Displacement Measurement Sensor for Use in Loss-of-Fluid-Test Reactor

Qualification tests conducted for a period of 700 hours of each of three displacement measuring (LVDT) sensors confirmed applicability of the design for use in Loss-of-Fluid-Test (LOFT) reactor. Operationally, the sensor satisfied all specified requirements for LOFT. Even for imposed temperature transients at rates up to 100°F/s, the indicated displacement remained within the allowed maximum error band of ±10% of reading. The 0.625-in OD by 5.5-in long sensor exhibited a linearly related signal output variation for displacement variations of up to 1-in range. Long term operation at temperatures of 100°F to 800°F caused no perceptible permanent change of operating characteristics. Furthermore, operation of the displacement sensor during severe and varied qualification testing justifies the following conclusions: * All qualification sensors yielded linear variations of signal output with displacement changes for a range of 1-in and exhibited a change of sensitivity of less than 5% over the temperature range of 100 to 800°F. * For imposed temperature transients, by use of either laboratory ovens or an autoclave, the maximum measurement error of ±2% of reading remained. less than the allowed value (±10% of reading) for inaccuracy of LOFT displacement sensors. * The sensor speed of response to rapid displacements of the core easily satisfied the specified 100 millisecond requirement for LOFT. * Vibrations expected to occur during a LOFT transient should incur only minimal spurious signal response, as vibration tests at reactor system frequencies caused no discernable signals superimposed on the quiescent value.