88 F. KOPPENBORG
certifying safety, we use the term to conduct compliance investigations.
(NRA 2014c)
Despite the long-windedness, his response made it clear that “safety” is
hard to achieve in nuclear power. While the NRA aims to reduce the risks,
it simply cannot guarantee absolute safety, if defined as an absence of any
risks. Reducing risks as much as possible crucially depends on what one
understands to be a risk.
Risk assessments are part of the safety review process. Given that
safety requirements for volcanic and earthquake-related risks are of relative nature, the extent of required safety measures depends on the severity
of these risks assumed for a given nuclear reactor. For the earthquake
risk assessment, it is necessary to estimate precisely the maximum amount
of ground movement and, together with that, the maximum amount of
shocks the base of the plant’s facilities must be able to withstand. For such
an estimate, it is important to have a clear grasp of the characteristics of
fault lines where the epicentre of a possible earthquake could be. Safety
measures related to volcanic eruptions depend on the risk posed by volcanoes in the vicinity of the nuclear power plant. This requires a judgement
call about the likelihood of a volcanic eruption. This is not limited to
full-blown eruptions including lava flows, but spewing ash that accumulates on reactor buildings could also be a threat due to the accumulated
weight. One might assume that in a country like Japan, which faces both
earthquakes and active volcanoes regularly, both risks are assessed to be
relatively high.
However, the safety review conducted for the Sendai nuclear plant
in Satsumasendai city, Kagoshima prefecture, suggested otherwise.
According to a critical Japanese expert in seismology, the NRA could
have been stricter in this regard. One problem in seismology as a research
field is that developing precise assessments of the impact of earthquakes
on reactor buildings is an ongoing effort. With no established scientific
consensus, it is possible to portray some fault lines as trivial in estimating the impact on nuclear power facilities (Tateishi 2015). In the
report presented to the NRA, Kyushu EPCO included the most obvious
earthquake sources around the Sendai nuclear power plant. However, it
chose not to include potential others, in particular a fault line off the
coast whose inclusion would have led to stricter earthquake countermeasure requirements. The NRA accepted this conservative interpretation of
certifying safety, we use the term to conduct compliance investigations.
(NRA 2014c)
Despite the long-windedness, his response made it clear that “safety” is
hard to achieve in nuclear power. While the NRA aims to reduce the risks,
it simply cannot guarantee absolute safety, if defined as an absence of any
risks. Reducing risks as much as possible crucially depends on what one
understands to be a risk.
Risk assessments are part of the safety review process. Given that
safety requirements for volcanic and earthquake-related risks are of relative nature, the extent of required safety measures depends on the severity
of these risks assumed for a given nuclear reactor. For the earthquake
risk assessment, it is necessary to estimate precisely the maximum amount
of ground movement and, together with that, the maximum amount of
shocks the base of the plant’s facilities must be able to withstand. For such
an estimate, it is important to have a clear grasp of the characteristics of
fault lines where the epicentre of a possible earthquake could be. Safety
measures related to volcanic eruptions depend on the risk posed by volcanoes in the vicinity of the nuclear power plant. This requires a judgement
call about the likelihood of a volcanic eruption. This is not limited to
full-blown eruptions including lava flows, but spewing ash that accumulates on reactor buildings could also be a threat due to the accumulated
weight. One might assume that in a country like Japan, which faces both
earthquakes and active volcanoes regularly, both risks are assessed to be
relatively high.
However, the safety review conducted for the Sendai nuclear plant
in Satsumasendai city, Kagoshima prefecture, suggested otherwise.
According to a critical Japanese expert in seismology, the NRA could
have been stricter in this regard. One problem in seismology as a research
field is that developing precise assessments of the impact of earthquakes
on reactor buildings is an ongoing effort. With no established scientific
consensus, it is possible to portray some fault lines as trivial in estimating the impact on nuclear power facilities (Tateishi 2015). In the
report presented to the NRA, Kyushu EPCO included the most obvious
earthquake sources around the Sendai nuclear power plant. However, it
chose not to include potential others, in particular a fault line off the
coast whose inclusion would have led to stricter earthquake countermeasure requirements. The NRA accepted this conservative interpretation of