ML12115A073

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RCS Standpipe White Violation Slides
ML12115A073
Person / Time
Site: Surry 
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 Regulatory Conference Conference R

t C

l t S t

R t

C l

t S t

Reactor Coolant System Reactor Coolant System Standpipe Indication Standpipe Indication Surry Power Station A

il 19 2012 April 19, 2012 1

Introduction Introduction N L L L

N. L. Larry Lane Site Vice President 2

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

Apparent Violation Apparent Violation B L S St l

B. L. Sonny Stanley Director - Station Safety and Licensing f y g

4

NRCs Key Points NRCs Key Points Th t

t th i l ti Three components support the violation:

  • Failure to distribute a VTM in 2002 and 2003 resulted in the failure to evaluate the applicability of vendor 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, 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

configuration

Apparent Violation Apparent Violation Failure to follow VTM Control Procedure results in the 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
  • An inappropriately placed blank form in the records package is not acceptable; however, this administrative error had no effect on the standpipe performance 6

Apparent Violation Apparent Violation The licensee failed to provide detailed written procedures 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 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 d fl hi f th S Sit h

ld id d

t and flushing of the SureSite should provide you adequate maintenance. The flushing of primary grade water through the pipe to flush out the boric acid should be fine in terms of i

f i

7 removing foreign matter.

Apparent Violation Apparent Violation The RCS standpipe internals were found to contain rust The RCS standpipe internals were found to contain 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 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 strategy on Unit 1 has been successful 8

gy f

RCS Configuration RCS Configuration f g f g 9

Standpipe System Standpipe System p p y

p p y

Main Control Room Containment Alarm Containment Penetration Alignment Strip Indication/

Recorder Signal Conditioner Flag Float Assembly Power Supply Power Supply g

Assembly Transmitter 10

Instrument Tells Story Instrument Tells Story 2nd drain down 1st drain down Trouble

shooting, calibration calibration, testing 11

Instrument Tells Story Instrument Tells Story 12

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

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

Evaluation of Erratic Evaluation of Erratic Indications Indications Indications Indications C

l l

ti i di t d th t th i

  • Causal evaluation indicated that the issue appeared to be electrical, not mechanical N

fl i

l l i

d i

  • New float, internal cleaning, and new transmitter improved performance; however, reduced and less frequent spiking was observed afterward less frequent spiking was observed afterward
  • As-found foreign material was minimal
  • Bent float and foreign material did not contribute to erratic indications 15

Summary Summary Summary Summary

  • The VTM update process was not the cause of the Surry 2 p

p f

y RCS standpipe performance issue

  • The apparent violation is not correct as stated. Procedures i

l d

d t t i i i f

i were in place and were adequate to minimize foreign material.

  • The cause appears to be electrical in nature and not a e cause appea s to be elect ical i atu e a d ot a result of foreign material in the standpipe or the condition of the float Th f

dd i

h i l i b i l

i

  • Therefore, addressing the violation by implementing vendor recommendations, as stated, would not eliminate the erratic indications observed on the Unit 2 standpipe 16 p p
  • Conclusions validated with an independent reviewer

Updated Risk Assessment Updated Risk Assessment J h H

ll John Harrell Nuclear Safety Engineering f y g

g 17

SDP Phase III Assessment SDP Phase III Assessment SDP Phase III Assessment SDP Phase III Assessment

  • Accident Sequences Conditional Core Damage Probability Loss of RHR 8%

LOOP 10%

  • Accident Sequences Over Drain-Down LOOP Loss of Inventory 2%

LOOP Loss of RHR L

f I Over Drain-Down 18 Loss of Inventory 80%

Dominions PRA Assessment Dominions PRA Assessment

  • Dominions risk assessment results in a Dominion s risk assessment results in a revised CCDP value A

t f th t

i ti t k i

d Accounts for the extensive preparations taken prior and during the drain downs and mid-loop operations Accounts for Surry specific HEP values 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 19 (2000-2009)

Extensive Preparations Extensive Preparations Extensive Preparations Extensive Preparations

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

Surry Specific PSF Change Surry Specific PSF Change Surry Specific PSF Change Surry Specific PSF Change Plant Specific PSF - Procedures 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

Surry Specific PSF Change Surry Specific PSF Change Surry Specific PSF Change Surry Specific PSF Change Plant Specific PSF - Experience/Training 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

Industry Trend Industry Trend Over Drain-Down Event Resulting in Loss of RHR Industry Trend Industry Trend 5

6 NRC Data Unaccounted for Data 3

4 GL 88-17, Loss of Decay Heal Removal, October 17, 1988 1

2 1979-1989 1990-1994 1995-2009 OD Events 23 2

0 0

1 23 1979-1989 1990-1994 2000-2009

Industry Trend Industry Trend Industry Trend 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 24

  • 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.

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

Initiating Event Frequencies Initiating Event Frequencies Initiating Event Frequencies Initiating Event Frequencies

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

(

)

and NUREG/CR-6144 (1979-1989)

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

Initiating Event NRC

(/yr)

Dominion

(/yr)

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

D i D

(OD) 6 6E 03*

4 0E 03 26 Over Drain-Down (OD) 6.6E-03*

4.0E-03

Comparison of Results Comparison of Results Comparison of Results Comparison of Results NRC Phase 3 Results Dominion Results Initiator IE-Freq

(/yr)

Duration (hrs)

CCDF

(/yr)

CCDP IE-Freq

(/yr)

Duration (hrs)

CCDF

(/yr)

CCDP Loss of RHR 7 9E-02 39 17 6 9E-05 3 1E-07 7 0E-02 39 17 4 1E-06 1 8E-08 Loss of RHR 7.9E-02 39.17 6.9E-05 3.1E-07 7.0E-02 39.17 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 Inventory 1.3E-01 39.17 1.4E-05 6.3E-08 3.5E-02 39.17 4.6E-07 2.1E-09 Over Drain-Over Drain-Down*

6.6E-03 2

1.6E-06 3.2E-06 4.0E-03 2

2.6E-07 5.1E-07 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 down events.

27

Independent Validation Independent Validation Independent Validation Independent Validation

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

hi f

d fi i h

ld b l f

h from this performance deficiency should be low for the following reasons:

the pre evolution training leads to a heightened awareness of the

the 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-constant checks to minimize the potential for loss of RHR by over draining

contingency plans are in place to restore RHR should it be lost.

Th t f th NRC PRA d l i

i d

  • The reassessment of the NRC PRA model using revised initiating event frequencies and HEPs has demonstrated that the risk from this performance deficiency is small and 28 consistent with a green finding.

Risk Assessment Results Risk Assessment Results Risk Assessment Results Risk Assessment Results Results - Conditional Core Damage Probability

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

Management Perspective Management Perspective L

L Larry Lane Site Vice President 30

Additional Information Additional Information f

  • Conceptual Design
  • GEMS Wiring Diagram
  • GEMS Wiring Diagram
  • February Timeline
  • Trend Data
  • Dominion Testing at SCI
  • Dominion Testing at SCI 31
  1. Dominion LL I0 Instrument Tells Story I

-f

_1_

Absolute Time [M/D h:m]

2107 12:00 2108

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