ML20217F046

Forwards Response to RAI Re North Anna ISFSI for Concrete Pad Design,Transporter Design,Cask Loading Operations & Record Keeping Requirements

ML20217F046
Person / Time
Site:	North Anna
Issue date:	04/23/1998
From:	Ohanlon J VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	Paperiello C NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS)
References
98-112, TAC-L22113, NUDOCS 9804280037
Download: ML20217F046 (8)

Text

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eis VIR(3INI A MIECTRIC AND POWER C(nWANY Ricinunni>, % R(;INI A D2(,I l

April 23, 1998 Mr. Carl J. Paperiello, Director Serial No.98-112 l

Office of Nuclear Material Saisty and Safeguards NL&OS/TJS RO l

U. S. Nuclear Regulatory Coic. mission Docket No. 72-16 Washington, D. C. 20555 Gentlemen:

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VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA INDEPENDENT SPENT FUEL STORAGE INSTALLATION (ISFSl)

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION (TAC NO. L22113) l Virginia Electric and Power Company (Virginia Power) submitted an application for the l

review and approval of a site-specific license for an independent spent fuel storage installation (ISFSI) at North Anna Power Station on May 9,1995 (Serial No.95-195).

The NRC submitted a Request for Additional Information to Virginia Power on February j

13,1998 concerning concrete pad design, transporter design, cask loading cperations l

and record keeping requirements. Attached is our response to the Request for Additional Information.

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Please contact us if you have any questions or require addit!onalinformation.

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Very truly yours, i

h (K

. O'Hanlon Se r Vice President - Nuclear

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Attachment j

Commitments made by this letter:

1.

Movement of casks ready for transport will be limited by procedure to address weather-related contamination considerations until a NAPS crane enclosure can

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be constructed by Virginia Power.

, OW 9804280037 980423 PDR ADOCK 0500o338 Y

PDR

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i cc:, Mr. Jr W. Shea L

Office of Nuclear Material Safety and Safeguards U. S. Nuclear Regulatory Commission, Mail Stop 14-H-22 Washington, D. C. 20555 United States Nuclear Regulatory Commission Attention: Document Control Desk Washington, D. C. 20555-0001

.,v Mr. M. J. Morgan NRC Senior Resident Inspector North Anna Power Station I

ATTACHMENT 1 1

Response To A Request For Additional Information Design Features of the Nortn Anna ISFSI and Transporter, Cas'.oading Operations and Record Keeping Requirements 1.0 NORTH ANNA ISFSI DESIGN CRITERIA 1.1 NRC BACKGROUND CONIMENT Virginia Power proposes to use the TN-32 as its storage cask at the North Anna ISFSI.

- The TN-32 Topical Safety Analysis Report (TSAR) tip-over and cask bottom end drop analyses assumed the following bounding conditions for the concrete storage pad: a) the pad is not more than three feet thick, b) the concrete strength is not greater than 4000 psi, and c) the soil modulus of elasticity is not greater than 40 ksi.

Section 5 of the North Anna SAR Technical Specifications lists the concrete storage pad design thickness as two feet " nominal." Additionally, Chapter 4 of the SAR states that the concrete pad shall be designed with a minimum concrete strength of 3000 psi, however, no maximum strength is given. The concrete pad parameters proposed by Virginia Power do not fully capture the bounding conditions assumed in the TN-32 TSAR. Therefore, the staff considers the proposed concrete pad design criteria inadequate to ensure that the TN-32 could meet the ISFSI design criteria listed in Table 3.4-1 that states the " cask is capable of tipping over and rolling without compromising i

the SSSC integrity and without physical damage to fuel or loss of suberiticality."

1.2 NRC REQUEST 1.2.1 Clarify the concrete pad design criteria used for the North Anna ISFSI and justify any deviation from the bounding concrete pad design criteria considered in TN-32 TSAR. If the North Anna design criteria are different from the TN-32 TSAR design criteria, demonstrate that the TN-32 will maintain its integrity during a tip-over or end drop event at the North Anna ISFSI.

1.2.2 Provide a proposed design criteria that establishes clearer, more comprehensive criteria for the North Anna ISFSI.

1.3 VIRGINIA POWER RESPONSE Certain as-built parameters of the North Anna ISFSI concrete storage pad differ from the parameters listed in the TN-32 Dry Storage Cask Topical Safety Analysis Report.

The following table shows some of the pad parameters that were listed in the TSAR versus the as-built pad parameters reported for the North Anna Power Station ISFSI concrete storage pad:

1; Soil Modulus Concrete Slab Slab Clear 2

of Elasticity,

'cmpressive Thickness, Reinforcing Concrete

Strength, Steel,.

Cover, E,

f, h

A, c

I NAPSISFSI

1. 10 @ 12",

2 in., (top As-built 30,000 psi 5,060 psi 24 in.

each way, bars),

Parameters top -&

3 in.,

(Reported) bottom (bottom bars)

USNRC As As Parameters 40,000 psi 4,000 psi 36 in.

Required Required

. (SER 3.3.3) for Pad for Rebar Strength Protection TSAR

1. 11 @ 12",

2 in., (top &

Parameters.

32,600 psi 3,000 psi 36 in.

each way, bottom (App.3A) top &

bars) bottom Design criteria for the ISFSI concrete storage pad requires that the pad be sufficiently robust to withstand the maximum loads associated with all cask load conditions, yet r

" soft" enough to limit the deceleration of the cask during design accident cases, so as not to create an overstress in the cask or basket intemais. The NRC has concluded that TN-32 cask confinement and spent fuel retrievability will be assured if the following parameters of the concrete storage pad are satisfied: 1) h 5 36 inches,2) f,5 4,000 psi, and 3) E,5 40,000 psi.

Pad hardness will vary directly with changes in pad parameters E, f, h, and A, and e

vary inversely with concrete cover, c. A comparison between the reported NAPS as-built and the listed NRC SER pad parameters indicates that the increase in concrete compressive strength, f, from 4,000 psi to 5060 psi, is the only as-built parameter that.

e supports an increased pad hardness above NRC identified criteria. All other as-built pad parameters tend to decrease or " soften" the pad hardness, while still providing acceptable strength. The relative rates at which these as-built pad parameters affect strength are easily' determined, via design code equations and strength of materials techniques. The relative rates at which these parameters affect pad hardness presents somewhat of a more complex problem.

Concrete slab flexural rigidity can be expressed by the following equations:

D, = E, h3 / [12(1-u )]; where E, = 57,000(f )u2, as defined by ACI 349-85 2

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In these equations, slab rigidity varies as a function of (f )'" and h. In the NAPS ISFSI e

as-built ccncrete storage pad, increased (f, ) accounts for a (5,060 psi / 4,000 psi)'* =

1.125, or a 12.5% increase in rigidity; whereas decreased (h) accounts for a (24" / 36")

= 0.296, or a 70.4% reduction in rigidity. By this example alone, it can be reasoned that reduced pad thickness offsets the increased pad rigidity attributed to the rise in concrete compressive strength, thereby creating a net reduction in pad flexural rigidity, hence pad hardness.

Assuming all other NAPS ISFSI concrete storage pad parameters remain unchanged, cask deceleration values, listed in Section 3.3.3, " Accident Conditions," of the Safety Evaluation Report were appropriately scaled down to account for the " softer" net effect of the reported as-built pad parameters. A summary of the new estimated cask deceleration values are listed below:

Accident Condition New Design "G" Value SER "G" Value 50 g VOK Cask Bottom End Drop 35 g

=

63 g VOK Cask Side Drop - Cask Body 41 g

=

i 88 g VOK Cask Side Drop -Top of Basket 58 g

=

34 g 52 g 4OK Cask Side Drop - 90 Basket X-Sect.

=

Therefore, it is concluded that the NAPS as-built ISFSI concrete storage pad is within its design basis with respect to the TN-32 cask design deceleration values.

2.0 TRANSPORTER i

2.1 NRC BACKGROUND COMMENT The TN-32 storage cask has been evaluated for an 18-inch drop onto a concrete pad l

as described in 1.1 above. The IJorth Anna SAR Technical Specifications limit the cask l

lift height to 18 inches and Section 4.3.3 of the SAR states that the transporter is designed to limit SSSC lift height to less than 15 inches, however there is no discussion of how this limit is maintained.

2.2 NRC REQUEST Provide additional detail on the transporter design features that limit the cask lifting 1

height to 15 inches.

2.3 VIRGINIA POWER RESPONSE l

The transporter uses hydraulic jacking towers to lift the storage cask. Control of the i

lifting height is a design feature of the towers. These towers have internal mechanical j

stops that prevent liftir.g of the TN-32 cask more than 15 inches off the grou.d. The towers must be disassembled to change the position of these mechanical stops.

3.0 CONTAMINATION FROM CASK LOADING OPERATIONS 3.1 NRC BACKGROUND COMMENT Section 6 of the SAR discusses the control of contamination for various aspects of the cask loading and unloading operations. No discussion is provided to address any contamination on the cask crane lifting equipment.

3.2 NRC REQUEST Provide a discussion of the design features and/or operational practices that will prevent the potential weather driven spread of contamination from the cask crane lifting equipment as it traverses from the spent fuel pool to outside the Decontamination Building where the loaded cask is placed prior to transporting to the ISFSI pad.

3.3 VIRGINIA POWER RESPONSE As a loaded cask is removed from the spent fuel pool, water sprays are used to reduce the surface contamination from the cack crane, cask lift yoke and cask. After removal from the pool, the cask is moved to the testing and preparation bay in the Decontamination Building, which is in a covered area next to the Fuel Building. After placement of the cask in the bay, the crane book, exterior portions of the crane block and the lift yoke are decontaminated. Some parts of the cask crane, such as the cables, cannot be further decontaminated. When the cask is ready for transport to the ISFSI, it is lifted from the bay and moved outside the covered area and lowered to the ground.

In the long term, to prevent the weather-driven spread of contamination from the cask lifting equipment, Virginia Power intends to erect an enclosure over the cask crane structure.

Until a crane enclosure is in place, the movement of casks ready for transport will be limited by procedure to times when weether will not be a factor in the spread of contamination. These limitations will include restrictions addressing precipitation and wind velocity.

4.0 RECORD KEEPING REQUIREMENTS i

4.1 NRC BACKGROUND COMMENT i

Section 9.4.2 of the North Anna SAR states that records will be maintained on the l

identity of each fuel assembly, in accordance with 10 CFR 72.72. The requirements for keeping records in duplicate and for a minimum period after the spent fuel is transferred from the !SFSI, as specified in 10 CFR 72.72, are not addressed in the SAR. The record keeping requirements of 72.72 (b) and (c) are also not addressed. Additionally, the record keeping requirements of 10 CFR 72.30 (d) are not addressed.

4 4.2 NRC REQUEST Provide additional description of the methods used to comply with the record keeping requirements of 10 CFR 72.72 (a),72.72 (b),72.72 (c),72.72 (d) and 72.30 (d).

1 4.3 VIRGINIA POWER RESPONSE 72.30(d)

Records for decommissioning of the ISFSI that will be retained under 10 CFR 72.30 (d) include the following:

1. Records of spills or other unusual occurrences involving the spread of contamination in and around the ISFSI

2. As-built drawings and modifications of structures and equipment at the ISFSI

3. A list contained in a single document and updated no less than every two years of a) all areas designated and formerly designated as restricted areas as defined by 10 CFR 20.1003, and b) all areas outside of restricted areas that require documentation under item 1 of this response

4. Records of the cost estimate performed for the decommissioning funding plan and the funding method used for assuring funds Records Management will maintain these records until the site is released for unrestricted use.

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72.12 (a) <

l Records on the spent fuel stored at the ISFSI that will be retained under 10 CFR 72.72

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(a) include the following:

1.) Fuel manufacturer 2.) Date of delivery to the Station

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3.) Reactor exposure history 4.) Burnup 5.) Calculated special nuclear material content 6.) Inventory control number 7.) Pertinent data on discharge and storage at the reactor, transfer to the ISFSI, j

storage at the ISFSI and disposal 8.) Other information needed to verify compliance with ISFSI Technical Specifications These records will be maintained by Records Management for the period that the spent fuel is stored at the NAPS ISFSI plus five years after transfer.

72.72 (b)

A record of the current physical inventory of spent fuel at the ISFSI required by 10 CFR 72.72 (b) will be retained by Records Management until the ISFSI license is terminated

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. by the Commission.

72.72 (c).

The current material control and accounting procedures required by 10 CFR 72.72 (c) will be retained by Records Management until the ISFSI license is terminated by the Commission.

72.72 (d)

Records of spent fuel in storage will be kept in duplicate as required by 10 CFR 72.72 l

' (d). One copy will be stored at the North Anna Power Station. The second copy will be stored at the innsbrook Technical Center west of Richmond. Records of spent fuel transferred out of the ISFSI will be preserved for a period of five years after the date of transfer.

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