ML20116F823

Application for Amends to Licenses DPR-53 & DPR-69,allowing Use of Blind Flanges During Modes 1-4 in Plant Containment Purge Sys

ML20116F823
Person / Time
Site:	Calvert Cliffs
Issue date:	08/01/1996
From:	Cruse C BALTIMORE GAS & ELECTRIC CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20116F826	List: ML20116F823 ML20116F828
References
NUDOCS 9608070167
Download: ML20116F823 (9)

Text

_ _ _ _ _ _ _ _ _ _ _ .

i,O j l

CarnIs 11. Curse Baltimore Gas and Electric Company Vice President Calvert Cliffs Nuclear Power Plant Nuclear Energy 1650 Calvert Cliffs Parkway Lusby, Maryland 20657 410 495-4455 August 1,1996 U. S. Nuclear Regulatory Commission Washington, DC 20555 ATTENTION: Document Control Desk

SUBJECT:

Calvert Cliffs Nuclear Power Plant Unit Nos.1 & 2; Docket Nos. 50-317 & 50-318 License Amendment Request: Use of Blind Flanges in Place of the Containment Purge Valves During Operation Pursuant to 10 CFR 50.90, the Baltimore Gas and Electric Company hereby requests an Amendment to Operating License Nos. DPR-53 and DPR-69 to allow use of blind flanges during Modes 1-4 in the Calvert Cliffs Units 1 and 2 Containment Purge Systems. These blind flanges will establish containment integrity in Mode 5, prior to entering Mode 4, and maintain it in Modes 1-4, functions presently served by valves. Use of the Hanges will increase the level of safety since the design and method ofinstalling the flanges nakes a more reliable seal against the post-accident pressure in containment. Testing and maintenance of the valves when entering a shutdown condition (Modes 5 and 6) has caused some delays in outage schedules. Use of the blind Danges will help alleviate this problem. See Attachment (1) for a complete discussion. The affected Technical Specifications are 4.6.1.1.d,4.6.1.2.e,4.6.1.2.f,3/4.6.1.7, 3/4.6.4.l(footnote),4.6.4.1.2.b, and 4.9.4.b. Also affected are Technical Speci0 cation Bases 3/4.6.1.7 and Table 3.3-3. They are shown on the markups in Attachments (3) and (4). The final Technical Specification pages will be renumbered to accommodate added and/or deleted pages.

We have coraidered the possibility of significant hazards associated with this change and have determined that there are none (see Attachment 2 for a complete discussion). We have also determined that operation with the proposed amendment would not result in any significant change in the types, or significant increases in the amounts, of any efnuents that may be released offsite, nor would it result in any significant increase in individual or cumulative occupational radiation exposure. Therefore, the proposed amendment is eligible for categorical exclusion as set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR Sl.22(b), no environmental impact statement or environmental assessment is needed in connection with the approval of the proposed amendment.

These proposed changes to the Technical Specifications and our determination of significant hazards have been reviewed by our Plant Operations Safety Review Committee and Offsite Safety Review Committee, and they have concluded that implementation of these changes will not result in an undue risk to the health and safety of the public.

l 9608070167 960801 PDR P ADOCK 05000317 PDR g}

Document Control Deck August 1,1996 Page 2 This proposed amendment is dependent on the completion of a modification of the containment purge system, which can only be done during an outage. Therefore, this change is requested to be approved and issued by April 1,1997, with implementation for Unit 2 during the 1997 refueling outage. Once the modification is begun, we will not be able to return to power until the amendment is implemented. We are also requesting delayed implementation to the 1998 refueling outage for the Unit 1 Technical Specifications as the modification to that unit will not be done until that time.

Should you have questions regarding this matter, we will be pleased to discuss them with you.

Very truly yours, 4

/

STATE OF MARYLAND  :

TO WIT:

COUNTY OF CALVERT  :

I hereby certify that on the day of 4 09_5 .19 , before me, the subscriber, a Notary Public of the State of Maryland in and for d Cn/ved Counk/ , personally appeared Charles 11. Cruse, being duly sworn, and states that he is Vice Presidedt of the Baltimore Gas and Electric Company, a corporation of the State of Maryland; that he provides the foregoing response for the purposes therein set forth; that the statements made are true and correct to the best of his knowledge, information, and belief; and that he was authorized to provide the response on behalf of said Corporation.

WITNESS my IIand and Notarial Seal: 2 No dL ,

Notary Public I My Commission Expires: c tec2 tcy 2 /$

D t'9e CllC/EMT/ dim l l

Attachments: (1) Background and Safety Analysis i (2) Determination of Significant 11azards l (3) Unit 1 Technical Specification Marked-Up Pages (4) Unit 2 Technical Specification Marked-Up Pages (5) Containment Purge System Illustration (Present Arrangement)

(6) Containment Purge System Illustration (Modified Arrangement) cc: D. A. Brune, Esquire T. T. Martin, NRC J. E. Silberg, Esquire Resident inspector, NRC Director, Project Directorate 1-1, NRC R.1. McLean, DNR A. W. Dromerick, NRC J. II. Walter, PSC

,. o, ATTACHMENT (1)

{

i h

l BACKGROUND AND SAFETY ANALYSIS l

l I

l l

l l

l

(

i d

l Baltimore Gas and Electric Company ,

Calvert Cliffs Nuclear Power Plant August 1,1996

e RfACHMENT (1)

HACKGROUND AND SAFETY ANALYSIS The purpose of the Containment Purge System is to provide ventilation of the containment while the plant is in a shutdown condition (Modes 5 and 6). The system consists of air supply and exhaust piping penetrating the containment wall, both of which are 48 inches in diameter (Attachment 5). The supply side admits outside air into the containment, and the exhaust side takes suction from the containment and discharges to the plant ventilation system. There is no physical connection between the supply and exhaust. In each penetration are two in-line valves (one on the outside and one on the inside of the containment wall) which are shut to provide containment integrity in Modes 1-4. Technical Specification 3.6.1.7 requires not only that the containment purge supply and exhaust valves are shut in Modes 1-4, but that the air to the air operators be isolated and the air supply solenoid valves de-energized to ensure that the penetration valves remain closed. In Modes 5 and 6, the valve operators can be unisolated and the valves opened to provide ventilation. In Mode 5, the valves can be shut manually from the Control Room. In Mode 6, the valves are capable of being shut automatically on a Containment Radiation Signal, as well as manually. As explained later, only one of each pair of valves is credited for Containment Building closure.

The purpose of maintaining containment integrity in Modes 1-4 is to contain radioactive material inside the containment in the event of an accident. The controlling accident is a loss-of-coolant accident which will produce a pressure increase in containment. The valves must maintain a tight seal to prevent the i escape of radioactive material until containment pressure can be reduced. In the past, we have l encountered leakage problems when pressure testing the valve seals in accordance with Technical Specification 4.6.1.2.e. Historically, the problems have not indicated a failure of containment integrity, j as leakage has only occurred in one of the two valves at any one time. The leakage typically appears in i

one part of the seal because the valve seal tends to deform itselfin the shape of the disc when the valve is '

shut for extended periods. Since the seal adopts a set position, and there is not sufficient reseating force at the edges of the disc to reform the seal, any movement of the disc can create small openings between it and the seal. Adjustment and retesting of the seals has involved some expense and delays in completing i

outages.

Because there is difficulty in seating these valves properly, we propose using blind flanges for containment integrity, in Modes 1-4, instead of the valves. The outer valve will be removed and a blind flange will be installed on the penetration piping outside the containment in both the exhaust and supply lines (an illustration is included as Attachment 6). The blind flanges are designed in accordance with the applicable ASME Code and Standards for the Containment and Containment Purge System. The design utilizes two concentric O-rings mounted in grooves in the face of each blind flange. The blind flanges will be removed and the purge piping connected for purging the containment in Modes 5 and 6.

Installation and removal will be controlled by plant procedures and Technical Specifications.

Blind flanges, in general, are considered more capable of providing this type of pressure-retaining function than active components, such as the purge valves. Instead of being supported only along a central axis, the blind flanges will be bolted around the circumference and will not be subject to significant movement while in service. Therefore, the seals on the blind flanges will not change their position and can be expected to remain air tight throughout the operational period. Similar blind flanges are presently in use in the fuel transfer tubes and have proven reliable. The blind flanges will be pressure tested, as provided in the Technical Specifications changed by this amendment, and as required by 10 CFR Part 50, Appendix J for Type B penetrations. Both the blind flanges and the valves will be maintained in accordance with the plant maintenance program.

1

W ATTACHMENT (1)

BACKGROUND AND SAFETY ANALYSIS Containment closure for Modes 5 and 6 is defined in Generic Letter 88-17 as ". . a containment condition where at least one integral barrier to the release of radioactive material is provided." In addition, Calvert Cliffs Technical Specifications state, in Section 3/4.9, that certain containment penetrations must,"Be capable of being closed by an OPERABLE automatic containment purge valve."

(emphasis added). Single failure criteria is not assumed for the fuel handling accident analysis in Chapter 14 of the Updated Final Safety Analysis Report. Since only one barrier is required for shutdown conditions and the flanges will provide containment integrity for Modes 1-4, we plan to remove the l outside purge valve, and the associated automatic closure signal on both the supply and exhaust sides to accommodate the installation of the flanges.

i The only shutdown accident analysis which credits the purge valves is the fuel handling accident analysis. To accommodate this analysis, the existing purge valves inside containment will remain in ,

place and will continue to be available to close. The fuel handling incident will not result in a pressure I increase in the containment, so the valves are not expected to have any difficulty seating properly. We I have also evaluated a loss-of-shutdown cooling condition, which could result in a maximum containment pressure increase of approximately 12 psi. The valves will be required to be tested in Mode 5, prior to l use, to ensure they adequately seal against this pressure. Testing exnecience has shown that the valves will seal more reliably at this pressure than at full containment post-LOCA pressure.  !

l The Technical Specifications are proposed to change as follows: ,

> Table 3.3-3, Item 6 will be changed to indicate one manual switch per valve since the number of valves in each penetration will be reduced to one.

> A new surveillance,4.6.1.1.d, will verify installation and sealing of the blind flanges before entering Mode 4 following a shutdown in which the blind flanges were removed.

> The requirement for as-found testing of the valves in 4.6.1.2.e will be deleted as the valves will not serve a containment integrity function in Modes 1-4.

> Valve seal replacement required by 4.6.1.2.f will be deleted since the seals will not be relied on in Modes 1-4, and will be procedurally inspected and tested in Mode 5. i

> Technical Specification 3/4.6.1.7 will be deleted because the valves will no longer l maintain containment integrity in Modes 1-4. The basis for this specification will be deleted also.

> Specification 3/4.6.4.1 will be modified to delete the statement in the footnotes that containment purge isolation times are not applicable for Modes 1-4. This statement will not be required since Technical Specification 3/4.6.1.7 is being deleted.

> Specification 4.6.4.1.2.b will be deleted. The Containment Radiation Signal is only required during the time the purge valves are required to be operable (Table 3.3 3).

Testing the valves during the operable period (core alterations and fuel movement) is required by Technical Specification 4.9.9 and, therefore, Technical 2

AIIACIIMENT (1)

BACKGROUND AND SAFETY ANALYSIS l

Specification 4.6.4.1.2.b is not required. Specification 4.6.4.1.2.c will be renumbered ,

to4.6.4.1.2.b. I

> Finally, Surveillance 4.9.4.b will be changed to refer to Specification 4.9.9 since this specification is more descriptive of the purge valve test.

In summary, the function of the Containment Purge System will not be changed by this amendment. l Using the blind flanges in place of the existing valves will provide a more reliable seal against postulated l post-accident pressure in Modes 1-4. This change will also still allow containment purge in Modes 5 and 6 by utilizing the remaining inside purge valves to provide automatic containment closure in the event of a fuel handling accident and a reliable seal should a loss of shutdown cooling occur. This amendment represents an improvement in plant safety and should be approved.

1 1

I l

l I

l l

l l

}

3

a i

4 i

ATTACHMENT (2)

! l

! I l

I i

j i

i d

l DETERMINATION OF SIGNIFICANT HAZARDS i l I

i 1

s

)

i 1

i; I 1 i

i a

l 1

Ilattimore Gas and Electric Company Calvert Cliffs Nuclear Power Plant August 1,1996

1 ATTACIIMENT (2) l DETERMINATION OF SIGNIFICANT IIAZARDS l The proposed change has been evaluated against the standards in 10 CFR 50.92 and has been determined to not involve a significant hazards consideration in that operation of the facility in accordance with the proposed amendments:

l

1. Would not involve a significant increase in the probability or consequences of an accident previously evaluated.

The purpose of the Containment Purge System is to provide ventilation for the containment I while in a shutdown condition. Valves, which are disabled in the shut position in Modes 1-4, may be opened in Modes 5 and 6 to allow air flow, are provided in the supply and exhaust piping, and are automatically shut on a Containment Radiation Signal to prevent release of radioactive material in the event of a fuel handling incident. Manual operation is also provided.

l In Modes 1-4, the valves are kept shut to provide containment integrity to withstand a presumed increase in containment pressure in the event of a loss-of-coolant accident. The proposed change will allow blind flanges to serve in place of the purge valves in Modes 1-4 by blocking off the  ;

purge penetration on both the supply and exhaust sides. The blind flanges will provide the same l level of containment integrity previously provided by the purge valves. The revised Technical Specifications will continue to verify containment building leakage is maintained within the allowable limits by requiring the performance of a 10 CFR Part 50, Appendix J, Type B, leakage l test on the blind Ganges. The outside valve in each containment purge penetration will be removed and the inside valves will be left in place. The remaining inside valves will no longer be required to provide containment integrity in Modes 1-4. Only one of each pair of valves was l credited for containment closure (Modes 5 and 6); therefore, removing the outside valves and the associated automatic closure signals is not a modification of the required capability to close the

! penetration. The inside valves will maintain their current safety function to close containment (if needed) by closing either on a Containment Radiation Signal (Mode 6) or manually (Modes 5 and 6). The Technical Specification surveillances associated with the purge valves will be changed to reflect the proposed modification to the plant. Since the blind flanges will limit radiological releases in Modes 1-4, and the purge valves will limit radiological releases in l Modes 5 and 6, the proposed change will not increase the consequences of an accident previously evaluated.

The Containment Purge System is not an accident initiator but acts to limit the consequences of accidents. The system will provide containment isolation in Modes 1-4 as before, and the inside valves will still be available to close in Modes 5 and 6. Therefore, the proposed change does not l

increase the probability of an accident previously evaluated.

As stated above, the proposed changes do not involve a significant increase in the probability or consequences of an accident previously evaluated.

2. Would not create the possibility of a new or different type of accident from any accident previously evaluated This requested change does not involve a significant alteration of the operation of the plant, and no new accident initiation mechanism is created by the modification. Four purge valves per unit currently provide containment closure in Modes 5 and 6. The outside valve in the supply and the exhaust lines will be removed to allow for installation of a blind flange in each line. The l

1 1

ATTACIISIENT (2)

DETERMINATION OF SIGNIFICANT IIAZARDS remaining supply and exhaust valves inside containment will continue to provide containment closure. The function currently performed by the four purge valves in Modes 1,2,3 and 4 will l be performed by the blind flanges. Other, similar, blind flanges have been in service in the plant l for a number of years, and have proven reliable. The Technical Specification surveillances associated with the testing of the purge valves and flanges will be changed to reflect the proposed modification to the plant. Therefore, this change does not create the possibility of a new or different type of accident from any accident previously evaluated.

3. Would not invoh e a significant reduction in the margin ofsafety.

The valves in the Containment Purge System currently provide containment integrity during Modes 1,2,3 and 4, and containment closure during Modes 5 and 6. The function currently performed by the purge valves in Modes 1,2,3 and 4 will be performed by the blind flanges.

Because of their design and mounting method, the blind flanges will perform the containment integrity function as well as, or better than, the purge valves. In Modes 1-4, the double o-rings in the blind flanges will provide single-failure protection similar to the other existing Type B penetrations. The established allowable containment building leakage rate will be maintained by the implementation of a requirement to perform 10 CFR Part 50, Appendix J, Type B, leakage rate on the installed blind flanges. The outside valve in each purge containment penetration will be removed. Single failure is not assumed in the fuel handling accident analysis, therefore, removing the outside valves and their Containment Radiation Signal channels is not a modification of the renuired capability to close the penetration. The remaining inside valves will continue to provide automatic and manual containment closure in Mode 6 to mitigate the effects of a fuel handling accident. The Technical Specification surveillances associated with purge valve testing will be changed to reflect the proposed modification to the plant. Therefore, this change does not involve a significant reduction in the margin of safety.

i l

I 1

l l

2