ML18066A856
| ML18066A856 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 01/27/1997 |
| From: | Bordine T CAROLINA POWER & LIGHT CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML18066A857 | List: |
| References | |
| GL-96-06, GL-96-6, NUDOCS 9702030038 | |
| Download: ML18066A856 (10) | |
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- r consumers Power l'OWERINli MIUllliAN-S l'ROlillEJS Palisades Nuclear Plant: 27780 Blue Star Memorial Highway, Covert, Ml 49043 January 27, 1997 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555 DOCKET 50-255 - LICENSE DPR PALISADES PLANT Thomas C. Bordine Manager, Licensing 120-DAY RESPONSE TO GL 96-06, ASSURANCE OF EQUIPMENT OPERABILITY AND CONTAINMENT INTEGRITY DURING DESIGN BASIS ACCIDENT CONDITIONS On September 30, 1996, the NRC issued Generic Letter (GL) 96-06, which requested a summary report of actions taken within 120 days. This letter provides that report. provides specific responses to the information requested by GL 96-06. In addition, Attachment 2 provides an operability assessment for transient conditions and provides an operability evaluation for two-phase flow conditions.
Based on the analyses performed and corrective actions already taken, Palisades has no concerns for operability of containment air coolers or other piping systems inside containment. Additional analyses are planned to assess whether further actions will be warranted.
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SUMMARY
OF COMMITMENTS This letter contains one new commitment and no revisions to existing commitments.
The commitment is:
2 Compliance with FSAR piping design criteria for the CAC discharge piping will be verified prior to the completion of the 1998 refueling outage.
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Thomas C. Berdine Manager, Licensing CC Administrator, Region Ill, USNRC Project Manager, NRR, USNRC NR~ Resident Inspector - Palisades 3 Attachments
CONSUMERS POWER COMPANY To the best of my knowledge, the contents of this 120-day response to Generic Letter 96-06 are truthful and complete.
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Thomas C. Bordine Manager, Licensing Sworn and subscribed to before me this o7 7 ~ day of M 1997.
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Alora M. Davis, Notary Public Berrien County, Michigan (Acting in Van Buren County, Michigan)
My commission expires August 26, 1999
ATTACHMENT 1 CONSUMERS POWER COMPANY PALISADES PLANT DOCKET 50-255 120-DA Y RESPONSE TO GL 96-06, ASSURANCE OF EQUIPMENT OPERABILITY AND CONTAINMENT INTEGRITY DURING DESIGN BASIS ACCIDENT CONDITIONS 4 Pages
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120-DAY RESPONSE TO GL 96-06. ASSURANCE OF EQUIPMENT OPERABILITY AND CONTAINMENT INTEGRITY DURING DESIGN BASIS ACCIDENT CONDITIONS NRC REQUESTED ACTION(S)
Addressees are requested to determine:
(1) if containment air cooler cooling water systems are susceptible to either waterhammer or.two-phase flow conditions during postulated accident conditions; (2) if piping systems that penetrate the containment are susceptible to thermal expansion of fluid so that overpressurization of piping could occur.
In addition to the individual addressee's postulated accident conditions, these items should be reviewed with respect to the scenarios referenced in the generic letter.
NRC REQUESTED INFORMATION Within 120 days of the date of this generic letter, addressees are requested to submit a written summary.report stating actions taken in response to the requested actions noted above, conclusions that were reached relative to susceptibility for waterhammer and two-phase flow in the containment air cooler cooling water system and overpressurization of piping that penetrates containment, the basis for continued operability of affected systems and components as applicable, and corrective actions that were implemented or are planned to be implemented. If systems were found to be susceptible to the conditions that are discussed in this generic letter, identify the systems affected and describe the specific circumstances involved.
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CPCO RESPONSE Actions Taken in Response to the Reguested Determinations Analyses were done to determine the susceptibility of the containment air cooler (CAC) cooling water system to either waterhammer or two-phase flow conditions during any postulated design basis accident (DBA) conditions. While both a Main Steam Line Break (MSLB) and a Loss of Coolant Accident (LOCA) were considered, the LOCA was determined to be limiting when coinciding with a Loss of Offsite Power (LOOP) event.
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At Palisades, three of the four CACs are in service during a OBA The fourth required a separate analysis since it is valved out during a OBA 2
Analyses were also done to identify those piping systems that penetrate containment which may be subject to overpressurization when a confined fluid is thermally expanded. Piping systems where the contained fluid is a gas (steam or air) or where pressure relief is provided are not considered to be susceptible to overpressurization by thermal expansion of the contained fluid.
Conclusions Reached Relative to the Susceptibility for Waterhammer and Two-phase Flow in the Containment Air Cooler Cooling Water System It has been determined that waterhammer could occur in the Service Water (SW) return piping downstream of the CACs (VHX-1, 2, & 3) which are in-service following a OBA The waterhammer loading is bounded by a case where refill is initiated at some time later than the diesel generator start times assumed for a LOOP. It has been determined that waterhammer will not occur in the CACs for the case of a LOCA coincident with a LOOP. However, if the refill occurs at a later time, the water slug from refill would collide with the water slug in the 6 inch discharge line. This waterhammer loading at this location has been determined to be acceptable.
While CAC VHX-4 is isolated during a OBA, it was determined that a steam bubble could form. This could have then resulted in a waterhammer due to a steam bubble collapse when SW is re-initiated. Detailed analyses were not performed to determine the loading magnitude and the impact on piping because a modification was readily available that could prevent the waterhammer from occurring. It was concluded that prevention was more beneficial to the plant than an analysis to show the CAC would not fail. The modification is described below.
The CACs (VHX-1, 2, &3) are susceptible to a short-term two-phase flow during a OBA As discussed below, however, this short-term condition does not prevent the required containment cooling function from being performed.
Conclusions Reached Relative to the Susceptibility for Overpressurization of Piping That Penetrates Containment Two lines associated with the clean waste receiver tanks and a reactor cavity drain line were determined to be susceptible to overpressurization during a OBA These conditions required actions for resolution, which are discussed later.
3 Basis for Continued Operability of Affected Systems and Components Consumers Power Company contracted Sargent & Lundy to perform an operability assessment for the CAC cooling water system and for piping susceptible to overpressurization during DBA conditions. This assessment, titled "Operability Assessment for Transient Conditions at Palisades Nuclear Plant In Response to Generic Letter 96-06," is Sargent & Lundy's Report C-PAL-96-1063-01, Rev. 2 and is contained in Attachment 2 to this letter. The detailed analyses referenced in this report have not been included because of their volume. These are available on site for NRC inspection. to this letter provides an interim operability analysis where the heat removal capability of the CACs is reduced due to two-phase flow conditions.
Corrective Actions That Were Implemented or Are Planned to Be Implemented Several actions have been taken as a result of conditions found during the study of GL 96-06. These include:
(1) The CAC VHX-4 cooling water system piping was modified to change the isolation point during a DBA from the outlet piping to the inlet piping. This change prevents the condition where a steam bubble may form in the CAC, and then suddenly collapse due to the SW being re-initiated. Since the discharge is prevented by a non-return check valve, the CAC will be isolated from SW flow in either direction during a DBA. The steam bubble will therefore collapse slowly as containment is cooled.
As part of the Facility Change that modified the VHX-4 isolation point, procedures were also changed to reflect the revised operation of this system.
(2) Surge pots have been added to clean waste receiver tank piping to prevent the possibility of overpressurization during a DBA.
(3) Procedures controlling the Reactor Cavity Drain Piping have been changed to ensure that the piping will be drained prior to operation.
Although the CAC cooling water system piping has been determined to be operable, additional analysis is necessary to ensure that FSAR design criteria for piping are met and to assess the potential need for additional modifications.
Generic Letter 91-18, "Information to Licensees Regarding Two NRC Inspection
Manual sections on Resolution of Degraded and Nonconforming Conditions and on Operability," was used as guidance for operability determinations.
Identification and Specific Circumstances Involved for Those Systems Found to Be Susceptible 4
The CAC cooling water system for the operable (VHX-1,2, & 3) CACs was susceptible to waterhammer and two-phase flow during a OBA. However, neither of these conditions have been determined to cause these systems to be inoperable. Only the CAC discharge piping is susceptible to waterhammer and this piping was determined to be operable with respect to the waterhammer loads. The two-phase flow has been shown to exist for only a fraction of the time that would be necessary to cause an unacceptable temperature increase within containment.
The CAC cooling water system for the isolated (VHX-4) CAC was shown to be susceptible to waterhammer but this was resolved by a modification to change the isolation valve to the inlet side of the CAC from the outlet.
A reactor cavity drain line and two clean waste receiver tank lines were the only piping systems that penetrate containment that were found to be subject to overpressurization during a OBA temperature rise. The clean waste receiver tank lines were modified by adding surge pots to alleviate that possibility. The reactor cavity drain line is being controlled by procedure to ensure that the line is drained during operation.
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ATTACHMENT 2 CONSUMERS POWER COMPANY PALISADES PLANT DOCKET 50-255 120-DAY RESPONSE TO GL 96-06,.ASSURANCE OF EQUIPMENT OPERABILITY AND CONTAINMENT INTEGRITY DURING DESIGN BASIS ACCIDENT CONDITIONS Sargent & Lundy Report C-PAL-96-1063-01, Rev. xx Operability Assessment for Transient Conditions at Palisades Nuclear Plant In Response to Generic Letter 96-06