KEY POINTS:
Faced with impending energy shortfalls and the need to reduce carbon emissions, many countries are looking again at the nuclear energy option.
Notwithstanding our plentiful renewable energy resources, some New Zealanders are keen for us to do the same. I believe the key issues of safety, nuclear waste management and nuclear proliferation will effectively rule out the adoption of nuclear energy here.
But more immediate practical constraints are the unknowable costs and the non-availability of a suitable reactor.
The New Zealand electricity system has been described as "a small islanded network".
Its 9000 megawatts (MW) of connected generation is small in international terms. It lacks interconnections with other networks, and it has a "long and skinny" configuration with much load and generation centred in the north and south respectively.
Problems with the interisland high-voltage direct current link are but one defect of a grid whose development has not kept pace with the growth of load and generation in both magnitude and regional trends.
Load transfers are constrained at several key points by a lack of transmission capacity. The present limited ability of the network to transmit power from the central North Island area plus power from the south to demand centres in the north is a constraint that has been well publicised.
To guard against its sudden and unexpected loss when fully loaded, the maximum size of an individual generator is dependent on the need for "spinning reserve" on the same side of any constraint in grid transmission, as well as on the need to match the incremental growth of generation with that of load.
Spinning reserve is extra generating capacity, currently unloaded but connected to the grid and able to take up load on demand. The original Huntly Power Station had a total generating capacity of 1000MW, but the rating of each of its four machines is 250MW. Currently the largest single generators on the grid are gas turbines at Otahuhu, Huntly and Taranaki power stations, all in the 380MW to 400MW range.
Were a 1000MW nuclear plant with its single generator to be built in the north it would need as spinning reserve the equivalent of our three largest gas-fired generators. The Electricity Commission has just released draft generation scenarios out to the year 2037 that assume an average demand growth of 200MW a year and a maximum generating unit size of 400MW.
On that basis any nuclear reactor and its associated generator should not be larger, say, than 500MW.
Every country with a civil nuclear power programme has an independent regulating authority responsible for reactor licensing and overseeing all aspects of safety and security. The chief inspector of nuclear installations in Britain said recently: "Our job is about protecting people and society from the hazards presented by the nuclear industry." New Zealand would need one too.
Only three forms of reactor technology are currently in serious contention in Britain, Europe or the United States. All three have evolved from the earliest reactors.
In their most advanced forms, intended for deployment by 2010, these are characterised as Generation III+ reactors. Features shared by all the latest designs include improved safety systems, modular design, increased fuel burn-up, and larger unit size to improve economic competitiveness. Ratings now range from 1200MW to 1725MW. These all include a single massive generator as an integral part of the design.
Stupendous effort is required both to complete one of these complex designs and to progress them through the licensing process of each regulatory regime. The Westinghouse AP1000 was the first Generation III+ reactor to be approved in the US, and an order has just been placed for a pair to be built there.
The evolutionary power reactor (EPR) is a joint design by Areva of France and Siemens. The first such reactor is being built in Finland, due for completion in 2010-11, two years behind schedule and massively over budget. A smaller reactor that is under development in several countries is the pebble bed modular reactor. It has been suggested as suitable for New Zealand conditions but this seems unlikely, given ongoing delays in completing a demonstration plant, absence of operating experience for an unproven design and escalating cost estimates.
There are reports of a bewildering array of small reactor types at varying stages of conceptualisation, design or development around the world. These could be competitive only if produced in large enough numbers.
The exacting requirements for licensing a design make it impossible to forecast when any of these reactors might be available.
New nuclear programmes face massive uncertainties over cost and the need for state subsidies and guarantees.
The British Government recently decided to sponsor a new programme, dependent on the market and not requiring taxpayer support.
Critics say the claim that new reactors can be built without state support is a "fiction". A cost analysis of the storage and disposal of waste concluded that levying the fully commercial price would doom the plan.
The chief executive of German energy giant E. ON, a partner in construction of the Finnish reactor, put the cost per plant at £4.8 billion ($12.5 billion), nearly twice the Government's latest £2.8 billion estimate.
Confusion over capital costs is a major deterrent, but in any case there is no suitable reactor that could be deployed in NZ in the foreseeable future.
Jack Woodward is a professor emeritus at the University of Auckland, a fellow of the Institution of Professional Engineers NZ and past president of Engineers for Social Responsibility.
