ML12115A073

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RCS Standpipe White Violation Slides
ML12115A073
Person / Time
Site: Surry Dominion icon.png
Issue date: 04/19/2012
From:
Dominion, Virginia Electric & Power Co (VEPCO)
To:
Division Reactor Projects II
Catherine Morrison
Shared Package
ML12115A066 List:
References
Download: ML12115A073 (32)
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Text

Regulatory Conference R t C Reactor Coolant l tSSystem t

Standpipe Indication Surry Power Station A il 19, April 19 2012 1

Enclosure 2

Introduction N. L.

N L L Larry LLane Site Vice President 2

Enclosure 2

AGENDA Introduction Larry Lane Apparent Violation B L Sonny Stanley B.L.Sonny Risk Assessment John Harrell Management Perspective Larry Lane 3

Enclosure 2

Apparent Violation B. L.

B L Sonny S Stanley St l Director - Station Safety f y and Licensingg 4

Enclosure 2

NRCs Key Points Th Three components t supportt theth violation:

i l ti

  • Failure to distribute a VTM in 2002 and 2003 resulted in the failure to evaluate the applicability of vendor recommended maintenance on the Unit 2 Standpipe
  • As a result of the failure to review the VTM revisions, appropriate instructions to ensure the standpipe is free of foreign matter were not incorporated into procedures
  • The as-found conditions RCS standpipe internals contributed to multiple entries into a reduced inventory configuration 5

Enclosure 2

Apparent Violation Failure to follow VTM Control Procedure results in the failure to evaluate the applicability of vendor recommended maintenance

  • VTM revisions were insignificant
  • VTM recommended maintenance remained unchanged
  • An inappropriately placed blank form in the records package is not acceptable; however, this administrative error had no effect on the standpipe performance 6

Enclosure 2

Apparent Violation The licensee failed to provide detailed written procedures that incorporated appropriate instructions to ensure the RCS standpipe is free of foreign matter

  • The RCS standpipe design change contained the VTM as an attachment and directed maintenance procedures be written
  • Station procedure revised in 1988 to flush and drain the standpipe after use to remove foreign material
  • OEM stated: The process you have in place for the cleaning andd flushing fl hi off ththe SureSite S Sit should h ld provide id you adequate d t maintenance. The flushing of primary grade water through the pipe to flush out the boric acid should be fine in terms of removing i foreign f i matter.

7 Enclosure 2

Apparent Violation The RCS standpipe internals were found to contain rust rust, boric acid residue along its entire length, and a bent float mechanism. This condition contributed to multiple entries into a reduced inventory configuration.

  • Initial disassembly of the standpipe did not identify sufficient foreign material to preclude float movement
  • The internal condition of the standpipe, including the float, did not contribute to erratic indications
  • The erratic indications appear electrical in nature and not associated with the established maintenance strategy
  • Maintenance strategygy on Unit 1 has been successful f

8 Enclosure 2

RCS Configuration fg 9

Enclosure 2

Standpipe p p System y

Main Control Room Containment Alarm Alignment Containment Strip Penetration Indication/ Signal Float Recorder Conditioner Assembly Flagg Assembly Power Power Supply Supply Transmitter 10 Enclosure 2

Instrument Tells Storyy 1st drain 2nd drain down down Trouble shooting, calibration, calibration testing 11 Enclosure 2

Instrument Tells Storyy 12 Enclosure 2

As--Found Conditions As Thin film covering Slight bend in bottom float float assembly compared to new assembly 13 Enclosure 2

As--Found Conditions As Bottom flange of standpipe 14 Enclosure 2

Evaluation of Erratic Indications

  • C Causall evaluation l ti indicated i di t d th thatt th the iissue appeared to be electrical, not mechanical
  • N New flfloat, internal i l cleaning, l i andd new transmitter i

improved performance; however, reduced and less frequent spiking was observed afterward

  • As-found foreign material was minimal
  • Bent float and foreign material did not contribute to erratic indications 15 Enclosure 2

Summary

  • The VTM update p pprocess was not the cause off the Surryy 2 RCS standpipe performance issue
  • The apparent violation is not correct as stated. Procedures were in i place l andd were adequate d t tto minimize i i i fforeign i

material.

  • Thee cause appears appea s to be electrical elect ical in i nature atu e and a d notot a result of foreign material in the standpipe or the condition of the float
  • Therefore, Th f addressing dd i the h violation i l i by b iimplementing l i vendor recommendations, as stated, would not eliminate the erratic indications observed on the Unit 2 standpipe pp
  • Conclusions validated with an independent reviewer 16 Enclosure 2

Updated Risk Assessment John J h HHarrell ll Nuclear Safety f y Engineering g g 17 Enclosure 2

SDP Phase III Assessment

  • Preliminary NRC SDP Results CCDP 4.0E 4.0E-66 Conditional Core Damage Probability CLERP 4.0E-8 Loss of RHR 8%

LOOP 10%

  • Accident Sequences Loss of Inventory 2%

Over Drain-Down LOOP Loss of RHR Over Drain-Down 80%

L Loss off IInventory 18 Enclosure 2

Dominions PRA Assessment

  • Dominions Dominion s risk assessment results in a revised CCDP value Accounts A t for f ththe extensive t i preparations ti t k prior taken i andd during the drain downs and mid-loop operations Accounts for Surry specific HEP values
  • Diagnostic/Symptom Oriented Performance Shaping Factor (PSF) for Procedures
  • High PSF for Experience/Training Considers the most recent industry shutdown events data (2000-2009) 19 Enclosure 2

Extensive Preparations

  • Dominion Fleet Challenge Review
  • Interactions with NRC Region II SRA and Safety Analysis Staff in Rockville
  • Compensatory Measures
  • Contingency Plans 20 Enclosure 2

Surry Specific PSF Change Plant Specific PSF - Procedures NRC assigned Nominal Plant Specific PSFs updated for HEPs using Abnormal Procedures to Diagnostic/Symptom O i t d Oriented

  • 2-AP-16.01, Shutdown LOCA 21 Enclosure 2

Surry Specific PSF Change Plant Specific PSF - Experience/Training NRC assigned Nominal Plant Specific PSF Experience/Training categorized as High

  • Extensive just-in-time training and simulator
  • Data Consistency 22 Enclosure 2

Industry Trend Over Drain-Down Event Resulting in Loss of RHR 6

5 NRC Data Unaccounted for Data 4

GL 88-17, Loss of Decay Heal Removal, October 17, 1988 3

1979-1989 1990-1994 1995-2009 2

OD Events 23 2 0 1

0 1979-1989 1990-1994 2000-2009 23 Enclosure 2

Industry Trend NRC Data Unaccounted for Data Initiating Event Number of Events 1980-1993 1994-2000 2001-2009 LORHR 55 5 5 LOOP 47 12 5 LOI 28 10 7 1979-1989 1990-1994 1995-2009 OD* 23 2 0

  • There were 23 over drain-down events between 1979 and 1989. After which there have been only 2 OD events, one in 1991 and the other in 1992. EPRI TR-1003113 did not calculate an over drain-down initiating event frequency.

24 Enclosure 2

Revised Independent HEPs Significant Independent HEP Comparison Human Error Description NRC HEP Updated Event HEP SD-OD-FEED- Operator Fails to Initiate Feed Before 4.0E-03 1.0E-03 XHE Core Damage During Over Drain-Down Drain Down SD-LOI-DIAG- Operator fails to diagnose Loss of 2.0E-03 5.1E-04 XHE Inventory outside of containment before loss of RHR SD-LOI-ISOL- Operator fail to terminate Loss of 1.2E-04 2.8E-05 AFD-XHE Inventory leak before is depleted SD-XHE-RHR- Operators fail to recover failed RHR 2.2E-01 5.5E-02 RECOV train before RCS boiling SD-RHR-FEED- Operator Fails to Initiate Feed during 4.0E-03 1.0E-03 XHE Shutdown before core damage after RHR failure 25 Enclosure 2

Initiating Event Frequencies

  • NRC used data ffrom EPRI TR-1003113 ((1989-2000))

and NUREG/CR-6144 (1979-1989)

  • Dominion is taking advantage of updated Shutdown Initiating Event Frequencies based on a significant decline in events over the last 20 years.

NRC Dominion Initiating Event (/yr) (/yr)

Loss of Inventory (LOI) 1 3E-01 1.3E-01 1 7E-02 1.7E-02 Loss of RHR (LORHR) 7.9E-02 7.5E-02 LOOP 1.1E-01 8.6E-02 O

Over D i D Drain-Down (OD) 6 6E 03*

6.6E-03* 4 0E 03 4.0E-03

Comparison of Results NRC Phase 3 Results Dominion Results Initiator IE-Freq Duration CCDF CCDP IE-Freq Duration CCDF CCDP

(/yr) (hrs) (/yr) (/yr) (hrs) (/yr)

Loss of RHR 7.9E-02 7 9E-02 39.17 39 17 6 9E-05 3.1E-07 6.9E-05 3 1E-07 7.0E-02 7 0E-02 39 17 39.17 4 1E-06 1.8E-08 4.1E-06 1 8E-08 LOOP 1.1E-01 39.17 9.4E-05 4.2E-07 6.3E-02 39.17 5.0E-06 2.2E-08 Loss of 1.3E-01 39.17 1.4E-05 6.3E-08 3.5E-02 39.17 4.6E-07 2.1E-09 Inventory Over Drain-6.6E-03 2 1.6E-06 3.2E-06 4.0E-03 2 2.6E-07 5.1E-07 Down*

Total 4.0E-06 Total 5.6E-07

  • Over Drain-down is a "per demand" initiating event. For this analysis there were 2 additional drain-down events events.

27 Enclosure 2

Independent Validation

  • Based on a qualitative assessment of the scenarios, the risk f

from this hi performance f deficiency d fi i should h ld beb low l forf theh following reasons:

the pre-evolution pre evolution training leads to a heightened awareness of the importance of maintaining the SDC function the level reduction is performed in a slow and deliberate manner with constant checks to minimize the potential for loss of RHR by over-over draining contingency plans are in place to restore RHR should it be lost.

  • Th The reassessmentt off the th NRC PRA model d l using i revised i d initiating event frequencies and HEPs has demonstrated that the risk from this performance deficiency is small and consistent with a green finding.

28 Enclosure 2

Risk Assessment Results Results - Conditional Core Damage Probabilityy

  • CCDP = 5.6E-7 when considering the additional PRA inputs noted above
  • Therefore, the risk associated with the two entries into midloop operation results in Green risk significance 29 Enclosure 2

Management Perspective Larry Lane L L Site Vice President 30 Enclosure 2

Additional Information f

  • Conceptual Design
  • GEMS Wiring Diagram
  • February Timeline
  • Trend Data
  • Dominion Testing at SCI 31 Enclosure 2
  1. Dominion Instrument Tells Story I - - -

-f

_1_ -

LL I

0 2107 12:00 2108 Absolute Time [M/D h:m]

Enclosure 2

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