Most of the nuclear power reactors in current operation are Generation II reactor designs. The Generation III designs were developed based on decades of experience with the older Generation II designs. Some of the improvements include better fuel handling technology, more efficient utilization of fuel, superior thermal efficiency and passive nuclear safety systems. The Generation III reactors follow a more standardized design than the old Generation II reactors which reduces capital costs and maintenance expense.
The advanced boiling water reactor (ABWR) is a Generation III reactor designed and first built in Japan for operation in 1996. In 1997, the U. S. Nuclear Regulatory Commission certified the design. The standard design produces about one and a third gigawatts of electricity. The ABWR is available on the commercial power reactor market from GE-Hitachi Nuclear Energy and Toshiba. There are several ABWRs in operation today in Japan and Taiwan. More are on order in other countries such as the U.S. and the U.K.
In the U.K. the Office for Nuclear Regulation and the Environmental Agency carry out generic design assessments (GDA) of proposed nuclear reactors as part of the approval process to assess the safety, security and environmental impacts of reactor designs independently from the applications to build reactors at specific sites.
in April of 2014, the ONR and EA raised questions during the required generic design assessment of a ABWR reactor that is under consideration. The regulators commented that "The definition of the radioactive source term; the nature and amount of radioactivity, is a fundamental part in understanding and therefore being able to control the hazards associated with any nuclear facility. Once defined, it is important that the requesting party is able to demonstrate and justify that this source term is appropriate to be used as the basis for the safety and environmental cases. Failure to adequately define or justify the source term could ultimately mean that the design, operations or controls specified for the UK ABWR may not be soundly based." The term "radioactive source term" refers to the amount of radioactive material released in a nuclear accident.
In January of 2015, GE-Hitachi provided the requested definition and justification. Unfortunately, the regulators said that the response did not satisfy their expectations. They considered this to be a "serious regulatory shortfall". The ONR and EA elevated their concern to the level of a regulatory issue and said that they still expect GE-Hitachi to provide "a suitable and sufficient definition and justification for the radioactive source terms in the UK ABWR during normal operation." In their latest progress report, the regulators stated, "Reactor chemistry is proving to be a very challenging topic for Hitachi-GE, and project risks have been identified during the quarter which challenge whether a meaningful assessment of reactor chemistry during Step 3 can be achieved."
GE-Hitachi responded to the U.K. regulators with the following statement, "The Japanese ABWR reference plant upon which the UK ABWR is based has been designed, constructed and operated in accordance with some of the highest safety and environmental standards. Worker dose and environmental discharges are amongst the lowest of any operational plant in the world." "We are therefore confident that whilst we may have interpreted differently what is required to define and justify the source term within the UK regulatory environment, our proposed ABWR generic design is safe and will meet appropriate UK environmental and safety standards."
This conversation on source terms has been going of more than a year between the U.K. regulators and GE-Hitachi. It will be interesting to see if it is quickly resolved or if it becomes a major impediment to the purchase of and ABWR from GE-Hitachi.
Construction of Advanced Boiling Water Reactor in Taiwan:
