Since September 11th, public concern in Ireland about Sellafield has taken on the added dimension of fear of a terrorist attack on the plant.
British Nuclear Fuels Ltd now claims to have carried out an analysis which shows that such an attack would not necessarily have severe effects on Ireland.
At a conference in Drogheda at the weekend, BNFL invited the Radiological Protection Institute of Ireland to review the analysis, and we will be taking up this invitation without delay.
The institute's scrutiny will focus on whether a large,
fully-fuelled aircraft could directly impact on the highest-risk plants at the site without resulting in the release to the atmosphere of a very large quantity of radioactivity.
Taking the pessimistic view, that such a release of radioactivity could occur, this article attempts to make a realistic assessment of the damage Ireland might suffer in such an event.
First, would the effects of a terrorist attack be worse than an accident?
Not necessarily. In either case, a large volume of radioactive substances could rise into the atmosphere propelled by an explosion, a fire or both.
The prevailing wind being south-westerly, we might hope that this material would be blown away from us, rather than towards us.
We must assume, however, that we might not be so lucky. In an easterly wind, the cloud of radioactive material would reach the east coast of Ireland in a number of hours, depending on the speed of the wind.
There is undoubtedly a strong segment of opinion among the Irish public that the effects on Ireland of such an event would be so devastating that it would be futile to try to implement any form of protective measures.
It is vital that it be brought home to every member of the public that this would not be the case.
It cannot be emphasised too strongly that there is the world of difference between being at, or very close to, the site of a major nuclear disaster and being 100 miles away, as the nearest point in this country is from Sellafield; or even 60 miles away as we are from Wylfa nuclear power station in north Wales, which is the nuclear installation nearest to Ireland.
At such a distance there is, of course, no possibility of any heat or blast effect, indeed no immediate effect of any kind.
The threat, as stated above, is of airborne radioactivity and, even in the worst case, there will be a period of hours before it arrives.
When the cloud does arrive, there will be no immediate physical ill effects to anybody.
What will occur is exposure to radiation in the atmosphere, in rainfall, in food and in water, resulting in the risk of long-term health effects, most notably increased incidence of cancer in future years.
The risk to any individual will be directly related to the degree of exposure.
It is in keeping this exposure for each individual to a minimum that simple practical precautions will be absolutely vital.
The speedy implementation of basic protective measures in the first hours and the following few days after the event can greatly reduce the exposure of individuals at risk and, therefore, greatly improve the ultimate health outcome for the population.
So clearly then, whether the initiating event is accidental or due to some form of terrorist action, the kind of consequences Ireland could suffer are essentially the same - exposure of people some hours later to radiation in the atmosphere.
In a plan to respond to this situation, the key element will be skill in determining from weather data and data from the affected plant:
how long the cloud will take to reach Ireland;
how severe will radiation levels be when the cloud arrives;
what places will be affected and for how long.
Once radiation arrives, the national network of radiation monitoring stations, supplemented by mobile monitoring units of the Defence Forces and Civil Defence, will enable movement of the radiation cloud to be tracked and radiation levels in each area to be quantified.
The most important thing people can do to minimise their exposure in the initial period will be to stay indoors.
Advice, based on knowledge of the radiation levels in a particular area, will be issued on local and national radio as to when it is most important to remain inside, and for how long.
Prominence has been given to the use of iodine tablets as a means of limiting radiation dose.
Tablets containing non-radioactive iodine, taken just before or at an early stage of exposure, are effective in blocking the uptake of radioactive iodine by the thyroid gland and thereby greatly reducing the risk of thyroid cancer in subsequent years.
Iodine tablets, however, are relevant only to circumstances where radioactive iodine is present and this is not always the case.
Most of the plants at Sellafield, for instance, because of their nature, do not contain radioactive iodine and iodine tablets would, therefore, have no place in the response to a disaster involving these plants.
In certain other circumstances, their availability could, of course, be very important.
It is understood to be the Government's intention that very shortly iodine tablets will be available to everybody to keep in their home, with reserve supplies also being held in key locations throughout the country.
Avoiding consumption of contaminated food would be another essential element in the response to the emergency.
This would most immediately affect consumption of fresh milk from cows which had been grazing on contaminated pastures.
Effective restrictions on supply of such milk or other affected foods would have to be put in place.
The considerable numbers of thyroid cancers in children in Belarus and Ukraine following the Chernobyl accident are likely to have been due not alone to the lack of iodine tablets but also to the unrestricted consumption of contaminated food in the immediate aftermath of the accident.
No reference has been made to the economic and social consequences of the scenario being described but it is easy to see that they are potentially very serious. But the first consideration clearly has to be health.
It would be idle to pretend that protection of people from the consequences of such an event is an exact science, or to deny that difficult compromises would be necessary between the effectiveness of precautions against radiation and hardships which these precautions themselves might cause.
But it is of over-riding importance to appreciate that the health consequences would be solely long-term, and, most importantly, that a tightly organised response, as is provided for under the Emergency Plan for Nuclear Accidents, can be highly effective in keeping these consequences to a minimum.
Dr Tom O'Flaherty is chief executive of the Radiological Protection Institute of Ireland and a member of the Government's Emergency Planning Task Force