Event Notification Report for April 08, 2024

EN Revision Imported Date: 4/8/2024

EN Revision Text: HPCI DECLARED INOPERABLE

The following information was provided by the licensee via email:

"At 0956 [CST] on November 20, 2023, accumulated gas was identified in the Dresden Unit 2 high pressure coolant injection (HPCI) system discharge header. As a result, the HPCI system was declared inoperable. Since HPCI is a single-train system, this is a condition that could have prevented the fulfillment of a safety function; therefore, this condition is being reported as an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(v)(D). The HPCI system was subsequently vented, and the accumulated gas has been removed, restoring the Dresden Unit 2 HPCI system to an operable status. All other emergency core cooling systems remained operable during this time period.

"There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified."

The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance:
The licensee administratively verified the isolation condenser was operable after declaring HPCI inoperable as required by technical specifications. The licensee stated there was no increase in plant risk. The cause of gas accumulating in the Dresden Unit 2 HPCI discharge header is under investigation, and this issue has been entered into the licensee's corrective action program.

* * * RETRACTION ON 4/5/2024 AT 1544 EDT FROM JON CHAPMAN TO IAN HOWARD * * *

"Further analysis demonstrated that the Unit 2 high pressure coolant injection (HPCI) system remained operable with the level of voiding found in the HPCI discharge line. This analysis also found that the additional loads that would be present if the HPCI system were actuated with this level of voiding are within design limits of the HPCI system piping and supports.

"Based on these results, this event is not reportable under 10 CFR 50.72(b)(3)(v)(D), `Any event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident.' Therefore, EN 56866 submitted on November 20, 2023, is being retracted.

"The NRC Resident Inspector has been notified."

Notified R3DO (Havertape)

ELUATE EXCEEDING PERMISSIBLE CONCENTRATION

The following is a summary of information provided by the licensee via phone and email:

On March 24, 2024, a generator experienced a breakthrough event. The elution from a Curium technetium-99m (Tc-99m) generator did not meet the concentration requirements of 0.15 microcuries molybdenum-99 (Mo-99)/millicurie Tc-99m per 10 CFR 35.204. The generator is from lot number 914024034. The elution contained 1251.3 millicuries of Tc-99m and 203.1 microcuries of Mo-99, resulting in a ratio of 0.16 microcurie Mo-99/millicurie Tc-99m.

The elution was not used to prepare a radiopharmaceutical kit or for dispensing of patient doses. The elution was set aside immediately for decay and disposal. The generator was eluted multiple times following the breakthrough and none of those elutions exceeded the regulatory limit. Curium, the manufacturer, was notified on 3/29/2024. The generator is being quarantined pending disposal.

NOTIFICATION OF UNUSUAL EVENT DUE TO FIRE ALARM IN THE VITAL AREA

The following information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance:

On 4/4/2024 at 1618 MST, a Notification of Unusual Event, HU4.2 was declared based on an unverified fire alarm in the containment building greater than 15 minutes. Palo Verde, Unit 3 was operating in Mode 1 at 91 percent power due to end of cycle coast down to a refueling outage. There is no known plant damage at this time. Offsite assistance cannot enter the containment building, therefore, offsite assistance was not requested. The plant is stable in Mode 1.

The licensee notified State and local authorities and the NRC Senior Resident Inspector.

Notified DHS SWO, FEMA Operations Center, CISA Central, FEMA NWC (email), CWMD Watch Desk (email), DHS NRCC THD Desk (email), and DHS Nuclear SSA (email).

* * * UPDATE ON 04/04/24 AT 2313 EDT FROM YOLANDA GOOD TO IAN HOWARD * * *

The following information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance:

At 2013 MST, Palo Verde Unit 3 terminated the notification of unusual event. The basis for termination was that a containment entry was performed. All levels were inspected, and no fires were found. The NRC Resident Inspector has been notified.

Notified R4DO (Deese), IR-MOC (Crouch), NRR-EO (Felts), DHS SWO, FEMA Operations Center, CISA Central, FEMA NWC (email), CWMD Watch Desk (email), DHS NRCC THD Desk (email), and DHS Nuclear SSA (email).

ITEM RELIED ON FOR SAFETY (IROFS) INOPERABLE

The following information was provided by the licensee via phone and email:

"At approximately 2345 MDT, on 4/1/2024, it was observed that the physical boundary of IROFS10 had been opened while this boundary was being relied upon to perform its safety function. This initial report is being made as a 1-hour notification under Appendix A to 10CFR70 (a)(4). The boundary (an isolation valve) was partially opened inadvertently by contact with adjacent equipment while performing operation of 1003 liquid sampling autoclave. The partially opened valve has been shut, restoring the IROFS10 boundary, and the autoclave has been placed in cooling mode. Out of conservatism, until an extent of condition can be performed, the 1004 autoclave which has a similar design has been taken out of service and placed in cooling mode as well.

"There has been no indication of leakage from any operating liquid sampling autoclave to the environment. The system and plant are in a stable condition."

The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance:

The isolation valve was open less than 30 seconds and there was no exposures to personnel. The licensee will notify the NRC Region.