[en] Reliable cost estimates are essential for the planning of a decommissioning program for a nuclear facility. The preparation of such cost estimates is a complex task because there are a large number of components, equipment, and piping systems to be considered, many different levels of radioactive contamination and activation levels to be examined, corresponding waste volumes for disposal to be determined and multiple decommissioning scenarios to be evaluated. The DECOM computer program was initially developed in 1983 for use on an IBM main frame computer. In 1985, in order to provide more flexibility and ease of operation for the users of the DECOM computer program, the DECOM Code was converted so as to be usable on an IBM-PC type microcomputer. The DECOM program has been used in the past few years to do decommissioning estimates for both CANDU (Canada Deuterium Uranium) and PWR (Pressurized Water Reactor) type reactors. The estimates have been found to be within the range reported in the OECD (Organization for Economic Cooperation and Development) decommissioning cost surveys. In order to test the validity of the cost estimates prepared using DECOM, a sample of actual cost and manhour data from the Gentilly-1 Decommissioning operation have been processed through the DECOM code and it was observed that the total cost figures were accurate within a 20% range, though costs for individual activities some instances differed. The AECL DECOM computer program, based on the widely accepted unit cost factor approach, is a versatile tool for the applications in decommissioning studies

[en] The experience gained and the lessons learned in testing both soft and hard chemical solutions in the decontamination of the in-pile CART-TC loop, located in ESSOR reactor at the European Communities JRC of Ispra, Italy, are described. The main objective of the work was to extend laboratory tests to a real small-scale loop in order to get operating experience on chemical decontamination of significant nuclear reactor systems and to evaluate the real advantages and limits of this technique in decommissioning activities. The main investigations were conducted in order to obtain knowledge on: testing both commercial and experimental chemical solutions, operating problems in aggressive environment, waste reduction and management, and to make an evaluation of the extension of this technique to the power plant. The results are presented

[en] To support interim storage of vitrified high level waste at the West Valley Demonstration project, the shielded, remotely operated Chemical Process Cell (CPC) was decommissioned and decontaminated. All equipment was removed, packaged and stored for future size reduction and decontamination. Floor debris was sampled, characterized, and vacuumed into remotely handled containers. The cell walls, ceiling, and floor were decontaminated. Three 20 Mg (22.5) ton concrete neutron absorber cores were cut with a high pressure water/abrasive jet cutting system and packaged for disposal. All operations were performed remotely using two overhead bridge cranes which included two 1.8 Mg (2-ton) hoists, one 14.5 Mg (16-ton) hoist, and an electro-mechanical manipulator. Additional operations were performed by an industrial robot mounted on a mobile platform. Initial general area dose rates in the cell ranged from 1 to 50 R/hr and were reduced significantly. Target levels of less than 10 mR/hr general area readings were established before decontamination and decommissioning was initiated. The specific results obtained are summarized

[en] Each of plutonium production reactors at Hanford had a large water-filled spent fuel pool to provide interim storage of irradiated fuel while awaiting shipment to the separation facilities. After cessation of reactor operations the fuel was removed from the pools and the water levels were drawn down to a 5- to 10-foot depth. The pools were maintained with the water to provide shielding and radiological control. What appeared to be a straight forward project to process the water, remove the sediments from the basin, and stabilize the contamination on the floors and walls became a very complex and time consuming operation. The sediment characteristics varied from pool to pool, the ion exchange system required modification, areas of hard-pack sediments were discovered on the floors, special arrangements to handle and package high dose rate items for shipment were required, and contract problems ensued with the subcontractor. The original schedule to complete the project from preliminary engineering to final stabilization of the pools was 15 months. The actual time required was about 25 months. The original cost estimate to perform the work was 2,651,000. The actual cost of the project was $5,120,000, which included $150,000 for payment of claims to the subcontractor. The experiences associated with the cleanup and radiological stabilization of the 100-B, -C, -D, and -DR spent fuel pools, and discusses a number of lessons learned items are summarized

[en] The techniques up to this time for removing contaminated concrete surfaces have some problems, such as irregular depth of removal, difficulty of collecting the scraped debris and so on. As a solution of these problems, a new method with original milling cutter and vacuum collecting system had been developed. The milling cutter can scrape the concrete surface to a few millimeters depth accurately by one pass. The scraped debris is shaped uniform powder and is collected almost 100% by a vacuum collecting system. This method has many advantages, such as radioactive waste reduction, prevention from internal exposure of workers, recontamination prevention and easy measurement of residual radioactivity after decontamination. The development, demonstration, experience and outline of the new method completed as Clean Cut Removal System are discussed

[en] During the Surry Steam Generator Repair Program it was necessary to cut the steam generator into two (2) pieces and to remove sections of the reactor coolant piping, feedwater piping, main steam piping, and instrumentation lines. Many of the cutting techniques and measures taken to minimize personnel exposure are directly applicable for use in nuclear power station decommissioning. These techniques are discussed as they were used at Surry

[en] Two Hanford Site contractors independently formulated readiness review methods to prepare for decontamination and decommissioning (D and D) projects. One readiness review method provided an independent management review process. The other method provided a review by personnel directly involved in the project and concise documentation procedures. A unified system is now used at Hanford which combines the best aspects of both readiness review methods. The unified method assigns category levels based on certain job characteristics. The category assigned to the project then indicates the required level of management review prior to proceeding with the D and D project. In addition, the concise documentation procedures are now used for all category levels

[en] Two tools have been developed for use by the nuclear industry: the Deep Kerf tool and the Cleaner/Scarifier tool. The Deep Kerf tool is designed to cut through thick, reinforced concrete structures to facilitate their decommissioning. It employs the abrasive-waterjet (AWJ) cutting technology. The basis of the system is a rotary nozzle that makes a slot in the concrete wide enough to accommodate the cutting tool as it advances. In this program, concrete as thick as 1.5 m was cut through from one side. A shroud and vacuum system covers the opening of the slot during cutting to contain the spoils with greater than 99% efficiency. The Cleaner/Scarifier tool was designed for removing the surface layers of contaminated concrete and decontaminating metal surfaces. It uses ultrahigh-pressure waterjets mounted on a rotating arm to remove or clean the target surface. Spoils recovery with a shroud and vacuum system is over 99% complete for both horizontal and vertical surfaces

[en] The CANDU reactor was designed so that any or all of the components which make up the reactor channels can be removed and replaced. It has always been expected that at least once during the lifetime of a CANDU nuclear power station, the reactor channels would require replacement, and that this feature of being able to replace the reactor channels may allow extension of the life of a CANDU nuclear station far beyond the normal amortization life. The components of the reactor channel are shown. The process of replacing the fuel channels is discussed

[en] From the view of radiation control, the main features of the JPDR reactor dismantling are: 1. the work under high-level radiation and high level radioactive air contamination area is expected; the new dismantling techniques which have not been experienced in the controlled area before will be adopted; and a great amount of materials, tools, radioactive waste and so on will be taken out from the controlled area. Considering these features, five instruments were developed to adapt for the JPDR decommissioning; i.e., remote high dose rate measuring instruments (underwater and in the air), contamination inspection monitor, respirable dust monitor, respirable dust monitor, extremely low level waste γ-scanner, and waste package contamination and dose rate monitor. These instruments are described