLISHER]

As part of a process initiated through the Advanced Test Reactor (ATR) National Scientific User Facility (NSUF) program to make Silicon Carbide (SiC) temperature monitors available for experiments, a capability was developed at the Idaho National Laboratory (INL) to complete post-irradiation evaluations of these monitors. INL selected the resistance measurement approach for detecting peak irradiation temperature from SiC temperature monitors. To demonstrate this new capability, comparison measurements were completed by INL and Oak Ridge National Laboratory (ORNL) on identical samples subjected to identical irradiation conditions. Results reported in this paper indicate that the resistance measurement approach yields similar peak irradiation temperatures if appropriate equipment is used and appropriate procedures are followed. [ABSTRACT FROM AUTHOR]

Several options have been identified that could further enhance the reliability and extend the applicability ofhigh-temperatureirradiation-resistantthermocouples (HTIR-TCs) developed by the Idaho National Laboratory (INL) for in-pile testing, allowing their use in temperature applications as high as 1800%C.The INL and the University of Idaho (UI) investigated these options with the ultimate objective of providing recommendations for alternate thermocouple designs that are optimized for various applications. This paper reports results from INL/UI investigations. Results are reported from tests completed to evaluate the ductility, resolution, transient response, and stability of thermocouples made from specially formulated alloys of molybdenum and niobium,not considered in initial HTIR-TC development. In addition, this paper reports insights gained by comparing the performance of HTIR-TCs fabricated with various heat Ntreatments and alternate geometries.ABSTRACT FROM PUBLISHERCopyright of Nuclear Technology is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. [ABSTRACT FROM AUTHOR]

This paper addresses the pool boiling critical heat flux (CHF) phenomena in one-dimensional inclined rectangular channels by changing the orientation of a copper test heater assembly. In a pool of saturated water at atmospheric pressure, an account is taken of the gap sizes of 1, 2, 5, and 10 mm and the surface orientation angles from the downward-facing position (180 deg) to the vertical position (90 deg). Tests art, conducted on the basis of the visualization of boiling phenomena utilizing a high-speed digital camera. In addition, an engineering correlation relating to the CHF near the vertical position is developed anchored in the experimental results. It is observed that the CHF generally decreases as the surface inclination angle increases and as the gap size decreases. In the downward-facing position (180 deg), on the other hand, the vapor escape and liquid refill are accelerated by the squeezing gap so that the CHF tends to increase as the gap size decreases. It is also found that there exists a transition angle, around which the CHF changes with a rapid slope on account of the CHF triggering mechanism differing with the inclination angle. [ABSTRACT FROM AUTHOR]