nrc division of spent fuel management reg con 2014utility logo 2013 loading campaign nuhoms ® 61...

YOUR UTILITY LOGO

MONTICELLO NUCLEAR GENERATING PLANT

Dry Fuel Storage Dye Penetrant Test Issue

NRC Division of

Spent Fuel Management

REG CON 2014 Michael Baumann Director – Nuclear Fuel

YOUR UTILITY LOGO Station Goal

•  Maintain a minimum of 664 available locations in the Monticello Spent Fuel Pool to: – Enable one full core offload (484) – Allow pre-staging of new fuel in pool (180) – Allow for an efficient core shuffle evolution

•  2013 Loading Campaign – Load 10 AREVA TN NUHOMS ® 61 BTH Dry Shielded Canisters (DSC)

YOUR UTILITY LOGO 2013 Loading Campaign

Ten canister loading campaign commenced 9/2/2014. Some initial delays, but expected progress: DSC # In-Service

Date Dose (Person-mR) Goal = 500; Stretch Goal = 400

11 9/9/2013 584 12 9/17/2013 510 13 9/26/2013 404 14 10/7/2013 377 15 10/14/2013 417

DSCs 11 through 15 were moved to the Horizontal Storage Modules (HSMs) following completion of loading


Monticello ISFSI


October 17, 2013: NRC Senior Resident Inspector, during break from observing ongoing furmanite repair activities via the Remote Monitoring System (RMS), observes PT exam on final pass of the Outer Top Cover Plate (OTCP) to DSC Shell weld on DSC-16 and questions dwell time(s).


RMS Viewing Station on Refueling Floor


Dye Penetrant Examination Issue DSCs 11-16

From CAP 1402246, NRC Question on DSC PT Examination Times:

“On 10/17/2013 at approximately 1530 NDE was performed on the final pass of the Dry Shielded Canister Outer Top Cover Plate. An NRC inspector observed part of this activity and questioned the ISFSI project team if the dwell and development times were sufficient to meet procedural requirements.”


PT Exam OTCP-to-Shell weld (DSC-15 shown)


10/17/2013: •  Immediate Stop Work Order Issued. Extent of

Condition on DSC-16 (review via RMS video recordings) shows failure to adhere to dwell times on all welds.

10/18/2013: •  Extent of Condition review on all DSCs shows

failure to adhere to dwell times on most PT examinations (6 DSCs x 11 PT exams / DSC = 66 examinations)

•  Operations declares DSCs 11-16 Inoperable, Not Meeting Tech Specs


NUHOMS ® 61 BTH Dry Shielded Canisters Tech Spec 1.2.5: “All DSC closure welds except those subjected to full volumetric inspection shall be dye penetrant tested in accordance with the requirements of the ASME Boiler and Pressure Vessel Code Section III, Division 1, Article NB-5000. The liquid penetrant test acceptance standards shall be those described in Subsection NB-5350 of the Code.”

YOUR UTILITY LOGO DSC Welds

Inner Top Cover Plat c Siphon & Vent Port

Cover Plates

c Outer Top Cover Plate

Test Port Plug c

YOUR UTILITY LOGO DSC Welds

YOUR UTILITY LOGO Path Forward

Initial Path October - December 2013 •  Vendor conducts three sets of demonstration

tests to “qualify” the PT procedure with actual dwell times taken from RMS review

•  Independent review of rigor of interpretation portion of PT exams

•  Root Cause Evaluation Team chartered •  Consultation with AREVA TN and Structural

Integrity Associates (SIA)


•  January – February 2014 –  Xcel Energy NDE Level III review of all examinations

shows many violations of strict procedural requirements beyond dwell times – no confidence or crediting of PT exams

–  NRC Office of Investigation –  Independent PT of DSC-16 OTCP-to-Shell weld

reveals indication determined to be non-relevant after minor conditioning

–  Some OTCP weld depth areas less than 0.500” requirement (measurements taken in Oct 2013 in hot condition were all > 0.500”)

–  Weld head video-tapes reviewed by SIA


March – July 2014: •  Weld buildup of OTCP-to-Shell weld of DSC-16

to meet minimum weld depth •  NOS review of entire campaign •  Public Meeting with NRC - 5/14/2014 •  Preparation of Exemption Request

–  ISG-15, Multi-Layer PT, Stress Allowable Reduction Factor = 0.8 –  ER to allow use of Stress Allowable Reduction Factor = 0.7 with

valid VT, no PT

•  Exemption Request Submitted on 7/16/2014


August 2014 - Today: •  Request for Supplemental Information (RSI)

received from NRC on September 11th •  NRC Public Meeting to Discuss RSI on

September 24th •  Contracted SIA to develop Finite Element

Model of ITCP and OTCP welds to support RSI Responses

•  Response to RSI Submitted on November 3rd •  NRC Public Meeting held November 18th

YOUR UTILITY LOGO Lessons Learned

Root Cause Evaluation Results: Root Cause: – Xcel Energy management has not implemented adequate controls and ownership to ensure performance by the prime contractor meets Xcel standards and expectations. (RC)


RCE Results: Contributing Cause: The roles and responsibilities of prime contractor supervision (superintendent, general foreman, foreman), including oversight responsibilities, have not been defined and effectively communicated by prime contractor management. (CC1) Contributing Cause: Prime contractor management has not implemented controls and monitoring to adequately ensure performance by their supplemental personnel is within Xcel Energy standards and expectations. (CC2)


RCE Results: Contributing Cause: Adequate time is not allotted for prime contractor supervision (superintendent, foremen, and general foremen) job preparation including review of work packages and pre-job walk downs prior to the commencement of work. (CC3) Contributing Cause: Experience requirements for work planners do not include experience in planning major construction activities (e.g., constructability, demolition, construction testing, pre-operational testing). (CC4)

YOUR UTILITY LOGO Challenges

DSC-16 remains in Transfer Cask on Refueling Floor

Potential issue for 2015 Refueling Outage, working on Contingencies

DSCs 11–15 remain in their respective HSMs

nrc division of spent fuel management reg con 2014utility logo 2013 loading campaign nuhoms ® 61...

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