ML050400034

IR 05000318-05-006 - Attachment 'B' - Constellation Presentation - January 28, 2005

ML050400034
Person / Time
Site:	Calvert Cliffs
Issue date:	01/28/2005
From:	Montgomery B NRC/RGN-I/DRS/EFPB
To:
Shared Package
ML050390438	List: ML050400034
References
IR-05-006
Download: ML050400034 (9)

See also: IR 05000318/2005006

Text

Regulatory Performance Meeting

Failure of Atmospheric Dump Valve

Quick-Open Override Relay

Presented by:

Bruce Montgomery, Engineering Manager

January 28,2005

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Background

On January 23, 2004, Calved Cliffs Unit Two Reactor

Tripped on a loss of # 22 Steam Generator Feed Pump

- The Atmospheric Dump Valves (ADVs) and Turbine Bypass

Valves (TBVs) remained open after the,,T, setpoint for clearing

the Quick Open was reached.

A prolonged overcooling of the Reactor Coolant System

Engineered Safety Feature actuations (SGIS and SIAS)

A Loss of Normal Heat Removal

The Quick Open K7 Relay in the Reactor Regulating

System (RRS) failed to operate properly.

- The relay output contacts failed to reposition when the K7 relay

was de-energized at the ,T ,, setpoint

- Internal inspection subsequently found the K7 relay contacts

burned and welded

- The relay contact was underrated for the application.

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Root Cause Analysis (lR200400047)

A multi-discipline Root Cause Analysis Team specifically

addressed the failure of the K7 Relay

- Five root cause teams were formed to ensure thorough analysis

of the initiating event and contributors

Causal Analysis techniques

- Equipment (Kepner-Tregoe Problem Analysis)

- Human Performance (Barrier Analysis, Why Staircase, Problem

Analysis, and Potential Cause Analysis)

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Causes and Contributors

K7 relay contacts underrated for application

- Original design error by vendor ( > 30 years )

- Vendor K7 circuit modification in I992 resulted in increased

contact current (missed opportunity, exacerbated error)

- Design and design verification performed by vendor

Note: Owners acceptance review of modification performed althoug 1

not required in 1992; however, would not be expected to detect this

design error

Contributing Factors that may have prevented the event

- Inadequate use of Operating Experience (Millstone OE)

- Inadequate internal communications (KI Relay)

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Extent of Condition/Cause

- Reviewed control relays for Reactor Regulating,

Reactor Protection, Engineered Safety Features, and

Auxiliary Feedwater Systems

- Reviewed other important (e.g. LONHR) relays

using the CCNPP PRA

- Performed OE searches for adverse trends

Inadequate contact rating

Vendor design errors

No other underrated contacts or adverse

trends were identified

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Immediate Compensatory Measures

Replaced K7 relays on both Units

Reviewed relay design adequacy in the below systems

- Reactor Regulating

- Reactor Protection

- Engineered Safety Features Actuation

- Auxiliary Feedwater Actuation

Reviewed Field Assistance Reports to ensure

recommended actions were acted upon and Issue

Reports written when appropriate

Reviewed 2003 Operating Experience (OE) for proper

analysis of all related issues contained within the OE

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Corrective and Preventive Actions

(All actions are complete unless otherwise noted)

Corrective Actions

- Engineering issued to replace the K7 relay with one suitable for quick

open circuit application

- Modify the K7 relay installation to remove the effects of the underrated

contacts

- Unit One modified and Unit Two will be modified spring 2005 refueling outage

Preventive Actions

- Replace all K7 relays in both units with new Allied Control relays of the

original design when received from the vendor.

- Provided written expectations and training for OE review scope,

focusing on addressing all issues related to a given event

- Includes improved coordination of multiple system OE review.

- Provided written expectations and training for Field Assistance Reports

including Issue Reports for quality issues

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AdditionaI Actio ns

Common Cause Analysis for 2004 LONHR Events

Single Point Vulnerability (SPV) analysis with focus on Loss of

Normal Heat Removal (LONHR)

Preventive Maintenance (PM) template for control relays

- PM changes per the PM template on PRA Significant and SPV

relays

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Develop a Graduated Risk Review Process for external vendor

engineering products to further reduce human performance errors

associated with vendor provided engineering products

Human Performance Tools in Engineering

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Simplified sketch of the Reactor Regulating

System Interface to the Quick Open Circuit

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nADV SVs

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TBV SVs

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K7 contacts shown with RCS temperature greater than 557O F. Below 557' F,

the K7 relay is de-energized and the K-7 ADV/TBV contacts are open.

For simplification, only one channel of RRS is shown. 9