Yes, as I thought a totally unrealistic limit which needs revision to something workable but safe.  If nuclear subs use a sensible limit why not adopt that instead of spending/wasting billions in over specifications?

There are 2 issues here. Safety of personnel and nuclear safety. Personnel safety (mainly radiation dose) is readily achievable as evidenced by the simplified example of the swimming pool and nuclear submarines. Nuclear safety encompasses, for example, reactor containment and plant operation within safe parameters. Amongst others, the nuclear industry works to ALARA - as low as reasonably achievable, so the changes made now are likely to be safety enhancements to protect operators, maintainers and the public.

Yes, as low as reasonably achievable sound good but why not as reasonably economically achievable ALAREA??

Why not sink the whole reactor into the sea and save all the building costs?

Overall personnel and nuclear safety are the same thing. A nuclear power plant has a number of safety risks, some are the same as in conventional thermal (and other) generating stations, falls from height, electric shock, failure of high pressure steam lines etc.

By nuclear safety I assume you are considering containment of the radioactive substances used in the reactor. The level of containment required and the response to accidents is mostly based on the risk of damage to people and property from radiation. A breach of the containment is likely to be due to some other major event which will have other direct consequences, earthquake, tsunami, aircraft impact etc. The reaction to an escape of radioactive material is very dependent on it’s likely effect on the human body. This is where the problems start.

High doses of radiation are definitely dangerous. 10 Sieverts (Sv) in one dose is Fatal. 4 Sv in one dose will require urgent medical treatment with a 50% chance of survival. 100 milli Sieverts (mSv) in one dose will increase the chance of cancer. This information all comes from high doses delivered over a short space of time, mostly from the atom bombs or radiation accidents.

The effects of low doses delivered over time are much less certain. Legislation is based on the Linear No Threshold theory (LNT) and Collective Dose. LNT is based on the assumption that the human response to radiation is linear down to zero dose. The only point of agreement between the pro and anti-nuclear lobbies is that LNT is wrong. The anti-nuclear lobby believes that the effect increase with low dose as this is the only way they can explain things like the Windscale/Selafield cancer cluster. The pro-nuclear group believe that there is a threshold below which there are no harmful effects. Collective Dose is then based on LNT making the assumption that if 10 000 people receive a dose of 1 mSv that is a total dose of 10 Sv and one of them will die as a result.

The greatest problem with defining the effect of low doses delivered over time is natural background radiation. We are receiving natural radiation all the time from cosmic rays, naturally occurring radioactive materials in the ground and naturally occurring radioactive materials in our bodies (mostly potassium 40 and carbon 14). The dose received from this natural radiation varies widely from place to place due to the composition of the rocks and the height. The higher you are the higher the dose from cosmic rays. The dose is still higher if you fly. Typical doses range from 3 – 6 mSv per year. London is around 2 mSv per year, parts of Cornwall receive nearly 8 mSv per year. There are other areas of the world where the levels are much higher 50 mSv per year or more.

If LNT is valid you would expect to find measurable health differences between high and low dose areas, especially as the doses vary by a factor of 10 or more. A lot of studies have been carried out but haven’t found significant, or even any, health differences.

If LNT is not valid this has a major effect on ALARA. As Low As Reasonably Achievable is simply wasting money.

Overall personnel and nuclear safety are the same thing. A nuclear power plant has a number of safety risks, some are the same as in conventional thermal (and other) generating stations, falls from height, electric shock, failure of high pressure steam lines etc.

By nuclear safety I assume you are considering containment of the radioactive substances used in the reactor. The level of containment required and the response to accidents is mostly based on the risk of damage to people and property from radiation. A breach of the containment is likely to be due to some other major event which will have other direct consequences, earthquake, tsunami, aircraft impact etc. The reaction to an escape of radioactive material is very dependent on it’s likely effect on the human body. This is where the problems start.

High doses of radiation are definitely dangerous. 10 Sieverts (Sv) in one dose is Fatal. 4 Sv in one dose will require urgent medical treatment with a 50% chance of survival. 100 milli Sieverts (mSv) in one dose will increase the chance of cancer. This information all comes from high doses delivered over a short space of time, mostly from the atom bombs or radiation accidents.

The effects of low doses delivered over time are much less certain. Legislation is based on the Linear No Threshold theory (LNT) and Collective Dose. LNT is based on the assumption that the human response to radiation is linear down to zero dose. The only point of agreement between the pro and anti-nuclear lobbies is that LNT is wrong. The anti-nuclear lobby believes that the effect increase with low dose as this is the only way they can explain things like the Windscale/Selafield cancer cluster. The pro-nuclear group believe that there is a threshold below which there are no harmful effects. Collective Dose is then based on LNT making the assumption that if 10 000 people receive a dose of 1 mSv that is a total dose of 10 Sv and one of them will die as a result.

The greatest problem with defining the effect of low doses delivered over time is natural background radiation. We are receiving natural radiation all the time from cosmic rays, naturally occurring radioactive materials in the ground and naturally occurring radioactive materials in our bodies (mostly potassium 40 and carbon 14). The dose received from this natural radiation varies widely from place to place due to the composition of the rocks and the height. The higher you are the higher the dose from cosmic rays. The dose is still higher if you fly. Typical doses range from 3 – 6 mSv per year. London is around 2 mSv per year, parts of Cornwall receive nearly 8 mSv per year. There are other areas of the world where the levels are much higher 50 mSv per year or more.

If LNT is valid you would expect to find measurable health differences between high and low dose areas, especially as the doses vary by a factor of 10 or more. A lot of studies have been carried out but haven’t found significant, or even any, health differences.

If LNT is not valid this has a major effect on ALARA. As Low As Reasonably Achievable is simply wasting money.