05000317/LER-2014-002

LER-2014-002, Condition Prohibited by Technical Specifications Due to Auxiliary Feedwater Train Inoperable Due to Human Performance Error

Calvert Cliffs Nuclear Power Plant, Unit 1
Event date:	02-07-2014
Report date:	04-03-2014
Reporting criterion:	10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
3172014002R00 - NRC Website

A. PRE-EVENT PLANT CONDITIONS:

Unit 1 was in Mode 1 when the event occurred.

B. EVENT:

The subject event involved the mis-positioning of the Auxiliary Feedwater (AFW) mud leg drain isolation valve (1-MS-225) and the mud leg steam trap bypass valve (1-MS-228) on 2/7/2014.

During routine operator rounds, these valves were cycled as required by operating logs, but were not returned to their closed position. During the performance of a scheduled surveillance test (STP-O-9-1, AFAS Logic Test), steam entered the AFW room through the open mud leg drain isolation valves. The affected steam-driven AFW pumps were determined to be inoperable with the mud leg drain isolation valves open. The inoperability lasted for approximately 13 hours1.50463e-4 days <br />0.00361 hours <br />2.149471e-5 weeks <br />4.9465e-6 months <br /> (from the time the mud leg drain isolation valves were left open until they were closed following the surveillance test).

TO THE EVENT:

There were no inoperable structures, components, or systems that contributed to the event.

D. DATES AND APPROXIMATE TIMES OF MAJOR OCCURRENCES:

2/7/14 — 1025 Completed draining the Unit 1 AFW mud legs per the applicable procedure.

Isolation drain valves on the mud legs were inadvertently left open.

2/7/14 — 2205 Unit 1 steam-driven AFW train is declared out-of-service under administrative control for performance of a periodic test in accordance with Technical Specification 3.7.3 Note.

2/7/14 — 2237 During scheduled performance of the surveillance test, when the Auxiliary Feedwater Actuation System signal initiated the steam-driven pumps, steam entered the mud leg drains and exited into the room sump, causing the contents of the sump and steam to be discharged into the AFW pump room.

2/7/14 — 2315 The isolation valves on the mud leg drains were closed and verified at the completion of the scheduled surveillance test. The steam-driven AFW pumps and associated equipment was walked-down and determined to be Operable.

E. OTHER SYSTEMS OR SECONDARY FUNCTIONS AFFECTED:

When steam exhausted into the AFW pump room, the fire alarm was activated. The alarm was reset subsequent to isolating steam to the room. There were no other systems or secondary functions affected. This event is applicable to Calvert Cliffs Nuclear Power Plant, Unit 1 only.

F. METHOD OF DISCOVERY:

The event was self-revealing. When the steam-driven AFW pumps were started for testing, steam was discharged and exited into the room sump, causing the contents of the sump and steam to be discharged into the AFW pump room.

G. MAJOR OPERATOR ACTION:

Following the release of water and steam into the AFW pump room, the affected equipment in the AFW pump room was walked down by a Principal Plant Operator and a Shift Manager.

Only minor wetting of the equipment was found. No other deficiencies were noted. No electrical ground alarms were received in the Control Room. The mud leg isolation drain valves were closed and verified to be closed.

H. SAFETY SYSTEM RESPONSES:

No safety system responses were expected. None occurred.

II. CAUSE OF EVENT:

The cause of the event was human performance related. During normal plant rounds on 2/7/14, the Turbine Building Operator for Unit 1 performed the routine mud leg draining. This task is performed on every shift and requires the Operator to open the mud leg isolation valves and close them at the end of the draining. The evolution typically only takes a few minutes. The Turbine Building Operator is dedicated to the task the entire time. There is a procedure for performing this task, however, in this case, the procedure was not used. An independent Turbine Building Operator. Again, the procedure was not used for this task. The Turbine Building Operators are non-licensed personnel in the Operations Department.

Several human performance error prevention tools were not used during this evolution, including proper use of the procedure and complete three-way communication.

The apparent cause of the event was that the Turbine Building Operators failed to apply human performance tools (procedure use and adherence, and placekeeping) to maintain proper configuration control. Corrective actions were handled through the performance management system and are complete.

A contributing cause was that operations management did not frequently perform observations of routine tasks or conduct unannounced observations. Observation expectations have been established.

The event is documented in station condition report CR-2014-001244.

III. ANALYSIS OF EVENT:

The steam-driven AFW pumps have air cooled bearings, and are in an enclosed, water tight room. If steam is introduced into the room (more than normal leakage) when the steam-driven pump(s) are running, the room temperature would exceed 130 degrees F, the operable limit of the air cooled bearings. Therefore, the steam-driven pumps (and, hence, the steam-driven train) were inoperable during the time the mud leg drain isolation valves were open, since they admitted steam into the AFW pump room.

The Nuclear Regulatory Commission Performance Indicators were not affected by this event.

This event did not result in any actual nuclear safety consequences. The actual consequences of the event were to introduce steam into the AFW pump room. The potential consequence was to introduce steam into the AFW pump room when the steam-driven pumps were needed to respond to an event and the steam-driven AFW pumps would have failed after a period of time.

A risk assessment of the event was performed which resulted in a change in core damage frequency of 3.3E-7 and large early release frequency of 5.1E-8. These changes in risk are well below the threshold for a very low safety significant issue (core damage frequency less than 1E-6 and large early release frequency less than 1E-7).

If an event had occurred for which the AFW pumps would have been required, the safety function of the AFW system would have been performed. In addition to the steam-driven train, there is a 100 percent motor-driven train in a separate location. This train of AFW remained Operable during the time the steam-driven train was rendered inoperable.

Both of the steam-driven AFW pumps were determined to have been inoperable from the time the mud leg drain isolation valves were left open until the time of discovery during the scheduled surveillance test (12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />, 50 minutes).

Technical Specification Condition 3.7.3.0 applies for two AFW pumps inoperable. Technical Specification Condition 3.7.3.0 has several Actions. There are three Actions that have to be performed within an hour. Then one of the AFW pumps has to be restored within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> of entry into Condition 3.7.3.C. Unit 1 was in the Condition for 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />, 50 minutes. The one hour Actions were not performed. Since the one hour Actions were not performed, Technical Specification Condition 3.7.3.E should have been entered. It requires that the Unit be placed in Mode 3 in 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />, and Mode 4 in 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> from entry into the Condition. Unit 1 was not placed in Mode 3 within 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br /> from the time the steam-driven AFW pumps were made inoperable.

Therefore, the condition existed for a time longer than allowed by Technical Specifications.

Per NUREG-1022, Revision 3, a licensee event report is required if a condition existed for a time longer than permitted by the Technical Specifications, even if the condition was not discovered until after the allowable time had elapsed and the condition was immediately rectified upon discovery.

Therefore, the event is reportable pursuant to 10 CFR 50.73(a)(2)(i)(B).

IV. CORRECTIVE ACTIONS:

A. ACTION TO RETURN AFFECTED SYSTEMS TO PRE-EVENT NORMAL STATUS:

1. The mud leg drain isolation valves were closed and verified to be closed.

B. ACTION TAKEN OR PLANNED TO PREVENT RECURRENCE:

1. A Standing Order has been established outlining observation expectations for paired and unannounced observations, as well as expectations for observations of routine evolutions.

2. The human performance errors were handled in accordance with the performance management system and are complete.

A. FAILED COMPONENTS:

None.

B. PREVIOUS LERS ON SIMILAR EVENTS:

A review of Calvert Cliffs events over the past several years was performed. No similar events were found.

C. THE ENERGY INDUSTRY IDENTIFICATION SYSTEM (El IS) COMPONENT

REFERRED TO IN THIS LER:

IEEE 803 IEEE 805

COMPONENT FUNCTION ID SYSTEM ID

AFW mud leg drain valves ISV BA

D. SPECIAL COMMENTS:

None.