05000289/LER-2017-001

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LER-2017-001, Low Temperature Over-Pressurization (LTOP) Technical Specification Requirements Were Not Met
Three Mile Island Unit 1
Event date:
Report date:
Reporting criterion: 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
2892017001R00 - NRC Website
LER 17-001-00 for Three Mile Island Unit 1 Regarding Low Temperature Over-Pressurization (LTOP) Technical Specification Requirements Were Not Met
ML17034A372
Person / Time
Site: Three Mile Island, Three Mile Island Unit 1 Exelon icon.png
Issue date: 02/03/2017
From: Callan E W
Exelon Generation Co
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
TMI-17-008
Download: ML17034A372 (4)


comments regarding burden estimate to the FOIA, Privacy and Information Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

05000-289

3. LER NUMBER

2017 001 - 00

A. EVENT DESCRIPTION

Plant Conditions before the event:

Babcock & Wilcox - Pressurized Water Reactor - 2568 MWth Core Power Date/Time: December 5, 2016 / 16:00 hours Power Level: 0% Mode: Cold Shutdown Three Mile Island Unit 1 (TMI-1) was in a cold shutdown condition with the Reactor Coolant System (RCS) depressurized and drained in support of a Reactor Coolant Pump seal package replacement in December 2016. On 12/05/2016 at 04:36, maintenance activities completed and Operations personnel began to fill the RCS to allow the plant to be re-pressurized.

The final fill of the RCS was performed using the RCS Water Level Control procedure (1103-11), that filled the pressurizer to a maximum level of 390 inches. With the pressurizer at 390 inches, the Control Room Supervisor directed the continuation of another operating procedure to shift the Makeup & Purification (MU) system from Shutdown Mode to Low Temperature Overpressure (LTOP) Mode (procedure OP-TM- 211-101). Procedure OP-TM-211-101 provides the guidance and steps to rack-in the breakers for the makeup pumps.

TMI-1 Technical Specification 3.1.12.1 LTOP Protection requires:

3.1.12.1 LTOP Protection If the reactor vessel head is installed and indicated RCS temperature is 5 313°F, High Pressure Injection Pump breakers shall not be racked in unless:

a. MU-V16A/B/C/D are closed with their breakers open, and MU-V217 is closed, and b. Pressurizer level is maintained 5 100 inches. If pressurizer level is > 100 inches, restore level to 5 100 inches within

1 hour
1.157407e-5 days
2.777778e-4 hours
1.653439e-6 weeks
3.805e-7 months

. [For purposes of clarity in this report: MU-V-16A/B/C/D are throttle valves for high pressure injection to RCS; MU-V-217 is the high capacity makeup valve to RCS] The plant condition with the makeup pump breakers racked in and pressurizer level greater than 100 inches went unrecognized as a Technical Specification (TS) violation for approximately

3 hours
3.472222e-5 days
8.333333e-4 hours
4.960317e-6 weeks
1.1415e-6 months

from -16:00 to approximately 19:00. Over this

3 hour
3.472222e-5 days
8.333333e-4 hours
4.960317e-6 weeks
1.1415e-6 months

period, an operations crew turnover occurred. An oncoming crew member questioned the appropriateness of the makeup pump breakers being racked in with pressurizer level greater than 100 inches. The crew rationalized that a pressurizer level of 390 inches with the RCS depressurized and vented would be equivalent to a pressurizer level of 100 inches once the RCS was pressurized. The pressurization of the RCS commenced per procedure 1103-11.

When the RCS was pressurized to -.35-45psig, pressurizer level stabilized at a level greater than 100 inches. The crew recognized this condition was not allowed by Technical Specification 3.1.12.1 and a one comments regarding burden estimate to the FOIA, Privacy and Information Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

05000-289

3. LER NUMBER

2017 - 001 - REV - 00

  • c . , hour clock to exit the condition was entered at 20:27 and immediate action to lower pressurizer level was initiated. At 21:25, pressurizer level was stabilized at less than 100 inches and the Technical Specification action statement was exited.

B. CAUSE OF EVENT

The apparent cause was determined to be inadequate procedure use and adherence fundamentals associated with reviewing, understanding and complying with procedure limitations and precautions. The procedures in use during the violated condition contained guidance to avoid exceeding the LTOP TS requirements.

C. ANALYSIS / SAFETY SIGNIFICANCE

This event had no effect on the health and safety of the public. There were no actual safety consequences for the condition because the Pilot Operated Relief Valve (PORV) was available during the entire time at which the violated TS condition existed. The PORV low pressure set-point for LTOP protection was enabled, operable and available and would have mitigated a potential RCS overpressurization event.

D. CORRECTIVE ACTIONS

Immediate actions were taken to address gaps in understanding.

  • The involved individuals were coached for gaps in accountability with procedure use and adherence fundamentals associated with reviewing, understanding and complying with procedure limitations and precautions. -
  • The applicable procedures will be revised with actionable steps to improve LTOP TS compliance.
  • Complete a performance analysis to determine training needs to improve understanding of the LTOP Technical Specification for various plant conditions.

E. PREVIOUS OCCURENCES

Previous Events Previous Event Review None * Energy Industry Identification System (EllS), System Identification (SI) and Component Function Identification (CFI) Codes are included in brackets, [SI/CFI] where applicable, as required by 10 CFR 50.73 (b)(2)(ii)(-F).