ML101170787
| ML101170787 | |
| Person / Time | |
|---|---|
| Site: | Crystal River  |
| Issue date: | 11/23/2009 |
| From: | Robert Carrion NRC/RGN-II |
| To: | Lake L NRC/RGN-II |
| References | |
| FOIA/PA-2010-0116 | |
| Download: ML101170787 (3) | |
Text
Carrion, Robert From:
Sent:
To:
Subject:
Attachments:
Carrion, Robert Monday, November 23, 2009 9:09 AM Lake, Louis Charter Item #1 Description - Charter Item #1 (Rev 22Nov09).doc
- Lou, Take a look at the attached for Item #1. Let me know if you need/want more detail and/or information.
Bob
Charter Item #1.
Develop a complete description of the problems and circumstances surrounding the gap in the containment building.
The Crystal River Unit 3 containment is a steel-lined, post-tensioned concrete structure nominally 42 inches thick. Post-tensioning is achieved utilizing an outer array of horizontal tendons immediately adjacent to an inner array of vertical tendons.
The licensee began Refueling Outage 16 on September 25, 2009 with a'ieduction in power from Mode 1. The unit continued down in power through Modes 2, 3, 4, and 5 on September 26. A major planned activity scheduled for this outage was the replacement of the steam generators. In preparation for the steam generator replacement, the licensee planned to make a construction opening approximately forty feet directly above the equipment hatch through which to remove the existing steam generators and transport the replacement steam generators into the Reactor Building. Upon reaching Mode 5 at approximately 17:00 hours on September 26, tendon work activities were begun. Two vertical tendons (34V12 and 34V13) were de-tensioned simultaneously. From September 26 through October 1, 8 additional vertical tendons and 16 hoop tendons were de-tensioned by plasma cutting as part of the process to make the required construction opening. The licensee began the hydrolazing/hydro-demolition of the containment/Reactor Building on September 30, 2009, as the first step in making the construction opening. This process was accomplished by using water under pressure (as great as 25000 pounds per square inch (psi) to "cut" the concrete. On October 3, during the hydro-demolition work to expose the first layer of tendon sheaths in the creation of the construction opening, water from the work was observed leaking from the exterior surface of the containment at various locations below the elevation of the bottom of the construction opening. The leaking water was not limited to the construction opening, but was observed at the edges of the construction opening extending into undisturbed concrete for an indeterminate distance but at least as far as the post-tensioning buttresses (Buttresses #3 and #4). As the hydrolazing/hydro-demolition work continued, some of the concrete rubble unexpectedly broke off into large pieces. Inspection of the construction opening by the licensee discovered a concrete cracking/delamination condition. It was located approximately in the cylindrical plane of the centerline of the hoop tendons, approximately nine to twelve inches from the exterior surface of the Reactor Building. Approximately 30 inches of unaffected concrete remained from the delaminated condition to the inside radius of the building, including the steel liner plate. To keep the focus on the project and outage execution, the licensee management team chose to obtain industry assistance from Sargent and Lundy and MPR Associates to develop contingency and mitigation strategies for managing project risk.
The hydro-demolition of the concrete continued through October 7, when the Reactor Building liner was exposed and all concrete had been removed down to the liner.
Upon realizing that this was indeed an unusual and unexpected condition, the licensee assembled a technical analysis group dedicated to: 1) the determination of the extent of condition, 2) the determination of the root cause; 3) the design basis analysis, and 4) the repair alternatives analysis. Each area was enhanced by support from external entities. Constru~tion Technology
Laboratories (CTL), a contractor with expertise in non-destructive testing of large concrete structures, was commissioned to determine the extent of the delamination, with verification by core bores and boroscope visual techniques. Another team, Performance Improvement International (PII), recognized for its root cause analyses in these sorts of structural failures, was commissioned to determine the root cause for this event. The licensee also commissioned MPR Associates, Inc. and established teams to review the effect of the delamination on the design bases and design margin of the containment structure. Structural Preservation Systems was commissioned to analyze repair alternatives. Numerous subcontractors also support these activities This effort was placed under the responsibility of the Containment Project Manager.
The Containment Project Manager was also responsible for interfaces with INPO, NEI, the NRC, media, etc. as well as project controls dealing with scheduling, contract administration, and financial issues.