ML15278A472

UNITED STATES 

NUCLEAR REGULATORY COMMISSION 

OFFICE OF NUCLEAR REACTOR REGULATION 

OFFICE OF NEW REACTORS 

WASHINGTON, DC 20555-0001 

January 15, 2016 

NRC INFORMATION NOTICE 2016-02: IMPROPER SEATING OF REACTOR VESSEL 

SURVEILLANCE CAPSULES 

ADDRESSEES

All holders of an operating license or construction permit for a nuclear power reactor under 

Title 10 of the Code of Federal Regulations (10 CFR) Part 50, “Domestic Licensing of 

Production and Utilization Facilities,” except those that have permanently ceased operations 

and have certified that fuel has been permanently removed from the reactor vessel. 

All holders of and applicants for a combined license, standard design approval, or 

manufacturing license under 10 CFR Part 52, “Licenses, Certifications, and Approvals for 

Nuclear Power Plants.” All applicants for a standard design certification, including such 

applicants after initial issuance of a design certification rule. 

PURPOSE

The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice (IN) to inform 

addressees of recent operating experience related to reactor vessel surveillance capsules that 

were not properly seated in their baskets and subsequently broke loose during plant operation. 

This resulted in the generation of over 200 loose parts in the reactor vessel that adversely 

affected some in-vessel components. 

The NRC expects that recipients will review the information for applicability to their facilities and 

consider actions, as appropriate, to avoid similar problems. However, suggestions contained in 

this information notice are not NRC requirements; therefore, no specific action or written 

response is required. 

DESCRIPTION OF CIRCUMSTANCES

During a refueling outage in April 2015, Sequoyah Nuclear Plant (Sequoyah) identified the 

presence of over 200 loose parts in the Unit 1 reactor vessel. The loose parts consisted of two 

broken surveillance capsules and their contents. Sequoyah reported the condition to the NRC 

on August 7, 2015, in Event Report 51298, in accordance with 10 CFR 21.21, “Notification of 

failure to comply or existence of a defect and its evaluation,” which describes notification 

requirements for defects associated with a condition that, if left uncorrected, could create a 

substantial safety hazard. In addition, this issue was dispositioned as a Green finding with an 

associated non-cited violation in Section 4OA2 of Inspection Report 05000327/2015003; 
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05000328/2015003, “Sequoyah Nuclear Plant – NRC Integrated Inspection Report” 

(Agencywide Documents Access and Management System (ADAMS) Accession 

No. ML15313A244). 

The reactor vessels at the two-unit Sequoyah plant each had eight surveillance capsules that 

were installed inside the vessels during plant construction. The eight surveillance capsules 

were located in alphabetically-labeled locations (S, T, U, V, W, X, Y, and Z). The surveillance 

capsules contain specimens of the material that the reactor vessel was constructed from, which 

the facility periodically removes to test for neutron embrittlement effects on reactor vessel 

material properties. Sequoyah previously withdrew and tested four of the eight Unit 1 

surveillance capsules (from the T, U, X and Y locations) in order to fulfill the surveillance 

capsule withdrawal requirements of 10 CFR 50, Appendix H, “Reactor Vessel Material 

Surveillance Program Requirements,” for a 40-year end-of-life period (32 effective full-power 

years). As part of the license renewal effort for both Sequoyah units, the licensee determined 

that it should relocate two of the remaining four irradiated surveillance capsules from their 

original locations to higher fluence locations within the reactor vessel. 

Sequoyah relocated the two Unit 1 surveillance capsules during a refueling outage in 

November 2013. The surveillance capsule in location S was moved to location T, and the 

surveillance capsule in location W was moved to location X. Following plant startup, the 

licensee determined that a loose part or multiple loose parts were present in the Unit 1 reactor 

vessel, based on abnormal acoustic signals from the loose parts monitoring system. The 

licensee continued to monitor the abnormal acoustic signals over the course of the operating 

cycle and determined that the size of the object(s) decreased, while the frequency of acoustic 

indications increased. 

During the next refueling outage in April 2015, the licensee determined that the source of the 

loose parts was the two irradiated surveillance capsules that had been relocated during the prior 

refueling outage. The capsules were not properly seated in the storage baskets during 

relocation and became dislodged from the baskets during plant operation. This resulted in 

over 200 loose pieces of capsules, spacers, instrumentation parts, and irradiated specimens 

inside the reactor vessel upstream of the fuel assembly nozzles. The licensee removed the 

loose parts from the vessel and the core barrel, lower internals, and lower vessel head. Minor 

wear on vessel internal components was identified. Prior to plant startup, the licensee replaced 

two fuel assemblies due to damage to the fuel assembly nozzle filter screens. 

BACKGROUND

In accordance with Appendix H of 10 CFR Part 50, licensees of reactor vessels with 

end-of-design life neutron fluences that exceed 1.0E17 n/cm2 (E>1 MeV) must monitor their 

beltline materials through a surveillance program. The purpose of these programs is to monitor 

changes in the fracture toughness properties of the ferritic materials in the reactor vessel 

beltline regions that result from exposure of these materials to neutron irradiation and the 

thermal environment. Under the program, surveillance capsules are located in each vessel 

between the core and the reactor vessel in close proximity to the beltline region. 

The types of material specimens contained in the surveillance capsules include Charpy 

specimens, tensile specimens, and (optional) compact fracture toughness specimens. Since 

the surveillance capsules are located closer to the core, they receive higher levels of neutron 

fluence than the reactor vessel. This increase is referred to as the lead factor. The higher 

levels of neutron irradiation received by the surveillance capsule specimens provides insight to 
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projected changes in the fracture toughness properties of the reactor vessel. The surveillance 

capsules are designed and located to permit the relocation or insertion of replacement capsules, 

and capsules may be moved to optimize lead factors. 

Licensees periodically withdraw and test surveillance capsules in accordance with the approved 

withdrawal schedule and the requirements of Appendix H of 10 CFR Part 50. Appendix H of 

10 CFR Part 50 states, in part, that “...the withdrawal program must meet the requirements of 

the Edition of ASTM E 185 [American Society for Testing and Materials E 185, “Standard 

Practice for Design of Surveillance Programs for Light-Water Moderated Nuclear Power Reactor 

Vessels”] that is current on the issue date of the ASME Code to which the reactor vessel was 

purchased. Later editions of ASTM E 185 may be used, but including only those editions 

through 1982.” Capsules beyond the minimum number of capsules described in Table 1 of 

ASTM E 185-82 are designated as standby capsules in the 10 CFR Part 50, Appendix H 

program for the original licensed operating period. 

License renewal and the period of extended operation are discussed in section XI.M31, 

“Reactor Vessel Surveillance,” of NUREG-1801, “The Generic Aging Lessons Learned (GALL) 

Report,” Rev. 2, dated December 2010 (ADAMS Accession No. ML103490041). This section 

states that one surveillance capsule should be withdrawn at an outage in which the capsule 

receives a neutron fluence of between one and two times the peak reactor vessel wall neutron 

fluence at the end of the period of extended operation and be tested in accordance with ASTM 

E 185-82. Therefore, upon receiving a renewed operating license, some surveillance capsules 

previously considered as standby capsules may no longer be considered standby capsules; 

instead, they would be considered part of the Reactor Vessel Surveillance program to meet the 

NUREG-1801, GALL Report guidelines and the 10 CFR Part 50, Appendix H requirements. 

DISCUSSION

The licensee determined that the two irradiated surveillance capsules had not been properly 

seated in their storage baskets when they were relocated during the 2013 refueling outage, 

which allowed them to become dislodged from the baskets during plant operation. Two root 

causes for the event were identified: (1) the use of unapproved actions during relocation of the 

capsules, and (2) an inadequate procedure to verify proper capsule seating after relocation. 

During the removal of access plugs in preparation for relocation of the surveillance capsules, 

workers elected to use an alternate tool since the pneumatic tool that was designed for the task 

was unreliable. This represented a deviation from procedure, but was not recognized at the 

time. The new location for a surveillance capsule was required, by procedure, to be cleaned 

under observation via a camera from an adjacent location. When the camera was installed in 

the closest adjacent location, workers discovered that the location being cleaned was not visible 

from the camera. The procedure was not revised and there was no documentation of this issue 

at the time. Procedural guidance for relocation of the surveillance capsules directed the use of 

the pneumatic tool and observation by camera from an adjacent location. 

When the capsules were relocated, the alternate tool was used rather than the pneumatic tool 

and, similar to the cleaning evolution, installation of the capsule in the new location was not 

visible from the camera. Rather than viewing the actual seating of the surveillance capsules, 

workers used a camera after the tool was removed to check that the capsules were seated. 

The procedure was not changed to reflect these actions and the deviation from procedure was 

not documented. After the capsule was placed in the new location, procedure directed use of 

the loading tool which presses the capsule into place, be monitored via camera from an 
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adjacent location. Again, the procedure could not be accomplished, as written, since the 

location was not visible from the camera, and there was no revision to the procedure or 

documentation of the deviation. 

The procedure included three criteria to monitor for proper capsule seating: (1) hydraulic pump 

pressure, (2) observation of how far recessed into the basket the capsule’s top plug is, and (3) 

observation of the spacing of the capsule’s top plug. The crew did not observe the expected 

hydraulic pump pressure, but implemented an alternate method allowed by the procedure. 

Since the seated capsule could not be viewed by camera from the adjacent location, the crew 

inserted the camera from directly above each relocated surveillance capsule, which did not 

provide a view of how far seated (recessed) into the basket the surveillance capsules were. 

The crew ultimately determined that the relocated surveillance capsules were properly seated. 

The root cause evaluation noted that the pump pressure criteria in the procedure might not be 

an adequate measure of proper seating, whereas the amount a surveillance capsule is 

recessed into the basket is a more definitive measure of proper seating. Additionally, spacing of 

the top plug is the same for a properly seated capsule as it is for one that is simply resting on 

the basket. Thus, two of the three procedure criteria for proper surveillance capsule seating 

were not adequate, and the procedure did not include an accurate way to measure how far the 

top plug was recessed into the basket. 

Several contributing causes were also identified. Field oversight of the work activity was 

inadequate in that there were a number of missed opportunities to identify that the work 

deviated from procedure. The work activity could have been conservatively characterized as 

high risk rather than low risk, which would have resulted in additional reviews before work was 

started and the development of actions to mitigate potential risks. The behaviors associated 

with oversight and risk characterization of the work activity were not reflective of the safety 

culture traits defined in Inspection Manual Chapter 0310, “Aspects Within the Cross-Cutting 

Areas.” Corrective actions to preclude repetition included enhanced oversight requirements and 

inclusion of a physical pull-test for relocated capsules, in addition to visual verification of proper 

surveillance capsule seating. 

Licensees may determine that reactor vessel surveillance capsules must be relocated. This 

operating experience discusses the importance of proper planning, execution, verification, and 

oversight for such an activity. If not properly planned, executed, and verified, relocation of 

reactor vessel surveillance capsules can result in loose parts in the reactor vessel and damage 

to reactor vessel internals, including nuclear fuel assemblies. 

 
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CONTACTS 

This information notice requires no specific action or written response. Please direct any 

questions about this matter to the technical contact listed below or the appropriate Office of 

Nuclear Reactor Regulation (NRR) project manager. 

/RA/ (BAnderson for) /RA/ 

Michael C. Cheok, Director Lawrence E. Kokajko, Director 

Division of Construction Inspection Division of Policy and Rulemaking 

 and Operational Programs Office of Nuclear Reactor Regulation 

Office of New Reactors 

Technical Contacts: Carolyn Fairbanks, NRR 

301-415-6719 

e-mail: Carolyn.Fairbanks@nrc.gov 

Wesley Deschaine, Region II 

404-997-4429 

e-mail: Wesley.Deschaine@nrc.gov 

Note: NRC generic communications may be found on the NRC public Web site, 

http://www.nrc.gov, under NRC Library/Document Collections. 
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CONTACTS 

This information notice requires no specific action or written response. Please direct any 

questions about this matter to the technical contact listed below or the appropriate Office of 

Nuclear Reactor Regulation (NRR) project manager. 

/RA/ (BAnderson for) /RA/ 

Michael C. Cheok, Director Lawrence E. Kokajko, Director 

Division of Construction Inspection Division of Policy and Rulemaking 

 and Operational Programs Office of Nuclear Reactor Regulation 

Office of New Reactors 

Technical Contacts: Carolyn Fairbanks, NRR 

301-415-6719 

e-mail: Carolyn.Fairbanks@nrc.gov 

Wesley Deschaine, Region II 

404-997-4429 

e-mail: Wesley.Deschaine@nrc.gov 

Note: NRC generic communications may be found on the NRC public Web site, 

http://www.nrc.gov, under NRC Library/Document Collections. 

ADAMS ACCESSION NO. ML15278A472 *via e-mail TAC NO. MF6691 

OFFICE NRR/DPR/PGCB Tech Editor* RII/DRP/BR6:BC* NRR/DE/EVIB:BC* NRR/DLR/RARB:BC* 

NAME AGarmoe QTE ABlamey JMcHale DMorey 

DATE 10/06/2015 10/15/2015 12/09/2015 12/09/2015 12/09/2015 

OFFICE NRR/DPR/PGCB* NRR/DPR/PGCB NRR/DPR/PGCP/:BC NRR/DE:D* NRO/DCIP:D 

NAME ABaxter AGarmoe SStuchell MBailey (Acting) MCheok 

(BAnderson for) 

DATE 12/22/15 12/18/2015 12/21/2015 12/29/2015 1/08/2016 

OFFICE NRR/DPR:DD NRR/DPR:D 

NAME AMohseni LKokajko 

DATE 1/ 14 /2016 1/ 15 /2016 

OFFICIAL RECORD COPY