In February 2012, during the work related to the irradiated fuel in Unit 5 Reactor Building at Kashiwazaki-Kariwa Nuclear Power Station (boiled water type, rated output: 1,100MW) which was under periodic inspection, the outdoor air isolation damper (valve) of one of the emergency ventilation and air conditioning systems in the Main Control Room^*1 was fully open and unable to close due to the safety mode in operation for inspection. Since the technical specification requires both of the two emergency ventilation and air conditioning systems to be operable, the situation was judged to be a temporary unfulfillment of the operational requirements^*2 on March 2, 2012.

On March 16, 2012, NISA has judged the situation as a noncompliance to the technical specification. After reporting the direct cause, root cause attributed to the organizational system and recurrence prevention measures to NISA, we received a directive document^*3 "Root cause analysis of the noncompliance to the technical specification regarding the operational requirements of the emergency ventilation and air conditioning systems in the Main Control Room in Unit 5 at Kashiwazaki-Kariwa Nuclear Power Station (additional direction)" from NISA on May 16. Based on the direction given, we have further analyzed the root cause of this matter. As a substantial amount of time was required for identifying the issues that lie in each operation process, we requested for postponement of the report due date on July 17 (Report to be submitted by August 13, 2012).

Today, a report including the root cause analysis results and recurrence prevention measures has been submitted to NISA.

After receiving the additional directive document, we have investigated and reorganized the facts by dating back to February 2000 (when the technical specification regarding this matter was first discussed) for the purpose of analyzing a wide variety of background factors contributing to this matter and clarifying the issues. As a result, the following direct issues (that are more specific compared the issues previously reported) have been identified.

- The employees involved did not have the correct understanding of which equipments are subject to the technical specification, as it was not clearly defined in the regulations set under the technical specification (This information is also not clearly defined in several manuals).
- Insufficient reviewing and education due to the lack of clear information.
- The idea that the purpose of the regular inspection was to satisfy the technical specification was not fully shared with departments other than the one that created the process chart.

In response to the issues above, we have attempted to improve awareness of this matter and revised documents such as the "Guide to Applying the Technical Specification" (created internally to support the correct understanding of the technical specification) for the purpose of further improving the understanding of the technical specification. In addition to these measures, the following measures will be implemented as effective recurrence prevention measures for the direct issues identified this time.

- For the lack of clarity, the equipments subject to the technical specification will be clearly defined with reasons, and the employees involved will be educated. Some equipments were not recognized as being subject to the technical specification as the equipments that are regularly used and the equipments for emergency use were mixed, causing confusion among employees and making it difficult to distinguish those subject to the technical specification and those that are not. Providing clear information will prevent such confusion and misunderstanding. (Previously reported)
- Establish information sharing/communication system to ensure the feasibility of validity confirmation of regular inspection process in departments/organizations other than the department which creates the regular inspection process. (Previously reported)
- As the equipments subject to the technical specification were not clearly defined in several manuals, these manuals will be revised as necessary to prevent inconsistencies among one another. (Previously reported)

In our previous report, organizational factors such as operation standardization and improvement and insufficient questioning attitude were identified.
The following three organizational factors (that are more specific compared to those identified in the previous report) have been identified in consideration of the direct issues clarified this time.

- Lack of clarification in the technical specification and other related documents.
- In the process of reviewing the regulations set under the technical specification, the actual issues that the involved employees have were not taken into consideration.
- Dysfunctional information sharing/communication between the equipment maintenance division and the division managing the technical specification regarding the compliance to the technical specification.

The following will be implemented as recurrence prevention measures for the organizational factors.

- The requirements stipulated in the technical specification and related manuals will be reviewed for unclear points. In the event that issues are found with these documents, they will be revised. The documents will be reviewed (and revised if necessary) on a regular basis.
- The equipment maintenance division and the division managing the technical specification will reconfirm their roles related to the technical specification, and construct a functional information sharing/communication system.

Attachment
"Direct Cause, Root Cause Attributed to the Organizational System and Recurrence Prevention Measures Regarding the Technical Specification Noncompliance Related to the operation of the emergency ventilation and air conditioning systems in the Main Control Room in Unit 5 at Kashiwazaki-KariwaNuclear Power Station"(PDF 400KB)

*1 Emergency ventilation and air conditioning systems in the Main Control Room Air conditioning system allowing employees to safely operate equipments/facilitiesand implement necessary measures in the Main Control Room at the time of an accident (without being excessively radiated). There are two systems, with one of which has 100% capacity.
*2 Operational requirements
"Operational requirements" are stipulated by the technical specification regarding the reactor operation. For this case, both of the two emergency ventilation and air conditioning systems (2 fans, a filter, necessary damper (valve) and duct) must be operable when employees engage in work related to irradiated fuel.
*3 Directive document
"Root cause analysis of the noncompliance to the technical specification regarding the operational requirements of the emergency ventilation and air conditioning system in the Main Control Room in Unit 5 at Kashiwazaki-Kariwa Nuclear Power Station (additional direction)" (May 15, 2012 NISA No.20)

The aforementioned documents are available only in Japanese. We apologize for the inconvenience this may cause.