Event Notification Report for July 31, 2014

TRITIUM AND COBALT DETECTED IN GROUND WATER MONITORING WELL

"Voluntary notification per the NEI Groundwater Protection Initiative.

"On July 31, 2014, Callaway Plant received results of a sample from a new ground water monitoring well. The sample was taken on July 25, 2014. The sample results indicated a tritium concentration of approximately 1.6 E6 picocuries/liter and a Co-60 concentration of approximately 12 picocuries/liter.

"The new monitoring well is located within the plant's property and is adjacent to a manhole where the plant's discharge piping joins with the cooling tower blowdown piping. Both the plant discharge piping and the cooling tower discharge piping are buried.

"Releases from the plant discharge line have been suspended. A backup sample taken on July 25, 2014, will be sent to a lab for analysis. Another sample will be taken on August 1, 2014.

"There is no effect on drinking water, and therefore, no dose to the general public or plant staff."

The licensee will notify the Missouri State Department of Natural Resources and Callaway County officials.

The licensee will notify the NRC Resident Inspector.

UNANALYZED CONDITION

"On 07/31/2014 at 1729 PDT, Diablo Canyon Power Plant (DCPP) identified an unanalyzed condition involving the three class 1E 4160 volt buses on Unit 1 and on Unit 2. Following a postulated main steam line High Energy Line Break (HELB) in the Turbine Building, steam could enter the 4160 volt bus rooms through ventilation ducts that exhaust to the turbine deck where the steam lines are located. New analysis identified that the relative humidity (RH) of the 4160 volt bus rooms could reach 100%, which exceeds the design RH used in the analyses for the protective devices in the room. The high-humidity could possibly prevent the protective devices from operating as intended and could therefore result in the unavailability of the 4160 volt buses to supply power to engineered safety feature systems.

"This concern is being reported as an unanalyzed condition per 10 CFR 50.72(b)(3)(ii)(B) and as a condition that could have prevented fulfillment of a safety function per 10 CFR 50.72(b)(3)(v).

"Compensatory measures were taken to isolate the ventilation ducts between the 4160 volt bus rooms and the turbine deck, thereby preventing steam entry into the 4160 volt bus rooms, assuring the protective devices would not be subjected to conditions exceeding the design RH. With this compensatory measure all three 4160 buses on each unit are assured of performing their expected design function following the postulated main steam line break.

"This concern did not result in any adverse affect on the health and safety of the public.

"The licensee informed the NRC Resident Inspector."

In addition to the 10 CFR sections listed in the header of this event notification, the licensee is also reporting this under 10 CFR 50.72(b)(3)(v)(D).

* * * RETRACTION RECEIVED FROM BOB KLINE TO JOHN SHOEMAKER AT 1839 EDT ON 09/24/14 * * *

"Diablo Canyon Power Plant is retracting this event notification based on the following:

"Subsequent to the identification of this event, PG&E conducted additional analysis and testing to support a past operability evaluation. Testing and analysis was completed successfully, demonstrating that the full population of associated components would perform their design safety function in 100% relative humidity conditions during a postulated high energy line break.

"Based on these analysis and testing results, PG&E concludes that the associated equipment remained operable, and did not represent an unanalyzed condition per 10 CFR 50.72(b)(3)(ii)(B) or a condition that could have prevented fulfillment of a safety function per 10 CFR 50.72(b)(3)(v). Therefore, PG&E retracts its notification of 7/31/2014.

"The licensee has notified the NRC Resident Inspector."

Notified the R4DO (Drake).

SERVICE WATER RADIATION MONITOR OUT OF SERVICE FOR MAINTENANCE

"Planned preventative maintenance on the Service Water Radiation Monitor (SWRM) strainer will remove the SWRM from service. As a result, this represents a loss of emergency assessment capability since the SWRM is used to assess NUE and ALERT thresholds. The activity is expected to last 6 hours. During this time, the site will be monitoring alternate indications to detect leakage and the Chemistry Department will perform grab samples as required to ensure the ability to detect NUE levels of radioactivity in a timely manner and protect the health and safety of the public.

"The NRC Resident Inspector has been notified prior to removing the SWRM from service."

HIGH RANGE STACK MONITOR TAKEN OUT OF SERVICE FOR PLANNED MAINTENANCE

At 0825 EDT, Millstone Station Unit 2 removed the Stack High Range Radiation Monitor RM-8168 from service for planned maintenance. Maintenance was completed and operability was restored at 0937 EDT.

The licensee informed both State and local agencies and the NRC Resident Inspector.