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On July 5, 2001, at 1006 hours, a manual S … On July 5, 2001, at 1006 hours, a manual Scram was initiated on Dresden Nuclear Power Station (DNPS) Unit 3 due to increasing drywell pressure. Drywell pressure increased because of rising containment temperature due to a disc to stem separation of the Reactor Building Closed Cooling Water (RBCCW) Temperature Control Valve (TCV) that supplies cooling water to the RBCCW heat exchangers. O One of the RBCCW loads is the drywell coolers. After the manual scram was initiated, drywell pressure continued to increase to a value above the Emergency Core Cooling System (ECCS) initiation setpoint. ECCS systems automatically initiated at 1.7 psig drywell pressure. The High Pressure Coolant Injection (HPCI) was placed in pull-to-lock to prevent a cold water injection. A Group 2 and Group 3 isolation also occurred during this event and all isolation valves successfully closed or isolated. All ECCS initiated and performed as designed.</br></br>A General Station Emergency Plan (GSEP) Alert was conservatively declared based on the assumption that the drywell pressure increased due to Reactor Coolant System (RCS) leakage. Subsequently, containment sampling and sump data determined that drywell atmospheric activity levels had remained normal, and no abnormal sump inputs had occurred (no indication of RCS leakage). The GSEP Alert was terminated on July 5, 2001 at 1602 hours.</br></br>The root cause of this event was the inappropriate torqueing of the valve stem into the valve disc by the manufacturer of the plug assembly. The cause of the manufacturer's failure to properly assemble the valve is unknown. The contributing causes of this event are poor communication of a similar previous event at Quad Cities, improper pin material being supplied by the vendor and Dresden's dependency on a single RBCCW train.</br></br>The safety significance of this event has been determined to be minimal.s event has been determined to be minimal. +
July 5, 2001 +
On July 5, 2001, at 1006 hours, a manual S … On July 5, 2001, at 1006 hours, a manual Scram was initiated on Dresden Nuclear Power Station (DNPS) Unit 3 due to increasing drywell pressure. Drywell pressure increased because of rising containment temperature due to a disc to stem separation of the Reactor Building Closed Cooling Water (RBCCW) Temperature Control Valve (TCV) that supplies cooling water to the RBCCW heat exchangers. O One of the RBCCW loads is the drywell coolers. After the manual scram was initiated, drywell pressure continued to increase to a value above the Emergency Core Cooling System (ECCS) initiation setpoint. ECCS systems automatically initiated at 1.7 psig drywell pressure. The High Pressure Coolant Injection (HPCI) was placed in pull-to-lock to prevent a cold water injection. A Group 2 and Group 3 isolation also occurred during this event and all isolation valves successfully closed or isolated. All ECCS initiated and performed as designed.</br></br>A General Station Emergency Plan (GSEP) Alert was conservatively declared based on the assumption that the drywell pressure increased due to Reactor Coolant System (RCS) leakage. Subsequently, containment sampling and sump data determined that drywell atmospheric activity levels had remained normal, and no abnormal sump inputs had occurred (no indication of RCS leakage). The GSEP Alert was terminated on July 5, 2001 at 1602 hours.</br></br>The root cause of this event was the inappropriate torqueing of the valve stem into the valve disc by the manufacturer of the plug assembly. The cause of the manufacturer's failure to properly assemble the valve is unknown. The contributing causes of this event are poor communication of a similar previous event at Quad Cities, improper pin material being supplied by the vendor and Dresden's dependency on a single RBCCW train.</br></br>The safety significance of this event has been determined to be minimal.s event has been determined to be minimal. +
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3 +
Modification date"Modification date" is a predefined property that corresponds to the date of the last modification of a subject and is provided by <a rel="nofollow" class="external text" href="https://www.semantic-mediawiki.org/wiki/Help:Special_properties">Semantic MediaWiki</a>.
15:12:19, 27 November 2017 +
September 4, 2001 +
July 5, 2001 +
URL"URL" is a <a href="/Special:Types/URL" title="Special:Types/URL">type</a> and predefined property provided by <a rel="nofollow" class="external text" href="https://www.semantic-mediawiki.org/wiki/Help:Special_properties">Semantic MediaWiki</a> to represent URI/URL values.