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On January 9, 2002, at 1416 hours, with th … On January 9, 2002, at 1416 hours, with the reactor at 100% power, Quad Cities Nuclear Power Station Unit 1 jet pump #20 hold-down beam failed, causing a trip of the "B" recirculation pump motor and a high main steamline (MSL) radiation alarm. Per Technical Specifications, the reactor was taken to Mode 3 (shutdown).</br></br>The preliminary root cause of the failure of the jet pump #20 hold-down beam was intergranular stress corrosion cracking in the transition portion of the beam. The "B" recirculation pump motor tripped due to the introduction into the recirculation pump impeller of a piece of the failed beam. The MSL high radiation alarm was due to the changes in flow dynamics and mixing in the annulus region of the vessel due to the jet pump failure, which caused increased carryover of Nitrogen-16 into the MSLs.</br></br>The safety significance of this event was minimal. All emergency core cooling systems were operable during this event. The failure of the jet pump was readily detected from diverse plant parameters displayed in the control room, and the reactor was shut down within eight hours of initial indications.</br></br>Corrective actions included replacing all of the original-style BWR/3 jet pump hold-down beams with BWR/4 beams on Units 1 and 2, replacing the "B" recirculation pump impeller and repairing jet pump #20. pump impeller and repairing jet pump #20. +
On January 9, 2002, at 1416 hours, with th … On January 9, 2002, at 1416 hours, with the reactor at 100% power, Quad Cities Nuclear Power Station Unit 1 jet pump #20 hold-down beam failed, causing a trip of the "B" recirculation pump motor and a high main steamline (MSL) radiation alarm. Per Technical Specifications, the reactor was taken to Mode 3 (shutdown).</br></br>The preliminary root cause of the failure of the jet pump #20 hold-down beam was intergranular stress corrosion cracking in the transition portion of the beam. The "B" recirculation pump motor tripped due to the introduction into the recirculation pump impeller of a piece of the failed beam. The MSL high radiation alarm was due to the changes in flow dynamics and mixing in the annulus region of the vessel due to the jet pump failure, which caused increased carryover of Nitrogen-16 into the MSLs.</br></br>The safety significance of this event was minimal. All emergency core cooling systems were operable during this event. The failure of the jet pump was readily detected from diverse plant parameters displayed in the control room, and the reactor was shut down within eight hours of initial indications.</br></br>Corrective actions included replacing all of the original-style BWR/3 jet pump hold-down beams with BWR/4 beams on Units 1 and 2, replacing the "B" recirculation pump impeller and repairing jet pump #20. pump impeller and repairing jet pump #20. +
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1 +
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15:11:52, 27 November 2017 +
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