05000321/LER-2024-002-01, Incorrectly Installed Temporary Modification Results in Multiple Conditions Prohibited by Plant Technical Specifications
| ML24185A259 | |
| Person / Time | |
|---|---|
| Site: | Hatch  |
| Issue date: | 07/03/2024 |
| From: | Busch M Southern Nuclear Operating Co |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| NL-24-0237 LER 2024-002-01 | |
| Download: ML24185A259 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3212024002R01 - NRC Website | |
text
.&. Southern Nuclear Matt Busch Hatch Nuclear Plant Vice President - Plant Hatch 11028 Hatch Parlcway North Baxley, GA 31513 Jul_y 3, 2024 Docket Nos.: 50-321 50-366 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555-0001 Edwin I. Hatch Nuclear Plant - Unit 1 & 2 Licensee Event Report 2024-002-01 912 537 5859 tel 912 366 2077 fax NL-24-0237 Incorrectly Installed Temporary Modification Results in Multiple Conditions Prohibited by Plant Technical Specifications Ladies and Gentlemen:
In accordance with the requirements of 10 CFR 50.73 (a)(2)(i)(B), Southern Nuclear Operating Company hereby submits the enclosed Licensee Event Report.
This letter contains no NRC commitments. If you have any questions, please contact the Hatch Licensing Manager, Jimmy Collins, at 912.453.2342.
Respectfully submitted, Matt Busch Vice President - Hatch MSB/CJC Enclosure: LER 2024-002-01 Cc:
Regional Administrator, Region II NRR Project Manager - Hatch Senior Resident Inspector - Hatch RTYPE: CHA02.004
Enclosure to NL-24-0237 LER 2024-002-01 Edwin I. Hatch Nuclear Plant Unit 1 & 2 Licensee Event Report 2024-002-01 Incorrectly Installed Temporary Modification Results in Multiple Conditions Prohibited by Plant Technical Specifications Enclosure LER 2024-002-01
Abstract
At 1301 EST on 2/27/2024 while Unit 2 was at 100% power in MODE 1 and Unit 1 was at 0% power in MODE 4, it was discovered that a temporary Plant Service Water (PSW) modification was incorrectly installed on the Bravo condensing unit (CDU) of the Main Control Room Air Conditioning (MCRAC) subsystem. This temporary modification was installed on 1/30/2024 and then removed on 2/28/2024.
For the time period that the incorrectly installed temporary PSW modification was in place, a past operability review (POR) was performed. The POR confirmed that the temporary PSW modification was installed incorrectly, rendering the Bravo MCRAC subsystem inoperable for a period of 29 days. Additionally, it was determined that the Alpha MCRAC subsystem was inoperable due to low refrigerant between 1/25/2024 and 2/8/2024. Due to these inoperabilities, several conditions prohibited by Technical Specifications (TS) were experienced as discussed below. With the removal of the temporary PSW modification on 2/28/2024 the operability of the Bravo MCRAC subsystem was restored. The Alpha MCRAC subsystem was repaired by adding refrigerant on 2/8/2024.
EVENT DESCRIPTION
050 052 I
- 2. DOCKET NUMBER
- 3. LER NUMBER 00366 I
YEAR SEQUENTIAL REV NUMBER NO.
~-I 002 1-0 At 1301 EST on 2/27/2024 while Unit 2 was at 100% power in MODE 1 and Unit 1 was at 0% power in MODE 4, it was discovered that a temporary Plant Service Water (PSW) (EIIS Code: Bl) modification was incorrectly installed on the Bravo condensing unit (CDU) of the Main Control Room Air Conditioning (MCRAC) subsystem (EIIS Code: VI). This temporary modification was installed on 1/30/2024 @ 1020 and then restored on 2/28/2024 @ 1441.
For the time period that the incorrectly installed temporary PSW modification was in place, a past operability review (POR) was performed. The POR confirmed that the temporary PSW modification was installed incorrectly, rendering the Bravo MC RAC subsystem inoperable for a period of 29 days, between 1/30/2024 @ 1020 and 2/28/2024 @ 1441. Additionally, it was determined that the Alpha MCRAC subsystem was inoperable due to low refrigerant between 1/25/2024@ 0416 -
2/8/2024@0410. Due to these inoperabilities, twelve conditions prohibited by Technical Specifications (TS) were experienced as discussed below.
For reference, Unit 1 and Unit 2 share MCRAC and Main Control Room Environmental Control (MCREC) subsystems and have a common refueling floor. Unit 2 was in MODE 1 throughout the duration of these events. Unit 1 was in MODE 1 until 2/4/2024 @ 0008 when it entered MODE 3. Unit 1 was cooled down to MODE 4 on 2/4/2024 @ 0653 and then entered MODE 5 on 2/5/2024 @ 1211. Unit 1 transitioned back to MODE 4 on 2/23/2024 @ 1850.
Prohibited Condition 1 & 2: Unit 1 & Unit 2 were not brought to MODE 3 in 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> as required by TS 3.7.4.E The design of the MCREC system requires one operable MCRAC subsystem per MCREC subsystem. With the Bravo MCRAC subsystem inoperable, the other two subsystems (Alpha and Charlie) have to be in-service to meet the requirements of the MCREC TS condition 3.7.4. The POR revealed that this condition was not continuously met. From 2/1/2024@ 0824 until 2/1/2024@ 2147 all three MCRAC units were inoperable_ Alpha and Bravo were inoperable for reasons discussed above and Charlie was inoperable due to a cooling water tagout. This condition, which resulted in both MCREC trains being rendered inoperable, existed in excess of the Unit 1 & Unit 2 TS condition 3.7.4.E (two MCREC subsystems inoperable) completion time of 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> to be in MODE 3.
Prohibited Conditions 3 & 4: Unit 2 was not brought to MODE 3 in 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> as required by TSs 3.7.4.C and 3.7.5.D Once the Bravo MCRAC unit was rendered inoperable due to the PSW modification, concurrent with the Alpha MCRAC inoperability, one of the MCREC subsystems was rendered inoperable. The required actions for Unit 2 TS conditions 3.7.4.A (one MCREC inoperable) and 3.7.5.B (two MCRAC subsystems inoperable) each have a 7 day completion time.
These completion times began on 1/30/2024 @ 1020 and expired on 2/6/2024 @ 1020 requiring entry into TS conditions 3.7.4.C and 3.7.5.D, each with a 12 hour1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> completion time to be in MODE 3. These completion times expired on 2/6/2024@
2220, but Unit 2 was not brought into MODE 3.
Prohibited Condition 5: Unit 2 was not brought to MODE 3 in 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> as required by TS 3.7.4.E From 2/6/2024 @ 2350 until 2/8/2024 @ 0410, all three MCRAC units were inoperable (Note: Unit 1 was not in a MODE of applicability specified in TS 3.7.4.E during this time). Alpha and Bravo were inoperable for reasons discussed above and Charlie was inoperable due to an electrical bus tagout. This condition, which resulted in both MCREC trains being rendered inoperable, existed in excess of the Unit 2 TS condition 3.7.4.E (two MCREC subsystems inoperable) completion time of 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> to be in MODE 3.
EVENT DESCRIPTION (Continued)
I
- 2. DOCKET NUMBER
- 3. LER NUMBER 00366 I
YEAR SEQUENTIAL REV NUMBER NO.
~-I 002 1-0 Prohibited Conditions 6, 7, 8, 9, 10 & 11: Fuel moves continued in conflict with Unit 1 and Unit 2 TSs 3.7.4.D, 3.7.4.F and 3.7.5.F Additional conditions prohibited by TS existed related to fuel movements that were in progress between 2/7/2024@ 2342 and 2/9/2024@ 2200 when Unit 1 and Unit 2 TS 3.7.4.D, 3.7.4.F and 3.7.5.F required fuel movements to stop immediately.
Unit 1 and Unit 2 TS conditions 3.7.4.A and 3.7.5.B had expired on 2/6/2024@ 1020 and were not exited until 2/10/2024@
1415. Also, Unit 1 and Unit 2 TS condition 3.7.4.F was applicable due to having two MCREC units inoperable between 2/6/2024 @ 2350 and 2/8/2024 @ 0410.
Prohibited Condition 12: Unit 2 was not brought to MODE 3 in 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> as required by TS 3.7.5.D The overlapping time of the inoperabilities of the Alpha and Bravo MCRAC subsystems exceeded the allowable 30 day completion time of the Unit 2 TS condition 3.7.5.A (one MCRAC subsystem inoperable) plus the TS condition 3.7.5.D completion time of 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> to be in MODE 3. TS condition 3.7.5.A began on 1/25/2024@ 0416 and expired on 2/24/2024
@ 0416 requiring entry into TS condition 3.7.5.D which expired on 2/24/2024@ 1616. However, Unit 2 was not brought to MODE 3 in 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> as required.
FAILED COMPONENTS INFORMATION
Master Parts List Number: 1 Z41 B008A & B Manufacturer: Trane Model Number: QB-J299-1 Type: Control Room Condensing Unit
EVENT CAUSE ANALYSIS
The direct cause of the incorrect installation of the temporary PSW modification on the Bravo MCRAC, which rendered it inoperable, was a failure of non-licensed, contract maintenance personnel to use Human Performance (HU) tools to ensure the temporary PSW modification was properly installed per the procedure. Contributing to this, the procedure did not contain adequate steps or guidance for certain aspects of the installation of the temporary PSW modification. The cause of the Alpha MCRAC inoperability was low refrigerant.
SAFETY ASSESSMENT
Due to the issues discussed above, these events are reportable per 10 CFR 50.73 (a)(2)(i)(B) as conditions prohibited by TS. There were no actual safety consequences as a result of this event. At any time while the incorrectly installed temporary modification was installed on the Bravo MCRAC subsystem, either Alpha or Charlie MCRAC subsystems were running or capable of being manually aligned and started to ensure the habitability of the control room was maintained.
Additionally, the Bravo MCRAC system (and therefore at least one MCREC subsystem) was fully functional other than its seismic capability. Given Hatch's seismic zone location, the risk of this scenario is minor. Also, during winter months, the MCRAC heat sink (plant service water) is at a lower temperature, and therefore only one MCRAC subsystem is typically needed to maintain control room cooling.
CORRECTIVE ACTIONS
- 2. DOCKET NUMBER
- 3. LER NUMBER 00366 I
YEAR
[ 2024 I -1 SEQUENTIAL REV NUMBER NO.
002 1-0 With the removal of the temporary PSW modification on 2/28/24 the operability of the Bravo MCRAC subsystem was restored. Although the temporary PSW modification was installed on the other two MCRAC subsystems, a walkdown of these subsystems was performed and no issues were identified. Additional completed corrective actions include: (1) this scenario was added to the Craft On-Boarding Ranking Assessment (COBRA) proficiency assessment, and (2) an SNC Cognizant Person Hold Point/ Sign Off was added in the job plan for this work evolution to validate proper implementation.
Lastly, there is an open action to update the applicable procedure with better detailed instructions for installing the temporary PSW modification. The Alpha MCRAC inoperability was corrected on 2/8/2024 by checking the unit for refrigerant leaks and then restoring proper refrigerant level.
PREVIOUS SIMILAR EVENTS
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