The U.S. nuclear industry, led by the Nuclear Energy Institute, Institute of Nuclear Power Operations, and Electric Power Research Institute, initiated a voluntary effort to integrate and coordinate the industry’s response to the Fukushima Daiichi accident (NEI, 2012). The industry developed the “Diverse and Flexible Coping Strategies (FLEX) Implementation Guide” (NEI, 2012) to satisfy the USNRC’s Mitigation Strategies Order.
FLEX is intended to augment plant coping capabilities (Figure F.1) for external beyond-design-basis (BDB) events. The strategy itself consists of the following four elements:
1. To have portable backup equipment capable of providing water and power to the reactor. Such equipment includes, for example, electrical generators, batteries, and battery chargers; compressors; pumps, hoses, and couplings; equipment for clearing debris; and equipment for temporary protection against flooding;
2. To stage this equipment in locations both onsite and offsite where it will be safe and deployable during a BDB external event;
3. To develop procedures and guidance for implementing FLEX;
4. To develop programmatic controls that will ensure personnel are well trained and equipment is maintained;
FIGURE F.1 FLEX is intended to augment coping capabilities for beyond-design-basis events involving the simultaneous loss of emergency AC power and ultimate heat sink at all units at a nuclear plant, thereby increasing defense in depth. SOURCE: NEI (2012).