Headquarters Daily Report MARCH 11, 1998 *************************************************************************** REPORT NEGATIVE NO INPUT ATTACHED INPUT RECEIVED RECEIVED HEADQUARTERS û REGION I û REGION II û REGION III û REGION IV û PRIORITY ATTENTION REQUIRED MORNING REPORT - HEADQUARTERS MARCH 11, 1998 Licensee/Facility: Notification: MR Number: H-98-0046 Proposed Generic Communication Date: 03/11/98 Subject: Disablement of Non-Power Reactor Scram System Discussion: The NRC intends to issue an Information Notice to non-power reactor licensees to alert them to two recent events at non-power reactors. In one case the entire automatic scram system was disabled by a sticking switch combined with an undocumented modification to the reactor console wiring. In the second case, the control console was modified such that if a switch stuck, parts of the automatic scram system would be disabled. These events are significant because they directly involve the reactor safety system. Contacts: Alexander Adams, NRR Vern Hodge, NRR (301) 415-1127 (301) 415-1861 Email: axa@nrc.gov Email cvh@nrc.gov _ REGION IV MORNING REPORT PAGE 2 MARCH 11, 1998 Licensee/Facility: Notification: Texas Utilities Electric Co. MR Number: 4-98-0010 Comanche Peak 2 Date: 03/11/98 Glen Rose,Texas Telecon from Resident Inspectors Dockets: 50-446 PWR/W-4-LP Subject: PLANT RESTART AFTER REACTOR TRIP Reportable Event Number: 33863 Discussion: On March 9, Comanche Peak Unit 2 was returned to service after completing repairs to the turbine plant cooling water head tank level switch. The reactor was critical at 1:19 p.m. (CST) and the main generator was syncronized to the grid at 4:48 p.m. On March 8, 1998, Unit 2 experienced a loss of turbine plant cooling water system with subsequent turbine and reactor trips from 100 percent power. At the time of the trip, turbine plant cooling water system feed and bleed for chemistry control was being performed. During the feed and bleed, the makeup valve for the head tank did not automatically open, causing the tank to reach a lo-lo level which resulted in the turbine plant cooling water pumps tripping on low suction pressure. This resulted in the turbine primary water system exceeding the high temperature limit, causing a turbine trip and a corresponding automatic reactor trip. The decreasing level in the head tank did not initiate a control room alarm prior to the lo-lo level setpoint due to a level switch failure. The level switch normally opens the makeup valve at the 63 percent level and causes an alarm at the 6 percent level. Additionally, plant operators did not observe a lowering of the tank level during their plant rounds. All safety systems functioned normally on the trip. Following the trip, the operators took action to manually stop the turbine-driven auxiliary feedwater pump; however, a lo-lo steam generator level signal was present in more than one steam generator, causing the pump to restart automatically. The licensee is reviewing the operation of the turbine-driven auxiliary feedwater pump. During power ascension, the licensee identified an air leak on the feedwater regulating valve for Steam Generator 1. The power ascension was stopped at 80% power while repairs to the feedwater regulating valve were completed. The plant reached 100% power at 1:54 p.m. on March 10. Regional Action: The resident inspectors responded to the site upon notification of the plant trip. Followup activities for post-trip review, plant startup, and premature stopping of the turbine-driven auxiliary feedwater pump are being reviewed by the resident inspectors. Contact: Ronald A. Kopriva (817)860-8104 A. T. Gody (254)897-1500 _