Event Notification Report for March 23, 2011

EMERGENCY RETRACT MECHANISM FAILURE

The Varian equipment representative provided notification of the following event that occurred at the Grady Memorial Hospital in Atlanta, GA.

A technician was installing a Varisource IX high-dose afterloader when the active wire composed of a 10 Ci Ir-192 source failed to extend. After troubleshooting it was discovered that the wire was stuck on the wedge block which is part of the emergency retract mechanism. The active wire was removed and the emergency retract mechanism was replaced.

The technician received 0.2 mrem during the repair work.

PRESSURE TRANSMITTERS NEEDED FOR AUXILIARY FEEDWATER SUCTION PATH NOT ANALYZED FOR POTENTIAL HIGH ENERGY LINE BREAK

"While performing an extent of condition review of high energy line break (HELB) analyses, a detailed review of the auxiliary steam system was being performed. During this review, sections of pipe that run through rooms 1206/1207 in the Auxiliary Building were identified that have design ratings indicating that they could possibly be classified as high energy lines.

"The pipes were verified to have not been considered in the current HELB analyses. This condition affects pressure transmitters ALPT0037, 38, & 39 which are not qualified for operation in a harsh environment. These pressure transmitters provide the Auxiliary Feedwater Pump [AFW] Suction Transfer signal on low suction pressure from the non safety Condensate Storage Tank to the Safety Related supply (Essential Service Water).

"Technical Specification [TS] 3.3.2-6.h bases state: "since these detectors are in an area not affected by HELBs or high radiation, they will not experience any adverse environmental conditions and the Trip Setpoint reflects only steady state instrument uncertainties."

"Based upon the above bases, with the identified aux steam lines in service, the pressure transmitter's operability could not be assured. This represented an unanalyzed condition and had the potential to affect equipment used for accident mitigation. TS 3.0.3 was entered at time 2354 [CST] on 3/23/2011. At 0009 [CST] on 3/24/2011, Aux Steam valves FBV0158, FBV0I48, FAV0002, and FAV0003 were isolated, removing the HELB concern [TS 3.0.3 was exited at this time]. These are the active feed [isolation valves] to the lines passing through the Aux Building Rooms 1206/1207."

The licensee notified the NRC Resident Inspector.

* * * RETRACTION AT 1525 ON 5/19/2011 FROM DAVID BONVILLIAM TO MARK ABRAMOVITZ * * *

"On March 23, 2011, event notification EN 46693 documented that a harsh environment from a postulated High Energy Line Break (HELB) could affect pressure transmitter ALPT0037, 38 and 39. These pressure transmitters provide the Auxiliary Feedwater Pump suction transfer signal on low suction pressure from the Condensate Storage Tank to the safety-related water supply (Essential Service Water). This break was postulated to occur on auxiliary steam lines in Auxiliary Building rooms 1206 And 1207. This condition was initially reported both as an unanalyzed condition that significantly degraded plant safety and as a condition that could have prevented fulfillment of a safety function.

"When EN 46693 was reported, it was assumed that breaks were required to be postulated at any intermediate fitting, welded attachment, or valve on the subject auxiliary steam lines. Subsequent analysis shows that these sections of auxiliary steam piping are able to withstand safe shutdown earthquake (SSE) loadings and rupture loadings. For piping of this qualification, breaks at all intermediate fittings, welded attachments, and valves do not need to be postulated. Instead, line breaks are only required to be assumed at the terminal ends of the lines and at the locations specified for ASME Class 2 and 3 piping. None of these postulated break locations are located inside rooms 1206 and 1207.

"Analysis has been performed on these auxiliary steam lines for the remaining break locations that are required to be postulated. This analysis demonstrates reasonable assurance that safety related equipment, including pressure transmitters ALPT0037, 38 and 39, would have performed their safety functions following a postulated break of these auxiliary steam lines. Therefore, this condition does not meet the reporting requirements for an unanalyzed condition that significantly degraded plant safety or a condition that could have prevented fulfillment of a safety function.

"Event notification 46693 is hereby retracted.

"The NRC Resident Inspectors have been notified."

Notified the R4DO (Shannon).

POTENTIAL DEFECT IDENTIFIED IN A VARIAN MEDICAL SYSTEMS HIGH DOSE RATE AFTERLOADER

On March 23, 2011, a technician was installing a VariSource High Dose Rate (HDR) Afterloader - Model VariSource IX when the active wire composed of a 10 Ci Ir-192 source failed to extend. After troubleshooting it was discovered that the wire was stuck on the wedge block which is part of the emergency retract mechanism. (See NRC Event Notice 46695)

Engineering evaluation by the vendor, Varian Medical Systems, Inc., has identified a very small amount of material in the wedge block which has a small bore that the source wire passes through. Otherwise, nothing remarkable was identified.

This machine is a new unit with a very low number of source extensions. There is no history of similar events with new units of this type.

The vendor has issued a Tech Tip for all new sites and is investigating a new design for the wedge block with a goal of implementing any new design by April 30, 2012. Additionally, all VariSource HDR customers have received a copy of Customer Technical Bulletin CTB-VS-640A that discusses the potential of source wire path constriction and source wire jamming.