Extended hours: upgrading nuclear reactors

Plant-life extension (PLEX) and plant-life management (PLIM) are vital projects for ensuring the extended operational life of nuclear power plants (NPPs).

PLEX is a process that extends the original design life of the NPP through maintenance, engineering updates, technical improvements, safety upgrades, and modifications and refurbishment to equipment, after assessing the plant's technical, environmental and safety aspects to assure long-term operation.

PLIM supports PLEX by managing the plant in a safe and economic way to optimise its operating life and maximise its value. In PLIM, the plant undergoes continuous modifications and equipment replacement to improve operation and safety, which extends its economic life.

Most countries with nuclear power are extending the life of their NPPs to avoid investment in new installations because the capital cost for building new nuclear plants is considerably higher. Similarly, the capital cost of PLIM for long-term operation is lower compared with investing in replacement capacity. The majority of the capital costs are associated with the construction stage of the nuclear reactor and for ensuring safety standards. A typical nuclear electricity-generation cost breakdown is approximately 60% for capital investment, with operational, maintenance and fuel cycle costs accounting for about 20% each. Hence, life extension can potentially avoid huge capital costs.

PLEX also minimises the environmental costs associated with the equipment manufacturing that is required for the construction of NPPs, and avoids the primary energy costs needed for material procurement through plant commissioning. There are also decommissioning costs, which involve plant dismantling and site remediation, to consider. With extended plant life, this is spread over longer periods, thus reducing the cost per unit of power generated.

A further benefit is the enabling of continued power supply to the regional grid network, but the relative environmental and economic impacts of PLEX vis-à-vis other replacement options for power generation, such as wind power, is a crucial consideration and often depends on political decisions.

Generally, the design lifespan of a reactor is around 40 years. However, many plants have the engineering and technical capability to run beyond this, possibly up to 60-70 years. After about ten years of operation nuclear reactors begin to deteriorate mainly due to irradiation, thermal and mechanical loads, and corrosive and abrasive processes. This deterioration or ageing is the major factor in deciding the limit of PLEX. PLIM, meanwhile, helps to ensure that the plant continues to operate under optimum safety and performance parameters through repairs, and slows the ageing process.

The growing global demand for power is one of the main drivers behind the increasing importance of PLEX. During 2000-2010 electricity consumption grew at a compound annual growth rate (CAGR) of 3.5% from 13,044,433GWh to 18,454,883GWh. Consumption for 2012 to 2020 is expected to grow at a CAGR of 4%, rising from 20,114,049GWh to 27,496,560GWh.

Worldwide markets

The estimated global PLEX market for the period 2012-2020 is $64.7bn. North America is the largest market. Valued at $42.7bn, the US's share is $33.7bn with Canada contributing $9bn. The Nuclear Regulatory Commission (NRC) in the US has approved license renewals for around 71 reactors, with 15 currently under review and a further 17 more licence applications expected in the forecast period.

In Europe, the major PLEX markets are France, the UK, Russia and Ukraine with market values of $10bn, $1.9bn, $1.8bn and $1.7bn respectively. Numerous extensions were planned in Europe, but after the Fukushima disaster in March 2011 some countries are now phasing nuclear power out of their energy mix.

In the Asia-Pacific region, maximum extensions will take place in South Korea, which has a market value of $3.7bn. Japan had planned for extensions, but following the Fukushima disaster those plans are on hold.

Increasing the output capacity of a reactor is termed a power uprate. Globally, power uprates have been undertaken in the Asia-Pacific, European and North American regions. GlobalData's research shows the greatest number of uprates in the US followed by Sweden. The US saw an addition of approximately 295MW of capacity due to power uprates in 2011 with around 11 applications still under review. In 2011, two plants in Sweden - Forsmark-1 and Ringhals-4 - have undergone power uprates. Uprating for the country's Oskarshamn-2 has been delayed and is now not expected to be completed until 2015.

Nuclear power plants in European countries, including Bulgaria, Czech Republic, Finland and Spain, have undergone power uprates while others are still seeking approval.

Major restraints

Public attitudes towards nuclear power generation are vital in gaining the necessary acceptance for the successful implementation of PLEX, with the main concern being safety, particularly with regards to the perceived deteriorating performance of plants due to the ageing of components and systems. Ageing effects might lead to potential problems, including embrittlement of reactor pressure vessels, corrosion and stress cracking of pipelines and concrete reinforcements, and the degradation of cables, electronic devices, turbines and other such components.

Life-extension projects need to be undertaken after a careful and thorough analysis of the functionality of the equipment and other operating components, while owners need to win public confidence through open dialogue and transparency. Improving the clarity of safety information would also be helpful.

Opportunities

PLEX provides enormous opportunities for nuclear plant owners, operators and equipment and services supplying companies: the plant owners are responsible for meeting decommissioning costs, which are spread over longer time periods, thus increasing the overall profitability; the plant operators benefit from extended power generation and avoid the costs for new-builds; and there's a potential market for nuclear equipment and services-providing companies in the refurbishment of critical equipment and components. However, the feasibility of undertaking the life extension of a nuclear power plant depends upon the current economic viability of the plant and the extent to which the equipment needs to be replaced.

Meanwhile, an effective PLIM programme involves the integration of operations, maintenance and economic planning to optimise both operating life and plant safety. The benefits of PLIM can be summarised as follows:

• Ageing degradation that can cause ad-hoc functional failure can be identified in time and action taken. This is sometimes called preventative maintenance.
• It helps in ensuring safe operation of the plant over its lifetime and provides increased reliability and reduced O&M cost.
• It identifies the components that are crucial for optimal operation and plant safety.

The implementation of PLIM for long-term operation of the plant requires regulatory as well as political approval, factors that are country-specific. Other prerequisites for implementing a PLIM programme are public acceptance, acceptance by neighbouring countries, and economic viability.