ML033140075

Response to Second RAI Concerning the License Amendment Request to Increase the Spent Fuel Maximum Enrichment Limit with Soluble Boron Credit

ML033140075
Person / Time
Site:	Calvert Cliffs
Issue date:	11/03/2003
From:	Vanderheyden G Constellation Energy Group
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
TAC MB8896
Download: ML033140075 (4)

Text

George Vanderheyden 1650 Calvert Cliffs Parkway Vice President Lusby, Maryland 20657 Calvert Cliffs Nuclear Power Plant 410 495-4455 Constellation Generation Group, LLC 410 495-3500 Fax Constellation Energy Group November 3, 2003 U. S. Nuclear Regulatory Commission Washington, DC 20555 ATTENTION: Document Control Desk

SUBJECT:

Calvert Cliffs Nuclear Power Plant Unit No. 1; DocketNos. 50-317 Response to Second Request for Additional Information Concerning the License Amendment Request to Increase Unit I Spent Fuel Pool Maximum Enrichment Limit with Soluble Boron Credit

REFERENCES:

(a) Letter from Mr. G. S. Vissing (NRC) to Mr. P. E. Katz (CCNPP), dated July 25 2003, "Request for Additional Information, Technical Specification Change to Increase Spent Fuel Pool Maximum Enrichment Limit with Soluble Boron Credit (TAC No. MB8896)"

(b) Letter from Mr. P. E. Katz (CCNPP) to NRC Document Control Desk, dated May 1, 2003, "License Amendment Request: Increase to the Unit I Spent Fuel Pool Maximum Enrichment Limit with Soluble Boron Credit" This letter provides the information requested in Reference (a). This information supports and/or clarifies the information provided in Reference (b). This information does not affect the No Significant Hazards Consideration Determination or the Environmental Impact Review of Reference (b).

Requested Information:

1. In your letter of May 1, 2003, you proposedincreasingthe maximum enrichmentfor standardfuel assemblies to 5.0 weight percent, while te current Technical SpecifIcation of Calvert Cliffs Nuclear Power Plant (CCNPP) limits the maximum enrichment for standardfuel assemblies to 4.52 weight percent. Indicate wletler the weight of the fuel assenbliessupported by the spentfuel racks will increase as result of the enrichment. If the weight of the fuel assemblies is increased, what are the effects on the spent fuel racks and the spent fuel pool structure due to the increased weight?

CCNPP Response:

Increasing the maximum enrichment does not result in a weight increase of the fuel assemblies. The process that will be used to increase the enrichment will result in some of the heavier U-238 fuel being replaced with lighter U-235.

' OCI

Document Control Desk November 3, 2003 Page 2

2. In consideration of the possibilityfor increased loads from spent fuel racks, discuss your past operation, inspection and maintenance experience of the CCNPPspentfuel racks and spentfuel pool structures. As applicable, discuss any pool wall/bottom slab cracking, settlement and/orpool water leakages observed to date andrepairmeasurestaken to remedy then.

CCNPP Response:

Increasing the maximum enrichment will not result in increased loads.

3. What is tie maximum bulk pool temperature at afull core off-load during a refueling outage? If the temperature exceeds 150 "F, provide technicaIjustifcationsfor exceeding a gross temperature of 150 IF in accordance with the guidance in the American Concrete Institute Code 349 for long-term operation.

CCNPP Response:

As stated in the Updated Final Safety Analysis Report, Section 9.4.1, the maximum temperature with a full core off-load would be 130"F, assuming two loops of spent fuel pool cooling is in operation.

The increased enrichment does not result in the maximum temperature of the spent fuel pool exceeding the limit stated in the Updated Final Safety Analysis Report during a normal refueling outage. Assuming a more conservative bounding temperature of 155"F does not alter the design basis value of 1301F. The 155"F value denotes a worst-case short-term accident value that is not valid for long-term operation.

4. In Section 7.0, Technical Assumptions, of the license amendment request, the licensee cites that the Nuclear Regulatory Commission acknowledged commitment in Section 2.1.3.7 of the license renewal applicationfor CCNPP. In this commitment, the licensee stated it would perform an analysis on carborundum to demonstrate that it can perform its criticality controlfunction for 70years. According to Section 3.10.2.4, "Time-Limited Aging Analysis," of the Final Safetj' Evaluation Report regarding the license renewal of CCNPP Unit Nos. I and 2, the licensee's analysis was to be completed in 2000.

If the licensee proposes to credit this analysisfor its amendment request, CCNPPshould provide the analysis to support the amendment request.

CCNPP Response:

Section 2.1.3.7 of the CCNPP License Renewal Application indicates that CCNPP will perform an analysis to demonstrate that the carborundum can perform its criticality control function for a 70-year service life. The Nuclear Regulatory Commission acknowledged this commitment in NUREG-1705, Section 3.10.2.4. Therefore, it was necessary to account for the additional boron that could be lost between 40 and 70 years. In addition, previous criticality calculations have also considered a 10%

uncertainty in addition to using the worst-case B-10 loading. This uncertainty is to account for the experimental variation in boron loss rate measurement.

The original minimum loading was 0.024 gcm2 . A B-10 loading of 0.020 g/cm 2 was used in the design basis analysis to represent a 15% loss over 40 years. Linearly extrapolating this loss rate to 70 years yields (with the implicit assumption that the rate remains constant) a B-10 loading of 0.0177 g/cm 2 (0.024 - 70/40*0.15*0.024) and 0.01593 g/cm2 for the 10% uncertainty case. Note that the

Document Control Desk November 3, 2003 Page 3 carborundum test data indicates that the boron loss plateaus at gamma exposures in excess of 10"1 Rads. Thus, the use of a linear extrapolation in poison weight loss is very conservative. This effort constitutes the 70-year service life extension analysis.

S. In Attachment (1) under Background and Analysis in tie System Design section, the licensee states tat CCNPP has a coupon surveillanceprogram to test tle condition of the carborundum material. Also, the licensee indicates that as a result ofLicense Renewal, that the boron loss from the carborundum between 40 and 70 years has been analyzed. The staff requests the licensee explain how the coupon surveillanceprogram will be modified to accountfor boron depletion due to the added neutron fluence of fuel with a greater enrichment as well as the increasedplant operatinglifespan.

CCNPP Response:

Analysis has determined that the boron depletion due to the added neutron fluence of fuel with a greater enrichment will be negligible for the service life of the spent fuel pool racks (up to 70 years).

Therefore, it is not necessary to modify the coupon surveillance program to account for boron depletion. However, the coupon surveillance program was modified as follows to account for the possible degradation of the coupons during the 70 years of service in a boric acid environment.

The accelerated poison sample surveillance program initially had 12 coupons and extracted a coupon for analysis every two years. The duration was increased to eight years to account for plant-life extension, with a final withdrawal scheduled for 2037. The affected coupons are re-inserted for possible future examination.

The long-term poison sample surveillance program initially had 12 coupons and extracted a coupon for analysis every four years. The duration was increased to five years to account for plant-life extension, with a final withdrawal scheduled for 2040. The affected coupons are re-inserted for possible future examination.

Document Control Desk November 3, 2003 Page 4 Should you have questions regarding this matter, we will be pleased to discuss them with you.

Ve rUy urs, STATE OF MARYLAND

TO WIT:

COUNTY OF CALVERT I, George Vanderheyden, being duly sworn, state that I am Vice President - Calvert Cliffs Nuclear Power Plant, Inc. (CCNPP), and that I am duly authorized to execute and file this License Amendment 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 o my personal knowledge, they are based upon information provided by other CCNPP employees nor consultants. Such information has been reviewed in accordance with company practice and I I te able.

7C Subscribed and sworn before me, a Notary Pub ic in apd for the State of Maryland and County of 5;. thisP-9P day of 0?'eI A.- ,2003.

/ {) , , - n-WITNESS my Hand and Notarial Seal:

Notary Pu

-My Cornissi n Expires:

Dhte GV/DJM/bjd .--

cc: J. Petro, Esquire H. J. Miller, NRC J. E. Silberg, Esquire Resident Inspector, NRC Director, Project Directorate I-1, NRC R. I. McLean, DNR G. S. Vissing, NRC