An Atlantic graveyard for old nuclear subs?

Press, 1 March 1982, Page 18

An Atlantic graveyard for old nuclear subs?

By

PETER DURISCH

in London

Britain's first nuclearpowered submarine, H.M.S. Dreadnought, is likely to be scuttled in the Atlantic where she-will sink to a radioactive grave in the depths. In the middle of the month, the British Government announced that the 80-metre vessel, commissioned in April, 1963, is to be taken out of service. The problem is what to do with the nuclear reactor, which is highly radioactive.

Dreadnought will be tied up for an indefinite period whlie the decision-making process continues,” said a Ministry of Defence spokesman. "The reactor fuel will be taken out and stored. Once she has been deequipped and de-fuelled she will be made totally sea-tight. Her hatches will be welded until we come to a decison.” British authorities are extremely sensitive about the nuclear power units aboard submarines. Almost all information is classified. A spokesman declined to discuss either the problems posed by the Dreadnought or the possible solutions. The power unit was a Westinghouse design bought from the United States, where, there are five de-com-missioned nuclear submarines in the same position as the Dreadnought.

The. world's first nuclearRowered submarine, U.S.S. [autilus, was launched in 1954 and de-commissioned in March, 1980. The Nautilus is to be preserved as. a museum piece, complete with her reactor and other components. The cost of de-contaminating the reactor and preparing her for exhibition is estimated at about $6 million. \ Britain now has 12 nuclearpowered attack submarines in

service plus four Polaris missile vessels. A further four attack boats are under construction. All have British reactors.’ The reactor and propulsion unit occupies about the aft third of each vessel. It is a small-scale pressurised-water reactor which in most cases allows up to 320,000 kilometres of steaming between refuelling. The Dreadnought contains an SSW reactor developed by the Bettis Atomic Power Laboratory, operated by Westinghouse. It is considered, “noisy” by modern anti-submarine standards and this was a major reason for the decision to scrap her. Many components of these reactors are bombarded by fast neutron radiation throughout their working lives. These neutrons cause parts of the reactor — such as the pressure vessel — to become radioactive.

The main problem is a radioactive isotope known as Cobalt 60. As this isotope degrades, it emits beta radiation — electrons which travel only a short distance —. and also gamma rays. In the case of Cobalt 60 these gamma rays are powerful and .thus damaging to human tissue, even at some distance. On the credit side, Cobalt 60 has a “half-life” of only 5.3 years which means that the level of radiation is reduced by half in that time. Thus over 50 years the level would • fall to about a thousandth of the starting strength.; The reactor components also contain lesser amounts of other radioactive isotapes such as Iron 55, Iron 59, Cobalt 58, Chromium 51, Manganese 54, Nickel 59 and Nickel 63. These are not considered major problems because most have a

short “half-life” and are present only in small quantities. The two main options open to the Government are either to store the reactor components on land — perhaps down a mineshaft — or 'simply to scuttle the vessel in deep water. The Americans are producing an environment impact statement on the options. Initial investigation makes scuttling the firm favourite..

The International Atomic Energy Agency has laid down limits for the dumping of radioactive material at sea. This level — not more than 100 curies of beta and gamma radiation per tonne up to a maximum of 1000 tonnes of material — would certainly not be exceeded by the Dreadnought power unit. If a geiger counter is placed in the middle of an open field, it will record some radiation, known as "natural background radiation.” According to the United States Navy, the radiation from dumping a submarine reactor at sea would cause negligible exposure to people, “much less than natural background radiation.” Scuttling also offers two other advantages. It is much the cheapest option and the components of submarine reactors are made from corrosion-resis-tant materials, so release of radiation by corrosion would ■be extremely slow. ,

The British Government is known to be discussing these problems with the Americans. Although no firm decisions have been made on either side of the Atlantic, a resting place for the Dreadnought on the ocean bottom seems highly probable. — Copyright, London Observer Service.