Evaluation of thermal devices for detecting in-vessel coolant levels in PWRs

Technical Report · Sun Aug 01 00:00:00 EDT 1982

OSTI ID:6869660

Hardy, J E; Davis, C E; Turnage, K G; Anderson, R L

From investigations conducted immediately after the Three Mile Island nuclear power plant accident, some safety areas needing improvement were identified. One new US NRC requirement was the unambiguous detection of the approach to adequate core cooling. Designs to meet this requirement have generally included new instrumentation to monitor the coolant level in the reactor vessel. Thermal sensors proposed for use in pressurized-water reactor (PWR) vessels were tested and evaluated. The thermal devices tested use pairs of K-type thermocouples or resistance temperature detectors to sense the cooling capacity of the medium surrounding the device. One sensor of the pair is heated by an electric current, while the unheated one senses the ambient fluid temperature. The temperature difference between the heated and unheated sensors provides an indication of the cooling capacity of the surrounding fluid. Experiments that simulated the thermal-hydraulic conditions of a postulated PWR loss-of-coolant accident (LOCA) were run, including both natural- and forced-convection two-phase flow tests. Results suggest that thermal level devices generally indicate the existence of poor cooling conditions in LOCA environments. In some cases, however, the indication of the thermal devices may not be a direct measurement of water level. Shielding and separator tubes have been devised to ensure that the thermal sensors indicate the collapsed liquid level inside the separator tube. Preliminary evaluation of these protection systems is given.

• Research Organization: Oak Ridge National Lab., TN (USA)
• DOE Contract Number: W-7405-ENG-26
• OSTI ID: 6869660
• Report Number(s): NUREG/CR-2673; ORNL/TM-8306; ON: DE82021574; TRN: 82-022404
• Country of Publication: United States
• Language: English

Related Subjects

22 GENERAL STUDIES OF NUCLEAR REACTORS
21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
LOSS OF COOLANT
DETECTION
PWR TYPE REACTORS
REACTOR COOLING SYSTEMS
LEVEL INDICATORS
FORCED CONVECTION
NATURAL CONVECTION
SIMULATION
TEST FACILITIES
THERMOCOUPLES
THERMOMETERS
ACCIDENTS
CONVECTION
COOLING SYSTEMS
ENERGY SYSTEMS
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WATER COOLED REACTORS
WATER MODERATED REACTORS
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Light-Water Moderated
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