Trojan’s prompt approach to decommissioning1 February 1998
Faced by a premature shutdown of its Trojan nuclear plant, Portland General Electric (PGE) elected to manage the total decommissioning itself and to proceed with immediate decontamination and dismantlement as the most cost effective method.*
The Trojan plant, a 1178 MWe Westinghouse PWR, ceased operation on 27 January 1993 following some 18 years operation. The plant is located near the town of Rainier, Oregon.
The decision to close was taken following an extensive and public Least Cost Planning process which concluded that the potentially high costs of operating the plant and repairing or replacing the steam generators did not make economic sense.
PGE also decided that the best decommissioning path for Trojan was “prompt decommissioning” which involves the near-term decontamination, dismantlement and disposal of contaminated equipment.
Once this is completed, and the 10CFR50 licence is terminated by the Nuclear Regulatory Commission (NRC), the site buildings will remain standing and the fuel in dry storage. The subsequent demolishing of the buildings to a greenfield site will take place mid 2018 to late 2019, according to the current decommissioning plan.
Before much active decommissioning could take place, various transition activities had to be managed by PGE following shutdown. In order to achieve reductions in operating cost in a timely manner, PGE quickly developed and submitted a simplified Defueled Safety Analysis Report (DSAR) and simplified Technical Specifications to the NRC as well as a number of licence amendments and exemption requests. The NRC revised the Trojan operating licence to a Possession Only License on 5 May 1993. One year after plant closure, the key regulatory changes were in place allowing an 80% reduction in O&M costs.
The Trojan plant staff has been intimately involved in the development of the Trojan Decommissioning Plan which was approved by the NRC on 15 April 1996. Major decommissioning activities included the Large Component Removal Project, Reactor Vessel and Internals Removal Project, and construction of an Independent Spent Fuel Storage Installation.
Large component removal
Assessing the various options, PGE identified various cost and strategic advantages by performing the large component removal as soon as possible and managing the job itself. In particular, by completing the work by the end of 1995 several million dollars could be saved through negotiating favourable waste burial rates and by making efficient use of existing plant staff.
The option of managing the project itself rather than using a turnkey contractor was based on an estimated cost savings of $1.5 million, including higher contingencies because of the additional risk to PGE. The risk analysis revealed that, while some risks to PGE were reduced using a contractor, the final cost and political risks remained with the utility. In addition, PGE had retained people with experience managing similar projects at Trojan.
The Large Component Removal Project was completed on 1 November 1995. It entailed the removal, packaging, transportation, and disposal of the four steam generators and the pressuriser. They were transported via barge and overland transport to the US Ecology low-level waste facility at Hanford. There was a significant level of regulatory oversight in this project because of the following unusual situation:
• The project was performed prior to the decommissioning plan being approved by NRC.
• The existing regulations did not apply directly to the shipments.
• Water and land transport were involved.
By shipping these components as self contained, single transportation packages, PGE was able to realise substantial cost savings as well as reductions in personnel radiation exposure. The Trojan Decomm-issioning Project team functioned as the overall project manager for this activity. The project consisted of development of the project activities and schedule, obtaining necessary federal and state regulatory approvals, implementation and control of preparatory field work, oversight of contractors involved in the project, development and implementation of a Transportation Safety Plan, and responsibility for all activities related to transportation of the packages.
In order to allow shipment of these components as self-contained packages, PGE sought and obtained Certificates of Compliance for the packages from the NRC. Due to the high quality of the Safety Analysis Report very few questions were received from the NRC and the certificate was issued in approximately five months.
Despite the significant efforts of local anti-nuclear activists the project was completed on schedule and $1.6 million under budget.
Reactor vessel & internals removal
The Reactor Vessel and Internals Removal Project entails the removal, packaging, transport, and disposal of the reactor vessel and internals as one package. By shipping these as a single package, PGE will realise significant cost savings as well as reductions in personnel radiation exposure. As with the Large Component Removal, the Trojan Decommissioning Team is the overall project manager for this job. Activities completed to date include the development of the overall project plans and schedule, development of all work scope bid proposals and awarding the related contracts. PGE has also completed the package design and a safety analysis report and submitted a licence application for a Certificate of Compliance. Trojan field activities have commenced and will continue until the package is shipped.
Independent Spent Fuel Storage Installation
To facilitate decommissioning, PGE is constructing an Independent Spent Fuel Storage Installation (ISFSI) to contain and store not only spent fuel but also fuel debris and Greater Than Class C (GTCC) waste until a DOE or other offsite facility is available for permanent disposal. The Trojan ISFSI will be granted a site specific license as opposed to a general licence. PGE has completed the final release radiation surveys for the ISFSI site and is overseeing the design and licensing activities. The Trojan ISFSI will be the first facility to utilise Sierra Nuclear’s TranStor fuel storage & transport system. PGE submitted the ISFSI licence application to the NRC in March 1996.
PGE is also pursuing necessary testing and regulatory approval for the use of thermal treatment technology (steam reforming) for the reduction of organic material (filter media) currently stored in the Trojan spent fuel pool. The processing and encapsulation of the fuel debris currently entrained on the filter media is necessary to permit the long term storage of this material in the Trojan ISFSI and facilitate the decommissioning of the Trojan spent fuel pool.
In addition to these projects, PGE has completed the removal of such major components as the emergency diesel generators, reactor coolant pumps and motors, residual heat removal heat exchangers, charging pumps and motors, and a low-level radwaste storage building. In addition, it should be noted that the reactor coolant pumps will be shipped as I-2 SCO packages which were self-certified by PGE.
DECOMMISSIONING IN 1998
The decommissioning efforts for 1998 include a significant increase (by a factor of three over 1997) in work scope in the amount of decontamination and dismantlement work conducted in the containment and the reactor fuel building. The goal is to be substantially completed with equipment removal in 1998 and begin removal of embedded pipe and start surface decontamination of concrete.
Considerable time will be spent in support of regulatory reviews of the reactor vessel and internals removal project. The vessel will be shipped in 1999. Trojan expects to receive a Part 72 licence for the ISFSI and be ready to load fuel by he end of 1998.