Plans for Chinshan6 March 2019
Taiwan’s first commercial nuclear power plant helped the island get through the international oil crisis during the 1970s. Now, Chinshan is leading the way in decommissioning, as Chang-Lin Hsieh and Yu-Kai Huang explain.
THE TAIWAN POWER COMPANY’S CHINSHAN nuclear power plant is located in New Taipei City’s Shimen district. Its two units are type-4 boiling water reactors with Mark I containment and a rated power of 636MWe.
Commercial operation started on 10 December 1978 at Chinshan 1 and 15 July 1979 for Chinshan 2. The operating licences for the two reactors were valid for 40 years. The operating licence for unit 1 expired on 5 December 2018. The plant entered its decommissioning phase the next day.
During its operational lifetime, Chinshan 1 produced 162.5TWh of electricity, and Chinshan 2 produced 175TWh – a combined total of 338TWh.
According to Taiwan’s Nuclear Reactor Facilities Regulation Act, a decommissioning plan must be submitted by the licensee three years prior to the scheduled permanent end of a nuclear reactor’s operating life.
TPC submitted the Chinshan decommissioning plan to the Atomic Energy Council (AEC) in November 2015, and it was approved by the AEC on 28 June 2017. It awaits a permit, which will follow approval of the environmental impact assessment submitted to the Environmental Protection Administration in January 2016 for review.
The decommissioning itself will be completed within 25 years of obtaining a decommissioning permit from the regulator. Activities will include decontamination, dismantling, and storage work within the shortest possible time, while complying with statutory requirements aimed at reducing expenses, ensuring radioactive safety, reducing personnel dosage, and minimising radioactive waste.
The Chinshan site can be separated into two areas: Xiao Keng and Qianhua. The radiation laboratory, offices, and warehouses are located in the Xiao Keng area. The main nuclear reactor facilities are in the Qianhua area – including the shared reactor buildings, turbine buildings, switchyard, low-level radioactive waste (LLRW) warehouses, gas turbine buildings, oil tanks, substation and the parking area.
The decommissioning plan for the Chinshan can be divided into four major phases: the decommissioning transition phase (8 years), the dismantling phase (12 years), the final site status survey phase (3 years), and the site restoration phase (2 years). The process is expected to reach completion in 2043.
The strategy will be immediate dismantling. After the permanent shutdown of the reactor, the first task is to remove the spent nuclear fuel from the core and to transfer it, first to the spent fuel pool then, ultimately, to the dry storage facilities. Safe operation of the spent fuel pool must be maintained until all the spent fuel has been transferred to dry storage. To accurately gauge the range of the contamination and make a strategy for decontamination, evaluation and radiation measurement of the systems, structures and components are necessary. Once all of the internal and external components in the target buildings have been fully dismantled and the contaminated concrete has been completely decontaminated, building structures can be dismantled and the site can be released.
The main objective of the process is to completely dismantle radioactively contaminated systems, equipment, and components, so dismantling work should be regarded as the core of the entire decommissioning process. Most major radioactive tasks take place during this phase, so work and radiation safety will be especially important.
Using as low as reasonably achievable (ALARA) work principles, the dismantling process will begin with the turbine building. Once the spent nuclear fuel has been moved from the spent fuel pool to dry storage, equipment dismantling in the joint building may begin. This will involve dealing with the reactor vessels, reactor vessel internals, bio-shield, spent fuel rack, the major piping system, tank, and large components. Plans and the scope of work for the dismantling of equipment will be arranged principally by floor, and each floor will be separated into several areas.
The wastes will include the reactor vessels, reactor internals, neutron activated waste, biological shielding, structure materials (concrete), etc. The process will produce some secondary waste such as waste oil, filters, shielding material, personnel clothing, contaminated equipment, etc. All of this waste must be classified appropriately.
To manage the LLRW during the decommissioning period, nearby areas in various buildings will be used to improve the proximity of monitoring and processing. Pipelines, equipment and component interiors will be decontaminated before dismantling to remove radioactive materials and reduce worker exposure. After dismantling, pipelines, equipment, and components with surface contamination will be decontaminated so that these materials reach standards that allow them to be conditionally or unconditionally released.
Plans have been made to release wastes that meet clearance levels or release criteria. This waste will be moved outside the plant for recycling and reuse to achieve resource sustainability objectives.
Once the radioactive equipment has been removed, the scrubbing and cleaning of contaminated concrete building surfaces can begin. Any potentially contaminated structures located at the surface or to a depth of one meter beneath the surface will be dismantled. If site surveys carried out during decommissioning reveal that structures are not contaminated, structures more than one meter underground may be left in place.
The reinforced concrete blocks produced through the dismantling of building structures will be managed through a concrete removal facility to be established at the parking area to the north of the site. This area will be used for relevant detection, demolition, and extraction of the steel reinforcements. Non-contaminated concrete will be broken into small pieces and used as fill material for spaces more than one meter below the ground surface. After the buildings are dismantled, a final site status survey will be undertaken to and make sure the site’s radiation dosages meet the regulatory requirements for release. Once this is complete land remediation and restoration can be started.
As LLRW and high-level radioactive waste (HLRW) disposal sites have yet to be established in Taiwan, current plans call for the temporary storage of wastes in LLRW warehouses. There are two LLRW warehouses at Chinshan and a third is planned for an appropriate location. During the decommissioning period, waste gravel storage areas may be established according to the requirements of the constructed facilities. These will be used for storing non-radioactive rubble and waste gravel generated during the construction of new facilities. After decommissioning is complete, some area will not be released and will be converted to reservation areas for the temporary storage of radioactive wastes until final disposal sites are established. The waste will eventually be transported to the final disposal sites.
After decommissioning, the whole site, with the exception of the reserved areas, will be used by the power company. The Simulator Training Centre area will be repurposed as a small memorial park. All released areas will meet the rules specified in Clause 17 of the Enforcement Rules for the Implementation of Nuclear Regulation Act, specifically, the Annual Total Effective Dose Equivalent for general people cannot exceed 0.25mSv.
There are short, medium and long-term strategies for spent fuel management. The short-term strategy is to temporarily store material in the spent fuel pool. The medium-term strategy is to store material in dry storage facilities on site. The long-term strategy is to plan and develop a final disposal site in the future.
Construction of the Phase 1 dry storage facility at Chinshan was completed in 2013. It can house 56 assemblies in each of its 30 casks (1680 spent fuel assemblies). The unit cannot be decommissioned until all 816 fuels rods have been removed from the core. However, the New Taipei City municipal government has yet to issue a permit for the facility’s soil and water conservation plan. As a result, material currently stored in the pool cannot be transferred to dry storage and the storage pool has reached full capacity. In consequence, the spent fuel will be temporarily stored in the reactor core and additional costs are being paid to maintain the storage pool. These costs will continue to be incurred until the local government permits TPC to use the dry storage facility. In the interim, TPC will continue to follow the legal process. Once permission is granted, TPC will remove the fuel from the reactor core and begin decommissioning.
In order to ensure nuclear safety, the AEC requires that cooling, water clean-up and water supply systems continue to operate in accordance with rules until the spent fuel can be removed. The monitoring and maintenance of the systems is continuing and AEC will carry out inspections to ensure TPC is meeting operating standards. AEC has also requested that TPC modify the final safety analysis report (FSAR) and technical specification (TS) to the standard of scheduled outage by including extra regulatory requirements called “Mode 5 +.” These steps are intended to further enforce nuclear safety and prevent radiation leakages from the plant.
Four Phases of D&D
Phase 1. The decommissioning transition phase (2018-2026):
- Remove the spent nuclear fuel from the reactor core
- Preliminary site characterisation survey
- System decontamination (further evaluation needed)
- Decommissioning necessary system adjustment
- The construction of a Phase 2 dry storage facility
- The construction of a low-level radioactive waste warehouse
- Preparation, planning and procurement work
- Other evaluation and prioritised dismantling work
Phase 2. The dismantling phase (2026-2038):
- Transfer the spent nuclear fuel to the dry storage facility
- Dismantle the reactor vessel and internals
- Dismantle the contaminated system, equipment and components
- Surface decontamination of the contaminated concrete and structure
Phase 3. The final site status survey phase (2038-2041):
- Dismantle non-contaminated concrete and structures
- Conduct the final site status survey
Phase 4. The site restoration phase (2041-2043):
- Dismantle other buildings
- Land remediation
- Submit documents to regulators
Author information: Chang-Lin Hsieh, Nuclear engineer, Department of Nuclear Back-end Management, Taiwan Power Company; Yu-Kai Huang, Nuclear engineer, Department of Nuclear Back-end Management, Taiwan Power Company