ML051600600

Response to NRC Request for Additional Information Exemption Requested from the Requirements of 10 CFR Part 50, Paragraph 50.68(b)(1) (TAC Nos. MC5520 and MC55211

ML051600600
Person / Time
Site:	Calvert Cliffs
Issue date:	05/31/2005
From:	Montgomery B Calvert Cliffs
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
TAC MC5520, TAC MC55211
Download: ML051600600 (18)

Text

Calvert Cliffs Nuclear Power Plant Constellation Generation Group, LLC 1650 Calvert Cliffs Parkway Lusby, Maryland 20657 I9 Constellation Energy May 31, 2005 U. S. Nuclear Regulatory Commission Washington, DC 20555 ATTENTION:

SUBJECT:

Document Control Desk Calvert Cliffs Nuclear Power Plant Unit Nos. I & 2; Docket Nos. 50-317 & 50-318 Response to NRC Request for Additional Information Re: Exemption Requested from the Requirements of 10 CFR Part 50, Paragraph 50.68(b)(1) [TAC Nos. MC5520 and MC55211

REFERENCES:

(a)

Letter from Mr. R. V. Guzman (NRC) to Mr. G. Vanderheyden (CCNPP),

dated May 2, 2005, "Calvert Cliffs Nuclear Power Plant, Unit Nos. I and 2 (CCNPP I and 2) - Request for Additional Information Re: Exemption Request Concerning Plant Procedure Requirements for Handling and Storage of Fuel Assemblies in Unborated Water at the CCNPP I and 2 Spent Fuel Pool (TAC Nos. MC5520 and MC5521)

(b)

Letter from Mr. B. S. Montgomery (CCNPP) to Document Control Desk (NRC), dated December 21, 2004, Exemption Requested from the Requirements of 10 CFR Part 50, Paragraph 50.68(b)(1)

By letter dated May 2, 2005 (Reference a), you requested additional information regarding Calvert Cliffs Nuclear Power Plant, Inc.'s request for an exemption from the requirement specified in 10 CFR 50.68(b)(1) [Reference b]. Attachment (1) to this letter provides the requested information.

-OWD \\

Document Control Desk May 31, 2005 Page 2 Should you have questions regarding this matter, please contact Mr. L. S. Larragoite at (410) 495-4922.

Very truly yours, Manger - CCN P Engineering Servi STATE OF MARYLAND COUNTY OF CALVERT

TO WIT:

I, Bruce S. Montgomery, being duly sworn, state that I am Manager - Calvert Cliffs Nuclear Power Plant Engineering Services (CCNPP), and that I am duly authorized to execute and file this exemption request on behalf of CCNPP. To the best of my knowledge and belief, the statements contained in this document are true and correct. To the extent that these statements are not based on my personal knowledge, they are based upon information provided by other CCNPP employees and/or consultants. Such information has been reviewed in accordance with company practice and I believe it to be reliable.

Subscribed and sworn before me, a Notary Public in and for the State of Maryland and County of CMA~r-+

,this 3 day of On1 2005.

WITNESS my Hand and Notarial Seal:

My Commission Expires:

BSM/GT/bjd

-7 /

I o 6 Date C---

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Attachment:

(I)

Response to NRC Request for Additional Information Re: Exemption Requested from the Requirements of 10 CFR 50.68 Enclosure (1) - Drawings Enclosure (2) - Borated Water Density as a Function of Boron Loading and Temperature cc:

R. V. Guzman, NRC S. J. Collins, NRC Resident Inspector, NRC R. I. McLean, DNR

ATTACHMENT (1)

RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION RE: EXEMPTION REQUESTED FROM THE REQUIREMENTS OF 10 CFR 50.68 Calvert Cliffs Nuclear Power Plant, Inc.

May 31, 2005

ATTACHMENT (1)

RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION RE: EXEMPTION REQUESTED FROM THE REQUIREMENTS OF 10 CFR 50.68 Requested Information 1 Page 7 of your exemption request provides a description of the spent fuel pool (SFP) layout. The description does not include information about the configuration of the cask laydown area relative to the SFP. Please provide a description of the cask laydown area that adequately conveys the location, size and physical separation betveen this area and the SFP. In addition, provide a description of the SFP cooling system and supporting information that explains howt' the cask laydown area is supplied with adequate mixing and cooling. Please include drawings that complenmentyour description.

Calvert Cliffs Response Enclosure (1) contains the drawings referenced in this response. The cask laydown area lies on the southern edge of the Unit I SFP as is shown in BGE Drawing 13939SH0014 "Fuel Storage Rack Installation in Pool" and BGE Drawing 61706SH0001 "Auxiliary Building Spent Fuel Pool Liner Plan and Sections." The cask pit platform is detailed in BGE Drawing 84071SH0001 "Unit I Auxiliary Building Spent Fuel Cask Pit Platform." The cask pit platform is a 9' square and is at elevation 31' 6.5".

The cask laydown area is approximately 11' square. Thus, the center of a cask will be 6.5' from the nearest spent fuel storage rack. Note that no physical barrier separates the cask laydown area from the SFP storage racks.

The SFP cooling system is a closed loop system consisting of two heat exchangers, a filter, a demineralizer, two pumps, valves, and instrumentation. The normal configuration for the cooling system is one pump/one cooler loop in operation on each half of the SFP. The purity and clarity of the water is maintained by passing a portion of the flow through the purification system. The purification system consists of a filter to remove insoluble particulates and a demineralizer to remove soluble ions. Ten skimmers are provided in the SFPs to remove accumulated dust and debris from the surface of the water.

A schematic of the SFP cooling system is shown on BGE Drawing 60716SH0001 "SFP Cooling, Pool Fill and Drain Systems."

Water is drawn-out of the SFP by the suction action of the pump. It is drawn through two pipes (on the east wall of the Unit I SFP) which later join into one (BGE Drawing 61707SH0002 "Auxiliary Building SFP Liner Sections and Details"). If the pool level is low, a third suction line takes suction at a point below the fuel transfer tube elevation (on the south wall of the Unit I SFP), but this line is normally kept shut. The water is cooled and purified and re-enters the SFP via the inlet header, which is located on the west wall of the Unit I SFP (BGE Drawing 61707SH0002 "Auxiliary Building SFP Liner Sections and Details"). Note that all of the above inlet and outlet penetrations are at elevation 65' 11" to preclude inadvertent draindown.

Spent fuel assemblies loaded into the Independent Spent Fuel Storage Installation (ISFSI) are decayed for a long period of time, such that their heat generation rate is less than 660 watts/assembly (ISFSI Technical Specification [TS] 3.1.1). Assuming a typical loading cycle of 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, an initial 90'F SFP temperature, and a SFP water level at the lower alarm limit of 66.5', the maximum temperature increase of the water within and directly above the cask would be only 121F, conservatively assuming no lateral temperature flow and no heatup of the cask or internals. (See BGE Drawing 84012SH0001 "NUHOMS 24P ISFSI DSC Shell Assembly" and BGE Drawing 84025SH0001 "NUHOMS 24P ISFSI Onsite Transfer Cask Inner and Outer Shell Assembly" for dimensions.)

Thus, cooling of the cask laydown area during loading/unloading operation is not a concern.

I

ATTACHMENT (1)

RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION RE: EXEMPTION REQUESTED FROM THE REQUIREMENTS OF 10 CFR 50.68 Requested Information 2 Page 7 of your exemption request indicates that there is a slot in the dividing wall that has removable gates, which allow movement offuel assemblies behveen the tivo halves of the pool. Please provide the size and location of this gate as well as' its configuration (open or closed) whenever the dry storage canister (DSC) [dry shielded canister] is in the SFP.

Calvert Cliffs Response The Calvert Cliffs Nuclear Power Plant Units 1 and 2 SFP is a large rectangular structure located in the Auxiliary Building between the two Containment structures. Borated water fills the SFP and completely covers the spent fuel assemblies. The SFP is constructed of 6' of reinforced concrete and is lined with a 3/16" stainless steel plate, which serves as a leakage barrier. A 3.5' wall divides the SFP, with the north half being associated with Unit 1 and the south half associated with Unit 2. A slot in the dividing wall has removable gates, which allow movement of fuel assemblies between the two halves of the pool.

The dimensions of the removable gate are 1" x 2'-9" x 24'-1.25" (BGE Drawing 63595SH0001 "Auxiliary Building Unit 2 SFP Bulkhead Gate Structural Steel Details"). The bottom of the slot is at elevation 45'-10", while the top of the SFP racks are at 45'-2". Per BGE Drawing 63706SH0001 "Auxiliary Building Restraint for Cask in SFP," the slot centerline lies on the centerline of the Units 1 and 2 Containments. The approximate weight of the SFP bulkhead gate is 3300 lbs.

Insertion and removal of the bulkhead gate is governed by procedure. The bulkhead gate is normally stored in the Unit 1 SFP on the west side of the south wall. To support the dilution and criticality evaluations described in our exemption request (Reference 1), we will revise our fuel handling procedure to include an initial condition that requires the slot between the two pools to be open and the gate to be stored in its proper storage location, when a DSC is present in the Unit 1 SFP.

Reauested Information 3 On Page 9 ofyour exemption request it is stated:

Where stratification has occurred (Robinson 2 - December 20, 1988 and San Onofre I -

January 23, 1989). it was observed that the diluted waterfloated on top of the more highly borated water.

This suggests that if stratffcation does occur, the water with the higher boron concentration will tend to be in the lower level of the SFP where thefuel assemblies are located While reviewing previous similar exemptions for other plants (e.g. Sequoyah exemption request dated February 20, 2002 (Agency Documents Access and Management System, Accession No. ML040550203),

the Nuclear Regulatory Commission staff evaluated boron dilution analyses which assume that addition of cold water directly to the cask pit, which is denser than the warm borated pool wvater, could fill the bottom of the cask pit with water having a low boron concentration.

Please provide specific information that demonstrates that, if a direct dilution with cold *vater to the cask laydown area at CCNPP S SFP occurs, it would be expected that the water with the higher boron concentration would tend to remain in the lower level of the cask laydown area, where the fiel assemblies are located, thereby minimizing the possibility of localized boron dilution.

2 A

ATTACHMENT (1)

RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION RE: EXEMPTION REQUESTED FROM THE REQUIREMENTS OF 10 CFR 50.68 Calvert Cliffs Response To calculate the vertical thermal stratification stability of a cold liquid being placed above a warm borated liquid, the following inputs were utilized:

• The minimum required soluble boron concentration is 2450 ppm for the loading and unloading of the NUHOMS 32P DSCs in the SFP (Reference 1).

• The SFP temperature averages between 850F-90'F. A SFP initial temperature of 901F will be assumed in this analysis.

• Based on the setpoint file limits, the minimum temperature of the water in the tank farm that could be added to the pool during a dilution event is 407F. A tank farm temperature of 351F will be assumed in this analysis.

• Curves of fluid density and specific gravity vs boric acid loading as a function of temperature are included in Enclosure (2). At a SFP temperature of 901F, the following algorithm applies p = 0.995 + 0.0035*w(H3BO3) = 0.995 + 0.0200

• w(B) where w(H3BO3) is the weight percent of boric acid in solution, w(B) is the weight percent boron in solution, and p is the solution density at the specified conditions in gm/cc. Thus at 2450 ppm, p is 0.9999 gm/cc and the specific gravity (SG) is 1.005.

Thus

• The density of SFP water borated to 2450 ppm at 90TF can be calculated to be p(90'F-2450 ppm) = 1.005/(0.01610 ft3/lbm) = 62.4224 Ibm/ft3.

where 0.01610 ft3/lbm is the specific volume of water at 14.696 psia and 90TF and 1.005 is the specific gravity of water borated to 2450 ppm.

• The density of unborated cold water at 351F inserted atop the SFP is p(350F-0 ppm) = 1.0000/(0.01602 ft3/lbm) = 62.4220 Ibm/ft3.

where 0.01602 ft3/lbm is the specific volume of water at 14.696 psia and 351F.

Thus in the conservative scenario where cold water of 351F is laid atop warm water at 901F and at 2450 ppm soluble boron, the liquids are of approximately the same density. Thus the cold water will not sink en masse below the warm borated water and cause a criticality event. The cold water will either gradually equilibrate and mix with the SFP water or will flow out of the SFP via the overflow drains.

To determine equilibration rates between bodies of water at different temperatures, a GOTHIC model was constructed, assuming a warm unborated SFP at 130'F below a I foot layer of unborated cold water at 401F. The results indicate that temperature equilibration occurs within 120 seconds and that the cold water does not reach the top of the active fuel region before equilibration.

Note that the above analyses assume that the cold unborated water is gently laid atop the SFP. If the cold water is thrust into the SFP via a fire hose, the momentum will carry it down into the pool. This type of incomplete boron mixing is denoted as a ribbon effect, where a channel of unborated water bores its way to a SFP location. Assuming that the SFP cooling and purification systems are not in operation, an analysis using turbulent jet and diffusion theory can be performed to determine the extent of any ribbon effect. Per Combustion Engineering, Inc. CE NPSD-985-P Revision 1, "Crediting Soluble Boron in 3

ATTACHMENT (1)

RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION RE: EXEMPTION REQUESTED FROM THE REQUIREMENTS OF 10 CFR 50.68 LWVR SFPs" (Reference 2), the change in concentration per length of the jet flow can be estimated via the algorithm Q/Q0 = 0.42* z/d, where Q0 is the volumetric flow rate at the nozzle discharge, d is the nozzle diameter, and Q is the volumetric flow rate at a distance z from the nozzle along the axis of symmetry.

The volumetric flow will increase along the jet flow path, due to entrainment of the bulk liquid as the jet flow diameter increases. The ratio of volumetric flow rate to the initial volumetric flow rate determines the amount of bulk fluid entrained in the jet flow and thus is representative of the boron concentration along the flow path C

• Q = Co * (Q - Qo)

Q/Qo Co/(Co - C) = 0.42

• z / d C = Co * (I - d / (0.42

• z))

The cask pit platform is at elevation 31' 6.5" (BGE Drawing 84071SH0001 "Unit I Auxiliary Building Spent Fuel Cask Pit Platform"). The transfer cask is 15.07' in length (BGE Drawing 84025SH0001, "NUHOMS 24P ISFSI Onsite Transfer Cask Inner and Outer Shell Assembly"). The top of the SFP water is assumed to be at the lower alarm limit of 66.5' per the setpoint file. Thus the distance from the top of the pool to the top transfer cask is 19.89'. For a CO of 2450 ppm and a 3" diameter fire hose, C will reach 2377 ppm before entering the transfer cask. Thus the assemblies in the DSC will remain subcritical by a large margin.

Requested Information 4 On Page 14 ofyour exemption request, it is stated that the operators perform comprehensive training and testing on the alarm manuals during initial qualification and re-qualification every 2 years. Please state whether this training will provide awareness to the operators of the additional requirements for higher boron concentrations that apply during loading, unloading and handling operations using the NUHOMS-32PO DSC.

Calvert Cliffs Response The higher boron concentration that applies during loading, unloading, and handling operations using the NUHOMS-32P DSC is an ISFSI Technical Specification limit.

All appropriate alarm manual procedures will be revised to verify that SFP boron concentration is in compliance with the new Technical Specification limit prior to loading a NUHOMSt-32P DSC. Operators involved in the loading of a NUHOMS"-32P DSC will receive training on the revised alarm manual procedures.

REFERENCES

1. Letter from Mr. B. S. Montgomery (CCNPP) to Document Control Desk (NRC), dated December 21, 2004, Exemption Requested from the Requirements of 10 CFR Part 50, Paragraph 50.68(b)(1)

2. CE NPSD-985-P Revision 1, "Crediting Soluble Boron in LWR SFPs" 4

Enclosure (1)

Drawings BGE Drawing 13939SH0014 BGE Drawing 61706SH0001 BGE Drawing 84071SH0001 BGE Drawing 60716SH0001 BGE Drawing 61707SH0002 BGE Drawing 84012SH0001 BGE Drawing 84025SH0001 BGE Drawing 63595SH0001 BGE Drawing 63706SH0001 Calvert Cliffs Nuclear Power Plant, Inc.

May31,2005

Enclosure (2)

Borated Water Density as a Function of Boron Loading and Temperature Density of Boric Acid Solutions Page A-3 of A-4 Specific Gravity of Boric Acid Solutions Page A-4 of A-4 Calvert Cliffs Nuclear Power Plant, Inc.

May 31, 2005

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