Japan Nuclear Technology Institute

・Lack of sufficient manpower for conducting initial fire-fighting efforts
・ Damage to or lack of fire-fighting equipment
・ Delay in reporting the fire to the Fire Department
・ Lack of training among workers involved in initial fire-fighting efforts

・ The in-house fire-fighting corps is assigned the role of using the company’s own defensive means to handle areas that the Fire Department may find difficulty in covering due to time constraints.The corps conducts initial fire-fighting efforts to minimize damage.
・ In a large-scale earthquake and other emergency, there may be times when the Fire Department cannot fulfill its normal operations.The in-house fire-fighting corps must have the ability to handle an anticipated level of fire.

・ Enhancing the initial fire-fighting system (conducting round-the-clock monitoring, securing around ten workers as reserve staff for initial operations, etc.)
・ Improving the reliability of fire-fighting equipment (ensuring anti-quake performance, achieving diversity / multiplexing, etc.)
・ Improving the reliability of associated facilities essential for fire-fighting operations (establishing a direct communications line with the Fire Department at the Main Control Room, securing anti-quake resilience for the emergency management office, etc.)
・ Implementing and reviewing practical drills in coordination with the Fire Department (drawing up a plan for fire-fighting activities, applying the PDCA cycle in drills and their reviews, etc.)

・ Lack of sufficient initial response
・ Difficult-to-understand expressions used
・ Lack of sufficient considerations to the recipients of information
・ Compromise of information liaison attributable to problems with associated facilities or lack of protocols on the part of the power company
・ Problems surrounding NISA’s on-site system for information gathering, liaison and provision

・ Using diverse means to deliver information swiftly to local residents, etc. (issuing press releases from the initial response stage, using various means to repeatedly provide information, etc.)
・Adjusting expressions to provide information in an easy-to-understand manner (citing daily life situations as metaphors, swiftly giving a tentative rating to an event according to the INES scale, etc.)
・ Reinforcing the government’s information liaison / provision system with focus on on-site operations (swiftly dispatching NISA’s senior staff to the site, building a system that automatically gathers important information, etc.)
・ Having nuclear energy operators develop communications facilities and systems that can withstand a major earthquake (improving the installation of such equipment with due considerations to earthquakes, securing staff for measuring and analyzing the leakage of radioactive substances, etc.)
・ Implementing practical drills and trainings (conducting trainings and examination under the partnership of NISA, local government and nuclear energy operators)

・ At the nuclear reactors that were operational or being started up at the time of the earthquake, the detection of “large seismic acceleration” set off a scram signal, which resulted in swift full insertion of all control rods.All operations were implemented appropriately through to the confirmation of sub-criticality.
・ The safety of the reactors that were shut down at the time of the earthquake (Unit 5 and Unit 6) was secured with all control rods in full insertion, and no significant fluctuations observed in the Source Range Neutron Monitor.

・ At the nuclear reactors that were operational or being started up at the time of the earthquake, all heat removal systems were working correctly, and handled all associated operations, such as reactor depressurization, from the reactor scram to cold shutdown.
・ Although the shutdown reactors at Unit 5 and Unit 6 had fuel loaded, all heat removal systems were working correctly.The heat removal system for these Units’ spent fuel pool was also functioning properly.

・ The reactor water and the water of the spent fuel pools were checked for iodine concentration at all Units.Its comparison with pre-quake levels indicated that the earthquake caused no fuel damage.
・ There was no leakage observed in the reactors’ pressure boundaries or in the reactor containment vessels.
・ Radiation monitors indicated no significant increase in all areas except for the reactor buildings’ operation floors.
・ The reactor buildings maintained the negative pressure.
・ No significant fluctuations were reported in the readings at monitoring posts.

・ Facilities that supply external power are required to have the seismic rating of Class C, which is the same as that for general industrial facilities.In this earthquake, three external power systems (two systems subsequently) were secured immediately after the quake despite it having the intensity that surpasses the design-basis seismic motion.
・ The post-quake patrol and subsequently-conducted detailed inspections identified no damage to the emergency D/G, which has the seismic rating of “Class As”.The operation check on the same D/G after the earthquake also confirmed its integrity.This indicates that, even if the earthquake caused the loss of external power sources, the emergency D/G would have secured power supply.

(Lessons learned and future tasks)
　 As detailed above, the functions of “Shut Down”, “Cool”, “Contain” and “Power Supply” were secured in the earthquake.From the perspective of further ensuring safety, it is necessary to acknowledge and address the following lessons learned:
　 1) The method for simulator trainings for plant operators should be reviewed in anticipation of composite events in future earthquakes.
　 2) The staff mobilization system, including the protocol for emergency mobilization, should be developed and reinforced so as to conduct plant operations and on-site checks simultaneously in emergency.
　 3) The emergency D/G should undergo a regular test as soon as the preparation is completed, regardless of its normal frequency for routine tests, from theperspective of ensuring power supply to the plants.

・ The earthquake shifted a heavy item, which subsequently came in contact with the piping for the boric acid solution injection system laid in the room, and damaged the insulation material covering the piping.
・ Although the incident did not damage the piping of the boric acid solution injection system itself, there was a possibility that the heavy item could have damaged other piping with a high level of importance in nuclear safety.

・ The earthquake caused a failure of six of the seven monitors, used to examine radiation contamination of plant operators as they leave a radiologically controlled area.
・ After the earthquake, approximately 400 workers in the radiologically controlled areas of Unit 1 were ordered to evacuate, and rushed to the only available radiation monitor.The radiation control staff had to let the workers leave without undergoing a contamination check through the monitor from the perspective of human safety.
・ The workers were in areas where the level of contamination was kept below the legal limit.Their contamination therefore did not exceed the maximum surface contamination level stipulated by law.However, no contamination checks were conducted following their evacuation to a safe location.

・ While fuel was transported from the reactor to the spent fuel pool at Unit 5 (which was in the shut-down state at the time of the earthquake), it was found that the fuel assemblies had been dislodged from the support fittings on the underside.
・ The records taken during fuel loading indicated that the applicable fuel assembly had the mounting position (vertical) approx. 25mm higher than other assemblies.TEPCO recorded the mounting positions of all fuel assemblies, but did not examine whether the positions were within a specific range.

(Lessons learned and future tasks)
　 Other nuclear power stations must recognize and address the following issues, in addition to lessons learned from non-conformities disclosed by TEPCO as items that require safety considerations:
　 1) The items in temporary storage for use in , must be affixed properly so that they would not damage important equipment in terms of nuclear safety in the event of an earthquake.
　 2) There should be an emergency protocol, stipulating where workers should gather after evacuating from radiologically controlled areas in an earthquake, and how their surface contamination level should be gauged.
　 3) Power stations should control the mounting locations (vertical) of fuel assemblies in fuel loading, and check whether they are properly mounted.

・ Important facilities in terms of nuclear safety (Class 1 facilities in importance-based classification, Class A / As facilities in seismic design classification and other facilities that could affect these facilities) should be subject to inspections and seismic response analysis to determine the effects of earthquakes.The findings from such inspections and analysis should be combined to achieve comprehensive integrity assessment.
Association should be established between the results of inspections and findings from analysis (e.g. implementing a focal inspection in response to the result of analysis) to examine facility integrity in details.
・ Other facilities should be inspected in relevant techniques to assess their integrity.