2CAN122001, Submittal of 40-Year Containment Building Tendon Surveillance and Concrete Inspection

Submittal of 40-Year Containment Building Tendon Surveillance and Concrete Inspection

ML20349A151
Person / Time
Site:	Arkansas Nuclear
Issue date:	12/04/2020
From:	Keele R Entergy Operations
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
2CAN122001
Download: ML20349A151 (12)

Text

Entergy Operations, Inc.

1448 S.R. 333 Russellville, AR 72802 Tel 479-858-7826 Riley Keele, Jr.

Manager, Regulatory Assurance Arkansas Nuclear One 10 CFR 50.55a 2CAN122001 December 14, 2020 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001

Subject:

40-Year Containment Building Tendon Surveillance and Concrete Inspection Arkansas Nuclear One - Unit 2 NRC Docket Nos. 50-368 Renewed Facility Operating License No. NPF-6 Entergy Operations, Inc. (Entergy) completed the Arkansas Nuclear One, Unit 2 (ANO-2) 40-Year Containment Building Tendon Surveillance and Concrete Inspection in accordance with American Society of Mechanical Engineers (ASME)Section XI, Article IWL-2000, as modified by 10 CFR 50.55a and the ANO-2 Technical Specifications (TSs). This inspection was completed on September 25, 2020, upon receipt of the inspection report.

The scope of the inspection was limited to examinations of concrete containment covered under the rules of ASME,Section XI, Subsection IWL. Examination of the containment metallic liner and other Class MC components are accomplished under the rules of ASME,Section XI, Subsection IWE. As such, these examinations are not in the scope of this inspection.

Based on the results of the tendon surveillance and concrete inspection, Entergy concluded that the ANO-2 Containment Building is currently capable of performing its design function and should remain capable of performing its design function until the next scheduled Containment Building Tendon Surveillance and Concrete Inspection (45-Year). Additionally, the observed indications do not show the presence of degradation in accessible areas.

While no indications were found that challenged the current structural integrity or leak tightness of the containment, indications were reported that require evaluation under IWL-3300.

ANO-2 TS 6.6.6, "Containment Inspection Report," requires that any degradation exceeding the acceptance criteria of the containment structure detected during the tests required by the Containment Tendon Surveillance Program shall undergo an engineering evaluation and the results be reported to the NRC within 30 days of the time the evaluation is completed. The evaluation was completed on November 19, 2020.

2CAN122001 Page 2 of 2 Enclosed is a summary of the evaluation of the indications detected during the 40-year ANO-2 Containment Building Tendon Surveillance and Concrete Inspection. This completes the reporting requirements of ANO-2 TS 6.6.6.

This report contains no new regulatory commitments.

If there are any questions or if additional information is needed, please contact Riley Keele, Manager, Regulatory Assurance, at (479) 858-7826.

Respectfully, ORIGINAL SIGNED BY RILEY D. KEELE, JR.

Riley Keele RDK/rwc

Enclosure:

Results of Engineering Evaluation for the ANO-2 40-Year Containment Building Tendon Surveillance and Concrete Inspection cc: NRC Region IV Regional Administrator NRC Senior Resident Inspector - Arkansas Nuclear One NRC Project Manager - Arkansas Nuclear One

Enclosure 2CAN122001 Results of Engineering Evaluation for the ANO-2 40-Year Containment Building Tendon Surveillance and Concrete Inspection

2CAN122001 Enclosure Page 1 of 9 Results of Engineering Evaluation for the ANO-2 40-Year Containment Building Tendon Surveillance and Concrete Inspection Based on the results of the Arkansas Nuclear One, Unit 2 (ANO-2) 40-Year Tendon Surveillance and Concrete Inspection, Entergy concludes that the ANO-2 Containment is currently capable of performing its design function and should remain capable of performing its design function until completion of the next scheduled 45th Year Tendon Surveillance and Concrete Inspection. Additionally, the observed indications do not show the presence of degradation in inaccessible areas.

While no indications were found that challenge current structural integrity or leak tightness of the containment, the following indications were reported that require evaluation under IWL-3300:

Various tendons exceeded the 10% net duct volume difference in grease replacement:

In accordance with IWL-3221.4, the absolute difference between the amount removed and the amount replaced shall not exceed 10% of the tendon net duct volume. If the difference is less than 10%, the condition may be Accepted by Examination. Items that do not meet the acceptance standards of IWL-3221 shall be evaluated as required by IWL-3300 (Reference IWL-3222 for this requirement). V021, V075, V094, V110, and V014 exceeded the 10% net duct volume difference in grease replacement.

Various tendons exceeded the 10% net duct volume difference in grease replacement:

Two Non-Conformance Reports were provided in relation to grease replacement in the tendons.

The first report documents that the 10% net duct volume difference in grease replacement was exceeded for the following tendons.

V021 (11.58%); V075 (13.0%); V094 (15.7%); and V110 (25.3%).

The second report documents that the 10% net duct volume difference in grease replacement was exceeded for V014 (31.1%).

In accordance with IWL-3221.4 (Corrosion Protection Medium),

the corrosion protection medium is acceptable when the reserve alkalinity, water content, and soluble ion concentrations of all samples are within the limits specified in Table IWL-2525-1. The absolute difference between the amount removed and the amount replaced shall not exceed 10% of the tendon net duct volume.

Grease Sample Analysis:

During the inspection of each tendon, a sample of grease was taken and sent off for analysis.

The results of the grease sample analyses are documented in Table 1. For all of the samples, the ion concentration, the water content, and the neutrality were within acceptable limits.

2CAN122001 Enclosure Page 2 of 9 Absolute difference between amount removed and replaced:

For tendons V021, V075, V094, V110, and V014, the absolute difference between the amount removed and the amount replaced exceeded 10% of the tendon net duct volume. Tables 2 and 3 provide a summary of grease replacement volumes. As such, an evaluation in accordance with IWL-3300 must be completed.

In accordance with IWL-3300, the following is considered.

CAUSE OF CONDITION [IWL-3310(a)]:

The cause of the low grease volumes in Tendons V021, V075, and V094 is not known. The most likely cause was leakage of the lower tendon can gasket over time. Another possibility is that the tendon duct was not completely full when installed and over time the column of grease migrated down leaving some measure of incomplete tendon duct fill. For Tendon V014, the majority of the grease loss was a result of grease migrating down the column duct when the bottom cap was removed to inspect the tendon anchorage. At grease refill after the inspection, not all of the grease could be replaced in the tendon duct due to insufficient movement of grease. For Tendon V110, the cause of the low grease volume is known to be from the bottom tendon can gasket failure.

APPLICABILITY OF CONDITION TO THE OTHER UNIT [IWL-3310(b)]:

Both units at ANO are susceptible to leaking tendon gaskets. Based on the results of the tendon surveillances to date, there is no known evidence that indicates that some measure of incomplete tendon duct fill has had an adverse effect on the tendon prestress system. The current required periodic tendon surveillances are considered sufficient to detect any adverse conditions or trends should they develop.

ACCEPTABILITY OF CONTAINMENT [IWL-3310(c)]:

All five tendons listed above had the grease cap removed, were inspected for the presence of water, had a sheathing filler analysis completed, along with anchorage and bearing plate inspections.

As-found tendon grease coverage:

When the grease caps were removed, an inspection was completed of the percentage of grease coverage over all tendon components. All tendon components were 100%

coated with grease. This protective grease coverage demonstrates that even though the tendon duct may not be 100% filled, the protective grease film coverage on the anchorage components is maintained.

Visual inspection for water:

An inspection for water was completed, no water was found.

2CAN122001 Enclosure Page 3 of 9 Tendon buttonhead count:

Each tendon anchorhead was inspected for protruding or broken/missing buttonheads.

No conditions were identified except for V110 which had a missing buttonhead. This condition had already been found in a previous surveillance.

Anchorage corrosion condition:

The tendon anchorage was inspected for signs of corrosion and cracking. No cracking was identified. All corrosion levels are recorded as being Level 1 (Bright Metal, No visible corrosion), Level A (No visible corrosion - Mill oxide coating is in this category),

or Level B corrosion (Rust which appears to have formed prior to initial filler installation and show no evidence of having progressed in the interim).

No tendon end inspected revealed active corrosion on the anchorage components.

Cracks adjacent to bearing plates:

The concrete adjacent to the bearing plates was inspected and no cracks with widths greater than 0.01 were identified.

The acceptance criteria for Tendon Anchorage Areas are given in IWL-3221.3, which is listed below.

(a) There is no evidence of cracking in anchor heads, shims, or bearing plates (b) there is no evidence of active corrosion (c) broken or unseated wires, broken strands, and detached buttonheads were documented and accepted during a pre-service examination or during a previous in-service examination (d) cracks in the concrete adjacent to the bearing plates do not exceed 0.01 in width (e) there is no evidence of free water According to the given criteria, all of the anchorage inspection findings are acceptable.

Based on the acceptable inspection results, it is concluded that the incomplete fill volumes in the tendon ducts of these tendons had no negative effect on the tendons, and there is no indication that the tendons do not have full capacity to maintain the required pre-tensioned force.

2CAN122001 Enclosure Page 4 of 9 REQUIREMENTS FOR REPAIR REPLACEMENT [IWL-3310(d)]:

No repair or replacement activities are required.

ADDITIONAL EXAMINATION REQUIREMENTS [IWL-3310(e)]:

The complete fill volume on tendon V014 was not attained at tendon duct refill. As a result, this tendon will be inspected again at the 45th Year Tendon Surveillance.

Based on the results of the tendon surveillance and concrete inspection, Entergy concluded that the ANO-2 Containment Building is currently capable of performing its design function and should remain capable of performing its design function until the next scheduled Containment Building Tendon Surveillance and Concrete Inspection (45-Year). Additionally, the observed indications do not show the presence of degradation in accessible areas.

2CAN122001 Enclosure Page 5 of 9 TABLE 1 SHEATHING FILLER ANALYSIS - SCOPE TENDONS ION CONCENTRATION (PPM) NEUTRAL

% WATER TENDON END No. (mg CHLORIDE SULFIDE NITRATE CONTENT KOH/g)

SHOP / S < 0.50 < 0.50 < 1.0 < 0.10 48.7 3D107 FIELD / N < 0.50 < 0.50 < 1.0 0.11 64.3 SHOP / SW < 0.50 < 0.50 < 1.0 < 0.10 44.7 3D109 FIELD / N < 0.50 < 0.50 < 1.0 < 0.10 39.0 SHOP / N < 0.50 < 0.50 < 1.0 < 0.10 39.8 3D118 FIELD / S < 0.50 < 0.50 < 1.0 < 0.10 35.0 SHOP / BT < 0.50 < 0.50 < 1.0 < 0.10 55.9 3

31H32 FIELD / BT < 0.50 < 0.50 < 1.0 0.22 13.0 1

SHOP / BT < 0.50 < 0.50 < 1.0 < 0.10 57.7 3

31H45 FIELD / BT < 0.50 < 0.50 < 1.0 < 0.10 48.1 1

SHOP / BT < 0.50 < 0.50 < 1.0 < 0.10 26.4 3

32H33 FIELD / BT < 0.50 < 0.50 < 1.0 < 0.10 30.8 2

SHOP / BT < 0.50 < 0.50 < 1.0 < 0.10 37.4 1

12H23 FIELD / BT < 0.50 < 0.50 < 1.0 < 0.10 41.3 2

SHOP / BT < 0.50 < 0.50 < 1.0 0.10 41.9 3

32H22 FIELD / BT < 0.50 < 0.50 < 1.0 < 0.10 38.9 2

SHOP / 1.0 < 0.50 < 1.0 0.29 16.6 TOP V014 FIELD / < 0.50 < 0.50 < 1.0 0.19 47.7 BOT SHOP / < 0.50 < 0.50 < 1.0 0.30 26.0 V021 TOP

2CAN122001 Enclosure Page 6 of 9 FIELD / < 0.50 < 0.50 < 1.0 < 0.10 21.1 BOT SHOP / < 0.50 < 0.50 < 1.0 < 0.10 24.6 TOP V101 FIELD / < 0.50 < 0.50 < 1.0 < 0.10 23.3 BOT SHOP / < 0.50 < 0.50 < 2.0 2.2 26.7 TOP V075 FIELD / < 0.50 < 0.50 < 1.0 1.7 34.4 BOT SHOP / < 0.50 < 0.50 < 1.0 0.28 29.5 TOP V094 FIELD / < 0.50 < 0.50 < 1.0 < 0.10 35.4 BOT SHOP / N/A N/A N/A N/A N/A TOP V110 FIELD / < 0.50 < 0.50 < 1.0 < 0.10 40.1 BOT TABLE 1 (CONTINUED)

SHEATHING FILLER ANALYSIS - SCOPE TENDONS ACCEPTANCE LIMITS TEST LIMITS Water Soluble Chloride 10.0 (ppm) Maximum Water Soluble Nitrite 10.0 (ppm) Maximum Water Soluble Sulfide 10.0 (ppm) Maximum Water Content 10% Maximum Neutralization No. Greater Than 0 mg KOH/g

2CAN122001 Enclosure Page 7 of 9 TABLE 2 GREASE CAP REMOVAL - SCOPE TENDONS GREASE COATING (%)

TENDON END GREASE BUTTON ANCHOR SHIMS BEARING CAP HEADS HEAD PLATE SHOP / S 100 100 100 100 100 3D107 FIELD / N 100 100 100 100 100 SHOP / SW 100 100 100 100 100 3D109 FIELD / N 100 100 100 100 100 SHOP / N 100 100 100 100 100 3D118 FIELD / S 100 100 100 100 100 SHOP / BT 100 100 100 100 100 3

31H32 FIELD / BT 100 100 100 100 100 1

SHOP / BT 100 100 100 100 100 3

31H45 FIELD / BT 100 100 100 100 100 1

SHOP / BT 100 100 100 100 100 3

32H33 FIELD / BT 100 100 100 100 100 2

SHOP / BT 100 100 100 100 100 1

12H23 FIELD / BT 100 100 100 100 100 2

SHOP / BT 100 100 100 100 100 3

32H22 FIELD / BT 100 100 100 100 100 2

SHOP / 100 100 100 100 100 TOP V014 FIELD / 100 100 100 100 100 BOT SHOP / 100 100 100 100 100 V021 TOP

2CAN122001 Enclosure Page 8 of 9 FIELD / 100 100 100 100 100 BOT SHOP / 100 100 100 100 100 TOP V101 FIELD / 100 100 100 100 100 BOT SHOP / 100 100 100 100 100 TOP V075 FIELD / 100 100 100 100 100 BOT SHOP / 100 100 100 100 100 TOP V094 FIELD / 100 100 100 100 100 BOT

2CAN122001 Enclosure Page 9 of 9 TABLE 3 GREASE CAP REMOVAL - ADDITIONAL TENDONS GREASE COATING (%)

TENDON END GREASE BUTTON ANCHOR SHIMS BEARING CAP HEADS HEAD PLATE SHOP / 100 100 100 100 100 TOP V001 FIELD / N/A N/A N/A N/A N/A BOT SHOP / 100 100 100 100 100 TOP V027 FIELD / N/A N/A N/A N/A N/A BOT SHOP / 100 100 100 100 100 TOP V032 FIELD / N/A N/A N/A N/A N/A BOT SHOP / 100 100 100 100 100 TOP V040 FIELD / N/A N/A N/A N/A N/A BOT SHOP / 100 100 100 100 100 TOP V047 FIELD / N/A N/A N/A N/A N/A BOT SHOP / 100 100 100 100 100 TOP V058 FIELD / N/A N/A N/A N/A N/A BOT SHOP / 100 100 100 100 100 TOP V067 FIELD / N/A N/A N/A N/A N/A BOT SHOP / N/A N/A N/A N/A N/A TOP V110 FIELD / 100 100 100 100 100 BOT