Engineering Services/Nuclear: Three Mile Island Unit 2 Reactor D&D
|
MPR assisted GPU in cleanup of the damaged TMI 2 plant, and also served on the TMI 2 oversight group of industry experts established by the Department of Energy. We learned a number of important lessons from this experience, including:
|
 View Full Image |
|
|
- Burial costs represent a large fraction of decommissioning costs. Efforts to minimize waste volume can have a significant impact on reducing costs, and should be carefully integrated throughout both planning and implementation.
- Detailed planning should be short term and easily changed. This approach allows extensive and constant monitoring of actual plant conditions, providing engineering solutions appropriate to the actual work conditions, and adjustment of the work schedules on a daily basis.
Specific activities performed by MPR at TMI-2 are as follows:
- MPR developed a method for visual inspection of the top of the damaged
TMI-2 reactor core, and led the team that performed the inspection.
This task included the following activities:
- Engineering analysis, including mock-ups that showed access could be achieved through openings in the internals.
- Procurement of the equipment required to perform this inspection (miniature TV cameras and associated handling equipment).
- Training of inspection personnel.
- The inspection showed the actual extent of core damage for the first time, and permitted the development of realistic, de-fueling plans. Subsequently, MPR developed the de-fueling tools and methods for breaking damaged fuel bundles apart and lifting them out of the core.
- The US NRC contracted MPR to develop a method to remove large metallurgical samples from the lower head of the reactor vessel, and to direct the removal operations. This effort included the following accomplishments:
- The samples included the vessel cladding and selected in-core instrument nozzles.
- MPR designed tooling and developed procedures to: (1) plug several in-core instrument nozzles (to prevent leakage of water when selected nozzles were removed); (2) cut out samples remotely using metal disintegration machining; and (3) retrieve the samples and place them in shipping containers. The tooling was designed to be operated by personnel standing 40 feet above the lower vessel head operating through about 35 feet of water.
- Thirty-one samples were retrieved in 30 days, significantly greater than the goal of eight samples set by the NRC. The task was accomplished with significantly less personnel exposure than projected.
- MPR developed shielding and designed equipment to handle the highly radioactive resins produced during cleanup of the contaminated auxiliary building water. This work included removable shield covers for the resin vessels, lift rigging, and attachment tooling. This equipment was built and used successfully in the removal of spent resin vessels from their process locations.
- MPR evaluated various methods for removing radioactive krypton gas from the containment building prior to worker entry. This included the purge method which was ultimately used as well as several alternate systems to store or concentrate the gas. MPR assisted GPU in obtaining NRC approval for this method, and in responding to various anti-nuclear organizations opposed to the purging. These included the Union of Concerned Scientists, as well as local groups.
|
Some of our D&D assignments have required extraordinary engineering effort as well as creative and unconventional approaches. The following pages provide insight to our experience in a few of the nuclear D&D projects: |
Contact
For further information on MPR's D&D
services with the Department of Energy,
or other engineering services, contact Bob Coward or
Larry Cundy.
|
|