Nuclear Energy: The 'Pro' Position

Author: John Walmesley

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The emotional appeal of renewable energy is very strong. Windmills spinning on remote windy shores, solar farms hidden in the vastness of the Northern Cape, wave generators rising and falling with the Atlantic swell. Free energy. An end to ugly coalfired power stations, no more CO2, no more acid rain. No more nukes. It all seems so obvious. Why don’t they just get on with it? In many well-meaning minds, the desire to believe in such a scenario is overwhelming. Such minds filter out and reject any evidence suggesting that it may all be a pipe-dream. The reality is that, particularly in South Africa and certainly at this time, renewables are not a feasible source of bulk electrical energy.

In campaigning for a corner of the market, renewable energy enthusiasts are doing us a disservice. Eskom is already struggling to meet peak demand. Rather soon it will struggle even to meet the base-load requirement. In the next 30 to 40 years, we must build twice as many power stations as there are now operating. All today’s power stations will have to be replaced and load growth will have doubled the output required. That is the daunting reality. There is room for all. Of course we should economise. Of course we should use renewables wherever possible. Solar water heaters should go on every roof. If done magically overnight that would at least give us a couple of years breathing space – but it is not going to happen magically overnight. Strident insistence that renewables are an alternative to coal or nuclear power is clouding the main issue and delaying hard decisions already overdue.

Nuclear power has been with us for 50 years. The debate has been with us for almost as long. Protagonists on both sides repeat themselves ad nauseam. Nobody’s opinion is changed and the public is left wary, even alarmed, and no wiser than before. What really is the case for nuclear?

Renewables simply cannot do the job

The case is straightforward. There is no acceptable alternative. It goes against the grain to knock renewable energy but, for reasons outlined below, it is obvious that renewables are not a viable source of bulk energy in this country at this time. That leaves nuclear energy and, in the South African context, coal – and few would now argue that we can go on indefinitely adding to the 140 million tons we already burn each year. Rather, we should be seeking ways to reduce it. Like all major technologies for power generation, nuclear has its downside, in fact several. Because renewables cannot do the job and because coal is no longer environmentally acceptable, these have to be addressed. The most frequently voiced concerns are discussed below.

The need for a back-up generation

The critical problem with the best developed renewable sources, namely wind and solar power, is availability. Solar units with steerable reflectors may give useful energy for perhaps nine hours per day, wind (on average) for rather less. A windmill designed to give 1800 kilowatts (kW) in a good wind of, say, 14 metres per second (m/s), will drop to only 200kW at 4m/s. Windmills turning in a light wind are barely generating. Even in Demark, a 1000kW windmill will generate on average only 250kW, 25% capacity. Eskom’s three windmills at Klipheuwel, north of Cape Town, have so far managed 17%. Therefore, if solar or wind power is to be used on a significant scale, either a way must be found to store the power overnight (or for periods of calm or light wind) or back-up power stations must be built. Since South Africa appears to have run out of viable pumpedstorage sites, we have no option but to go for back-up power stations, either coal-fired or nuclear.

Coal-fired and nuclear power stations, however, can be run virtually continuously. Since they must be built, if only for backup, why then go to the expense of building the wind or solar installations in the first place? It can easily be shown that the coal or nuclear fuel saved while the wind or solar units are operating nowhere nearly covers the cost of building them.

Denmark

The situation in Denmark illustrates the problem. West Denmark, that excessively windy bit that sticks up into the North Sea, leads the world with over 12% wind power, one windmill for every 600 people. But Denmark has a nice reciprocal arrangement with Norway. When the wind is blowing strongly, power from Denmark is used to pump water into high reservoirs in Norway. When the wind drops, Norway sends hydro-power back to Denmark. When that degree of back-up will no longer suffice, Denmark imports power from Sweden or Germany, much of it nuclear.

South Africa is said to have no further pumped-storage sites for storing power overnight. Neither is there alternative technology for doing so in sight. We have no wealthy neighbours from whom significant quantities of energy can as yet be imported. Neither are there other forms of renewable energy that can provide the necessary back-up. Wave and tide energy are in their infancy and may or may not become economically feasible. Growing biomass to burn consumes vast areas of fertile, watered land. Let the research go on, but we need power now. The only options are coal and nuclear fission and, very expensively for ‘peak-lopping’, gas. If it is accepted that burning even more coal is no longer environmentally acceptable, there remains only the nuclear option.

Objections to nuclear energy

Many concerns are raised by the anti-nuclear lobby – and felt by the general public. Some are rational and demand careful consideration and action. Some are irrational, often stemming from exaggerated fear of radiation assiduously fostered by our small but vocal anti-nuclear movement.

In this connection, it is important to appreciate the role of the National Nuclear Regulator (NNR). Thirty-one countries operate nuclear power stations. Each one has established a national nuclear safety authority, a watch-dog organisation. Based largely on the recommendations of the International Commission on Radiological Protection (ICRP) concerning exposure to ionising radiation, the national bodies establish national safety criteria and monitor operators of nuclear facilities to ensure compliance. The South African nuclear safety authority, the NNR, employs some 60 engineers and scientists working out of offices in Centurion. Eight NNR ‘inspectors’ are currently stationed at Koeberg. In assessing the proposed ‘pebble-bed’ reactor, the NNR is supported by TÜV (Rheinland), a German State licensing authority, and by the British National Nuclear Corporation (NNC).

Issues of concern are listed below, hopefully in order of importance – as perceived by the public. Each warrants a lecture in its own right to substantiate the summary statements made, but that is not feasible in this short article.

Radioactive waste

Low-level waste is buried in carefully designed and sealed trenches at Vaalputs in Namaqualand. There is no possibility of injury to the local population. High-level waste (HLW) consists of spent nuclear fuel or fission products extracted from spent fuel. Its initially extreme ‘toxicity’, unlike the toxicity of chemical waste, diminishes with time at first quickly, but eventually very slowly. Certain isotopes, like most naturally occurring radioisotopes, remain mildly radioactive for millions of years. After a ‘cooling off’ period of some 50 years (which accounts for the lack of urgency in developing national repositories) HLW will be sealed for several thousand years in corrosion-resistant containers. The containers will be sealed into tunnels driven deep into crystalline rock, salt or clay formations carefully selected for zero or minimal groundwater movement. Today’s analyses show that any radiation exposure to groundwater users in the far distant future will be negligible. The waste disposal ‘problem’ is more an issue of public acceptance than of technical difficulty.

Pebble Bed Modular Reactor (PBMR) 165 MWe

The nuclear fuel (452 000 ‘pebbles’ is contained in the reactor pressure valve shown on the left (in red). High-pressure helium gas is heated from 500 to 900 degrees Celsius in passing downwards through the pebble bed. The gas expands through the outlet duct (yellow) to drive the turbine and generator (brown). The gas is then cooled, recompressed and passed back into the pressure valve.Under no circumstances can the ceramic fuel pebbles become hot enough to melt or otherwise to release significant radioactivity: hence the phrase ‘inherent safety’. The reactor pressure vessel is protected from external impact by two metres of reinforced concrete forming the ‘citadel’ (blue). The citadel is surrounded by a building (not shown) itself protected bya further metre of reinforced concrete.

Nuclear accidents

The safety of power reactors, like that of passenger airliners, improves with time. The 1979 Three Mile Island accident (in which no one was hurt) was a wake-up call to the nuclear industry. Major safety improvements were made in what are now called Generation II reactors such as those at Koeberg. They now constitute a tiny risk to the surrounding public well below the NNR criterion limit and far below risks otherwise accepted by the public in daily life. Chernobyl, in 1986, although not technically relevant, was a further shock. Generation III reactors now starting to be built are significantly safer still. In the PBMR pebble-bed reactor, the first of the Generation IV reactors, the risk of a major nuclear accident is eliminated completely.

Nuclear weapons proliferation

Reactors such as Koeberg and the PBMR are in no way associated with weapons. Neither the new nor the spent fuel can be used to make effective ‘explosive devices’. South Africa has shown, however, that given time a country with reasonably sophisticated nuclear technology can, if not subject to international inspection and, if necessary, political intervention, develop that technology to create weapons. This is an urgent and important issue for the world community.

Transport of radioactive materials

Of all objections raised to nuclear energy, the risk associated with nuclear transport is the most over-stated. Since 1971, the world has seen over 20 000 shipments of spent nuclear fuel covering over 30 million kilometres. There have, of course, been ‘incidents’ but never a situation involving over-exposure to radiation.

Radioactive effluents and cancer clusters

Liquid and airborne effluents from nuclear power stations are tightly controlled to very low limits. The environment around all such facilities is continuously monitored. Claims by the anti-nuclear organisations of nearby cancer clusters due to radiation are systematically refuted by local and national health authorities.

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