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Nuclear submarine accident
One of the emergency situations we have to plan for, however unlikely, is an accident involving a nuclear-powered submarine at Portsmouth’s naval base. Homes in Portsmouth have been sent a leaflet about this which can be found on the PORTSAFE page.
Here are some questions you might have about such an incident.
What should I do if there is a nuclear submarine accident at the naval base?
This website, along with our special leaflets, tell you what you should do if there is an incident.
If you are near your home, you should go indoors, close the windows and doors, and listen to the TV, local radio news or go to our website to keep informed about developing news.
If you’re away from home, you should stay indoors wherever you are and wait for information.
Later, we will ask each household to send one person to collect special protective tablets for each family member (see below for more about this).
How will I be informed about an incident and what do I need to do?
If there is a radiation emergency on a nuclear powered vessel in the dockyard the base siren will give the emergency signal by sounding a rising and falling wailing note. You can find out how the problem is being dealt with and what you should do by watching local TV or listening to your local radio station:
- Solent (96.1 FM, 999 MW)
- Ocean FM (96.7, 97.5 FM)
- Wave (105.2 FM)
- The Quay (107.4 FM)
- Express (93.7 FM)
In a radiation emergency you can get further advice by calling Portsmouth City Council’s emergency number: 0800 085 0375.
What is the risk to the public of an accident?
An accident which could put public health at risk is highly unlikely. But it is sensible to develop plans just in case. The navy has extensive arrangements for monitoring to detect any radioactive hazard and, in partnership with local councils, for taking safety measures if the need arises.
What kind of hazards would there be?
In the unlikely event of an accidental release of radioactive material, plans exist for a range of possible hazards, including:
- breathing in radioactive material
- exposure to radioactivity fallen on the ground
- contamination of food
Is there a danger of a nuclear bomb-type of explosion resulting from an accident?
No. A nuclear explosion from the type of reactor fuel the navy operates in its nuclear powered vessels is not possible.
After the Chernobyl nuclear power station accident in 1986, clouds of radioactive material were released. Could that happen here?
The Chernobyl reactor was much bigger than a naval vessel’s nuclear reactor, which is tiny by comparison. Also, the design of the navy’s pressurised water reactors, and their operation, is vastly different. In the extremely unlikely event of an accident involving the release of radioactive material from a submarine the release and the consequences would be very, very much smaller.
How can you predict the consequences ahead of an accident happening?
Predictions are based on detailed and comprehensive assessments of all aspects of design and operation of submarine nuclear reactors. The assessments are conducted using up-to-date techniques and are evaluated independently by experts.
What measures do the safety plans propose and over what area?
In the first instance, a 500 metre area around the submarine will be evacuated and people sent to shelter. This would happen within the dockyard.
In the event of a risk of release of radioactive material outside the dockyard, people living or working within 2km (1 ¼ miles) downwind of the vessel would be advised to stay indoors and take potassium iodate tablets (PITs) that will be supplied.
Some say you are grossly under-estimating the distance at which people will be affected. Is that so?
The recommendation is an area within 2km downwind from the submarine. Monitoring would indicate whether any widening of this zone is needed.
Radiation would not extend very far from the submarine. The range of radioactive contamination would depend on the size of any release and the weather. The concentration of radioactive material in the atmosphere decreases with distance from the submarine.
What are potassium iodate tablets (known as PITs) for?
The natural process of the thyroid gland in the neck is to absorb iodine to make a hormone. Potassium iodate tablets flood the thyroid with stable iodine. This prevents the thyroid from taking up radioactive iodine which could enter the atmosphere as a result of a nuclear accident, and which could cause health problems in later life.
Are the PITs tablets poisonous?
Given in the correct dose, the tablets should have no harmful effect. If radioactive iodine is in the atmosphere then the tablets would have a very beneficial effect.
Do some people suffer ill-effects?
An individual may have an adverse reaction to iodine, but such cases are extremely rare. The benefits of issuing the tablets in the event of a nuclear accident vastly outweigh any adverse reaction that may occur in a small proportion of people.
Is it true that the tablets only work if they are given before the release of radioactive material?
No. Ideally, the tablets should be taken as soon as possible, but they would still have a beneficial effect if given several hours after a release of radioactive material.
How will I get hold of the tablets if they are needed?
You will be able to collect the tablets from sites around the city. You will be advised when and where to collect the tablets through announcements on our website, in local news coverage and other announcements. More details can be found on our website. A leaflet containing the information will also have been delivered to local addresses within this zone.
Do the authorities practise for these emergencies?
Yes. An exercise in preparation for such an accident took place on October 24, 2007 involving the Royal Navy, Portsmouth City Council, the health service, Hampshire Police and other emergency services. This exercise is one of a routine programme of exercises required by the Health and Safety Executive to test for the extremely remote event of a naval nuclear reactor accident.
Has there ever been an accident of the kind featured in the exercise?
No. There has never been an accident involving a Royal Navy submarine that has led to any release from the nuclear reactor. The probability of any accident resulting in even a small release is very low indeed. The type of accident in the exercise is an extremely remote possibility.
Why is there an emergency plan if the chance of an accident is so small?
Even though a nuclear accident is almost inconceivable, the government’s Health and Safety Executive requires, as an added precaution, that the Ministry of Defence has an emergency plan covering the naval base, and that local councils within 2km of the berth of a nuclear vessel also have an emergency plan.
