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Proposed Technical Specifications Change TS-505 - Request for License Amendments - Extended Power Uprate(Epu) - Supplement 38, Spent Fuel Pool Criticality Safety Analysis - Updated Information
	ML17062A998
Person / Time
Site:	Browns Ferry ; (DPR-033, DPR-052, DPR-068)
Issue date:	03/03/2017
From:	James Shea; Tennessee Valley Authority
To:	; Document Control Desk, Office of Nuclear Reactor Regulation
References
	CNL-17-035
	Download: ML17062A998 (14)
	v • d • e

Tennessee Valley Authority, 1101 Market Street, Chattanooga, Tennessee 37402 CNL-17-035 March 3, 2017 10 CFR 50.90 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Browns Ferry Nuclear Plant, Units 1, 2, and 3 Renewed Facility Operating License Nos. DPR-33, DPR-52, and DPR-68 NRC Docket Nos. 50-259, 50-260, and 50-296

Subject:

Proposed Technical Specifications (TS) Change TS-505 - Request for License Amendments - Extended Power Uprate (EPU) - Supplement 38, Spent Fuel Pool Criticality Safety Analysis - Updated Information

References:

1. Letter from TVA to NRC, CNL-15-169, "Proposed Technical Specifications (TS) Change TS-505 - Request for License Amendments - Extended Power Uprate (EPU)," dated September 21, 2015 (ML15282A152)

2. Letter from NRC to TVA, Browns Ferry Nuclear Plant, Units 1, 2, and 3 -

Request for Additional Information Related to License Amendment Request Regarding Extended Power Uprate (CAC Nos. MF6741, MF6742, and MF6743), dated June 21, 2016 (ML16154A544)

3. Letter from TVA to NRC, CNL-16-116, "Proposed Technical Specifications (TS) Change TS-505 - Request for License Amendments - Extended Power Uprate (EPU) - Supplement 25,Responses to Requests for Additional Information," dated July 27, 2016 (ML16210A501)

By the Reference 1 letter, Tennessee Valley Authority (TVA) submitted a license amendment request (LAR) for the Extended Power Uprate (EPU) of Browns Ferry Nuclear Plant (BFN) Units 1, 2 and 3. The proposed LAR modifies the renewed operating licenses to increase the maximum authorized core thermal power level from the current licensed thermal power of 3458 megawatts to 3952 megawatts. The Reference 2 letter provided NRC Requests for Additional Information (RAIs) related to spent fuel pool criticality safety analysis. The Reference 3 letter provided responses to NRC RAIs ESGB-RAI 2, ESGB-RAI 3, SFP-RAI 5, SFP-RAI 11, and SFP-RAI 12 from the Reference 2 letter.

Subsequent to the submittal of the Reference 3 letter, as part of implementation of TVA corrective action program actions and as part of the development of the TVA response to NRC Generic Letter 2016-01, Monitoring of Neutron-Absorbing Materials in Spent Fuel Pools, additional information was located related to the responses to NRC RAIs SFP RAI 5 and SFP-RAI 12. As a result, the Enclosure to this letter provides updated responses to NRC RAIs SFP-RAI 5 and SFP-RAI 12. The updated responses to NRC RAIs SFP-RAI 5 and SFP-RAI 12 supersede and replace the associated responses provided in the Reference 3 letter. The remaining RAIs responses from Reference 3 are unchanged.

U.S. Nuclear Regulatory Commission CNL-17-035 Page 2 March 3, 2017 TVA has reviewed the information supporting a finding of no significant hazards consideration and the environmental consideration provided to the NRC in the Reference 1 letter. The supplemental information provided in this submittal does not affect the bases for concluding that the proposed license amendment does not involve a significant hazards consideration. In addition, the supplemental information in this submittal does not affect the bases for concluding that neither an environmental impact statement nor an environmental assessment needs to be prepared in connection with the proposed license amendment.

Additionally, in accordance with 1 O CFR 50.91 (b)(1 }, TVA is sending a copy of this letter to the Alabama State Department of Public Health.

There are no new regulatory commitments associated with this submittal. If there are any questions or if additional information is needed, please contact Mr. Edward D. Schrull at (423) 751-3850.

I declare under penalty of perjury that the foregoing is true and correct. Executed on the 3rd day of March 2017.

Res ectfully,

,wS:L

. Shea President, Nuclear Licensing

Enclosure:

cc: (Enclosure)

Updated Responses to NRC Requests for Additional Information SFP-RAI 5 and SFP-RAI 12 NRC Regional Administrator - Region II NRC Senior Resident Inspector - Browns Ferry Nuclear Plant State Health Officer, Alabama Department of Public Health

ENCLOSURE Updated Responses to NRC Requests for Additional Information SFP-RAI 5 and SFP-RAI 12

ENCLOSURE

E-1 SFP-RAI 5 ANP-3160 states that the Boral is modeled using the design minimum B-10 areal density. The staff was unable to locate information describing how the Boral installed in the BFN SFP racks was verified to meet this minimum value, including any applicable measurement uncertainties.

Provide an explanation of how the minimum B-10 areal density used in the SFP criticality analysis bounds all of the Boral plates installed in the BFN SFP racks.

TVA Response:

In the Reference 1 letter, TVA described the method used to ensure the Boron-10 (B-10) areal density of the Boral plates installed in the BFN SFP racks bounds the minimum areal density specified for the Boral plates (i.e., the minimum B-10 areal density assumed in the SFP criticality safety analysis). Section 3, Materials, of Reference 1 states, in part:

To provide assurance that specification Boral* sheet is utilized during tube fabrication, a special quality control program is in effect at the manufacturers facility. Samples of each Boral sheet are chemically analyzed to determine the B10 content. These data are evaluated to verify that the samples are statistically representative of the entire area of the Boral plate and that B10 content, at a 95% confidence level, meets of exceeds specification requirements. Analyses are also performed to establish the correlation between the B10 content and the thickness of the Boral sample. The Boral sheets are dimensionally inspected and the thickness data are statistically analyzed to verify the sheet meets the minimum thickness requirement over its entire area at a 95%

confidence level. These thickness data are also compared with the correlation data to provide additional assurance that the B10 content meets or exceeds specification requirements. Before each piece of Boral is inserted into a tube assembly it is verified that each inspection has been successfully performed. Presence of the neutron absorber material in the fabricated fuel storage module is verified by dimensional inspection and by visual examination.

Product of Brooks & Perkins, Inc. consisting of a layer of B4C-Al matrix bonded between two layers of aluminum.

Reference

1.

Letter from TVA to NRC, Revised Design Basis And Environmental Assessment for the Proposed High Density Fuel Storage System, dated December 2, 1977 (ADAMS Accession No. 4008006709)

ENCLOSURE

E-2 TVA Response to RAI-SFP 5 Rev. 1:

Since the original response to this RAI was submitted, records were recovered from the manufacturer pertaining to Boral plates utilized in the BFN racks. The BFN SFP racks contain a total of 20,940 Boral plates.

With respect to verifying the minimum B10 areal density of the Boral plates, the associated Contract Specification states Boral plates can be certified by either chemical analysis or neutron transmission/(attenuation) measurement. The minimum required acceptable areal density value is 0.013 B10/cm2 per the associated Contract Specification and the minimum acceptable inspection value is 0.0135 B10/cm2, per the Brooks & Perkins, Inc. inspection procedure.

Utilizing the rack manufacturing data originally documented in support of the TVA response to NRC Generic Letter 2016-01 (TVA letter to NRC, Tennessee Valley Authority (TVA) Response to NRC Generic Letter 2016-01, Monitoring of Neutron-Absorbing Materials in Spent Fuel Pools, dated November 3, 2016 (ML16308A477)), the following histogram can be generated for the 18,572 plates of BFN areal density measurement data.

0 100 200 300 400 500 600 700 800 900 1000 1100 1200 0.013 0.014 0.015 0.016 0.017 0.018 0.019 0.02 0.021 0.022 0.023 0.024 0.025 0.026 BinFrequency ArealDensity(B10/cm2)(BinSize=0.0001)

The minimum measured areal density was 0.0155 B10/cm2. The distribution mean is 0.0192 B10/cm2 with a standard deviation of 0.001088 B10/cm2. The minimum manufactured value is ~20% greater than the contractual manufactured minimum requirement. The

ENCLOSURE

E-3 distribution indicates that the manufacturing process assures the contractual minimum requirement was easily met. It should be noted that the minimum value of 0.013 B10/cm2 is greater than 5 below the mean. Of the remaining 2,368 plates, neutron attenuation data was found for 2,096 plates.

Utilizing the rack manufacturing data originally documented in support of the TVA response to NRC Generic Letter 2016-01 dated November 3, 2016, a histogram can be generated for BFN Neutron Transmission/Attenuation measurements.

0 10 20 30 40 50 60 70 80 90 100 0.84 0.85 0.86 0.87 0.88 0.89 0.9 0.91 0.92 0.93 0.94 0.95 0.96 0.97 0.98 0.99 1

BinFrequency NeutronAttenuation,AbsorptionFraction,(Bin Size=0.001)

The minimum measured Neutron Attenuation fraction was 86.25%. The distribution mean is 93.16% with a standard deviation of 1.693%. While the official Neutron Attenuation B10/cm2 conversion has not been recovered, it should be noted that a fraction of 84% is a little greater than 5 below the mean. The distribution of Neutron Attenuation values is similar to areal density indicating the manufacturing process ensured contractual requirements were met.

Even if all Neutron Attenuation values are assumed to be at the lower areal density bound of 0.013 B10/cm2, it does not automatically mean an additional conservative uncertainty, below the lower bound, is physically meaningful.

There are 272 Boral plates where neither areal density or Neutron Attenuation data could be determined at this time, primarily due to illegible source documents. Because all the plates in

ENCLOSURE

E-4 the BFN SFP racks were manufactured to the same contractual requirements, utilizing the same manufacturing processes, there is reasonable assurance that these remaining plates would lie within the above discussed distributions. Consequently, there is no physical basis for application of uncertainty penalties below 0.013 B10/cm2 (particularly in light of the fact that the minimum pass/fail B10 areal density inspection criterion was 0.0135 B10/cm2).

ENCLOSURE

E-5 SFP-RAI 12 In response to SFP-RAI 2, the licensee indicated a review of plant records showed that the Boral verification testing was inconclusive for some cell locations on six BFN SFP storage modules. In order to evaluate these cell locations, a statistical analysis was performed to determine the probability that no more than one Boral plate is missing. The staff notes that if a single Boral plate is missing, then this would become part of the normal condition and should be evaluated as such. Since such a normal condition could result in a more limiting accident condition, provide the following:

a.

The locations of the cells for which the Boral verification testing was inconclusive.

b.

The statistical analysis performed to evaluate the cell locations for which the Boral verification testing was inconclusive.

c.

A technical justification for the assumption that the normal BFN SFP rack condition does not include any missing Boral plates.

d.

As part of an audit performed May 10 - 11, 2016, TVA provided draft documentation that included information to address one missing Boral panel as part of the normal condition.

In addition to submitting this information on the docket, the NRC staff requests the following information:

i.

A discussion of the applicability of the Edwin I. Hatch Nuclear Power Plant (Hatch) testing results to the BFN SFPs, more specifically addressing how the licensee has determined that the manufacturing process used to fabricate the SFP racks delivered to Hatch is the same as those delivered to BFN, and ii.

Information about any similar testing results from other sites that the licensee may be aware of.

TVA Response:

a.

During the installation of the High Density Spent Fuel Racks (HDSFRs) at BFN Units 1, 2, and 3, testing was conducted to verify the presence of Boral plates in the racks. The tests were conducted using a neutron source in conjunction with four neutron detectors.

The source was placed inside one of the tubes and the neutron signal strength in the four detectors was used to validate the presence (or absence) of the Boral plates.

As noted in the BFN response to SFP-RAI 2, testing in some cell locations in six racks (five in BFN Unit 1 and one in BFN Unit 3) proved inconclusive due to the proximity of irradiated fuel to the detectors (see Table 1 for details). Note that each unverified cell (i.e., Boral tube) location results in four unverified Boral plates because a tube has one Boral plate on each of the four walls. In the presence of gamma radiation, the detectors become saturated and their reading drops to zero, resulting in no signal and thus, an indeterminate Boral verification. This event occurred to some cell locations for six racks, as shown below:

ENCLOSURE

E-6 Table 1, Unverified Boral Plates and Rack Location Rack Size and Serial Number Unit/Rack Unverified Boral Plates Installed Tested 13x13 0002 1/4 52

<4/25/1983 6/1983 13x13 0005 1/1 52

<4/25/1983 6/1983 13x17 0021 1/9 148

<4/25/1983 6/1983 13x17 0022 1/17 104

<4/25/1983 6/1983 13x17 0023 1/13 156

<4/25/1983 6/1983 13x17 2336-6*

3/5 136 10/26/1981 10/26/1981

Rack inspection details are shown in Table 2.

In the five BFN Unit 1 racks, the exact location of the unverified cells is not currently known.

TVA is researching original construction and testing information for the racks in an attempt to determine the locations of the unverified cells.

For Rack 2336-6 in BFN Unit 3, the test record (strip chart) identified the following.

Test results for the following cells were inconclusive as indicated by the strip chart reading 0% for at least one detector and being annotated on the strip chart as being near irradiated fuel.

L1, L3, L5, L7, L9, L11, L13, L15 M2, M4, M6, M8, M10, M12, M14, M16 N1, N3, N5, N7, N9, N11, N13, N15, N17 K2, K4, K6 Cell L17 and the entire K row had readings that were approximately 1/2 of the normal readings of cells not affected by adjacent fuel. These cells are being considered inconclusive.

The following table illustrates the unverified cell locations for this particular rack.

Table 2, Unit 3 Rack 2336-6 Unverified Cell Locations A1 A3 A5 A7 A9 A11 A13 A15 A17 B2 B4 B6 B8 B10 B12 B14 B16 C1 C3 C5 C7 C9 C11 C13 C15 C17 D2 D4 D6 D8 D10 D12 D14 D16 E1 E3 E5 E7 E9 E11 E13 E15 E17 F2 F4 F6 F8 F10 F12 F14 F16 G1 G3 G5 G7 G9 G11 G13 G15 G17 H2 H4 H6 H8 H10 H12 H14 H16 J1 J3 J5 J7 J9 J11 J13 J15 J17 K2 K4 K6 K8 K10 K12 K14 K16 L1 L3 L5 L7 L9 L11 L13 L15 L17 M2 M4 M6 M8 M10 M12 M14 M16 N1 N3 N5 N7 N9 N11 N13 N15 N17

ENCLOSURE

E-7 It is anticipated that the unverified cell positions in the BFN Unit 1 racks are located in similar positions, that is, along one or more sides of the racks that bordered other racks with spent fuel, but those locations cannot be verified at this time.

b.

Because of this issue of unverified cells, the vendor at that time, GEUMCO, performed a probability analysis to determine the likelihood that there are, in fact, multiple Boral plates missing from the racks. The analysis used a binomial probability function to determine what the probability was for certain numbers of Boral plates to be missing.

This type of analysis is typical for manufacturing process errors. It should also be noted that all of the Boral plates and tubes used in fabrication of the racks were provided by the same manufacturer with the same processes and procedures. This is important to note because this further establishes the validity of the methodology and provides greater confidence that all of the Boral plates were properly installed.

In order to perform this type of an analysis, a failure rate had to be established. In this case, a failure is defined as a missing Boral plate. The failure rate was established based on prior testing history. Prior to performing the analysis, a total of 36 separate racks that contained 17,304 pieces of Boral had been tested by GEUMCO at Plant Hatch and BFN. In all cases of these inspections, the tubes were shown to contain the required Boral plates, so they were all successes in terms of probability. In order to obtain a failure rate for the probability equation, it was assumed that the very next Boral plate was missing. This equates to one failure in 17,305 tries, or a process failure rate of 5.78 x 10-5. Once the failure rate is established, the following equation describes the probability for missing Boral plates.

1 0,1,2,3 Where P = probability for a given outcome (in this case, for x missing plates) x =number of missing plates n = sample size p = process failure rate Also,

Setting the sample size equal to the number of unverified Boral plates for each rack, the following table of probabilities can be generated:

Where R = the number of missing Boral plates

ENCLOSURE

E-8 For racks with 52 unverified plates:

Number of assumed missing Plates (R)