ML20127C943
| ML20127C943 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 06/19/1985 |
| From: | Poindexter C BOSTON EDISON CO. |
| To: | Thompson H Office of Nuclear Reactor Regulation |
| References | |
| GL-85-02, GL-85-2, NUDOCS 8506240072 | |
| Download: ML20127C943 (10) | |
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BALTIM ORE GAS AND ELECTRIC CHARLES CENTER P.O. BOX 1475 BALTIMORE, MARYLAND 21203 ARTHUR E. LUNDVALL. JR.
Vict PatsIDENT SuPPLv June 19,1985 U. S. Nuclear Regulatory Commission Office of Nuclear Reactor Regulation Washis.gton, D. C. 20555 ATTENTION: Mr. Hugh L. Thompson, Jr., Director Division of Licensing
SUBJECT:
Calvert Cliffs Nuclear Power Plant Unit Nos.1 & 2; Docket Nos. 50-317 & $0-318 Generic Letter 85-02;" Staff Recommended Actions Stemming From NRC Integrated Program For The Resolution Of Unresolved Safety Issues Regarding Steam Generator Tube Integrity" Gentlemen:
The enclosures provided herein constitute our reply to your request for additional information and a description of our overall progams specified in Generic Letter 85-02.
Enclosure (1) is a description of our programs for assuring steam generator tube integrity and for steam generator tube rupture mitigation. The plant specific programs are described by comparing them to the staff recommended actions presented in the Generic Letter. Enclosure (2) provides the additional information requested concerning category C-2 steam generator tube inspections.
We believe our programs adequately address the concerns expressed in NUREG-0344, "NRC Integrated Program for the Resolution of Unresolved Safety Issues A-3, A-4, and A-5 Regarding Steam Generator Tube Integrity." The programs follow the guidelines presented in Regulatory Guide 1.83 and the SGOG EPRI Report on secondary water chemistry.
8506240072 850619 PDR ADOCK 05000317 P
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June 19,1985 Page 2 Shout ! you have further questions regarding this reply, please do not he :itate to contact us.
Very truly yours,
/
C. H. Poindext for A. E. Lundvall AEL/SRC/sjb cc: D. A. Brune, Esquire G. F. Trowbridge, Esquire D. H. Jaffe, NRC T. Foley, NRC Enclosures
ENCLOSURE 1 9
. REPLY TO NRC GENERIC LETTER 85-02 1.a PREVENTION AND DETECTION OF LOOSE PARTS (INSPECTIONS)
Staff Recommended Action Visual inspections should be performed on the steam generator secondary side of the vicinity of the tube sheet, both along the entire periphery of the tube bundle and along the tube lane, for purposes of identifying loose parts or foreign objects on the tubesheet, and external damage to peripheral tubes just above the tubesheet. An appropriate optical device should be used (e.g., mini-TV camera, fiber optics). Loose parts or foreign objects which are found should be removed from the steam generators. Tubes observed to have visual damage should be eddy current inspected and plugged if found to be defective.
These visual inspections should be performed: (1) for all steam generators at each plant at the next planned outage for eddy current testing, (2) af ter any secondary side modifications, or repairs, to steam generator internals, and (3) when eddy current indications are found in the free span portion of peripheral tubes, unless it has been established that the indication did not result from damage by a loose part or foreign object.
For PWR OL applicants, such inspections should be part of the preservice inspection.
For steam generator models where certain segments of the peripheral region can be shown not to be accessible to an appropriate optical device, licensees and applicants should implement alternative actions to address these inaccessible areas, as appropriate.
Licensees should take appropriate precautions to minimize the potential for corrosion while the tube bundle is exposed to air. The presence of chemical species such as sulfur may aggravate this potential, and may make exposure to the atmosphere inadvisable until appropriate remedial measures are taken.
BG&E Response A visual inspection, for the purpose of identifying loose parts or foreign objects on the tubesheet, has been performed on the secondary side of all Calvert Cliffs steam generators. The inspection was performed utilizing a motorized cart equipped with a mini-TV camera and covered the entire tube bundle periphery and the tube lane.
The need for future visual inspections will be considered as follows:
every outage when the secondary side of the steam generators is opened to perform lancing of the tube sheet sludge pile for sludge removal, after secondary side modifications or repairs when the Quality Assurance / Quality Control Procedures described in item 1.b identify material which cannot be accounted for, and 1
ENCLOSURE 1 when eddy current testing indications are found in the tube sheet area of peripheral tubes if there is reason to believe the indications resulted from a loose part.
The steam generator tubes at Calvert Clifis are normally maintained in a wet lay-up condition. When maintenance conditions do not permit this practice, the time period of dry lay-up is minimized and other industry approved lay-up practices such as nitrogen blanketing are employed. These actions serve to minimize the potential for corrosion due to air presence.
1.b PREVENTION AND DETECTION OF LOOSE PARTS (OUALITY ASSURANCE)
Staff Recommended Action Quality assurance / quality control procedures for steam generators should be reviewed and revised as necessary to ensure that an effective system exists to preclude introduction of foreign objects into either the primary or secondary side of the steam generator whenever it is opened (e.g., for maintenance, sludge lancing, repairs, inspection operations, modifications).
As a minimum, such procedures should include: (1) detailed accountability procedures for all tools and equipment used during an operation, (2) appropriate controls on foreign objects such as eye glasses and film badges, (3) cleanliness requirements, and (4) accountability procedures for components and parts removed from the internals of major components (e.g., reassembly of cut and removed components).
BG&E Response Calvert Cliffs has two programs that control the introduction of foreign objects into the primary and secondary side of the steam generators. Calvert Cliffs Instruction (CCI)-107G " Area Cleanliness Requirements," defines guidelines for establishment of clean areas to prevent degradation of system cleanliness when opening fluid systems as well as the system cleanliness and flushing requirements. Implementation of these guidelines is consistent with ANSI N45.2.1 and N45.2.3. CCI-206F, " Personnel And Material Accountability," provides administrative controls that help prevent the inadvertent intrusion of foreign material into systems which might impair normal operation or cause damage.
Detailed accountability procedures for all tools and equipment used during an operation and for components and parts removed from the system are provided in CCI-206F. This instruction is an effective measure for preventing loose parts and foreign objects from entering safety-related systems.
Cleanliness requirements and control of foreign material are also specified in CCI-107G.
This instruction discusses the consequences of poor material accountability and sets forth the criteria used by the access watch in maintaining area cleanliness and control. In addition, the concept of an access watch is defined along with the inherent responsibilities.
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ENCLOSURE 1 2.a INSERVICE INSPECTION PROGRAM (FULL LENGTH TUBE INSPECTION)
Staff Recommended Action The Standard Technical Specification (STS) and Regulatory Guide 1.83, Part C.2.f, currently define a U-tube inspection as meaning an inspection of the steam generator tube from the point of entry on the hot-leg side completely around the U-bend to the top support of the cold-leg side. The staff recommends that tube inspections should include an inspection of the entire length of the tube (tube end to tube end) including the hot leg side, U-bend, and cold leg side.
This recommended action does not mean that the hot leg inspection sample and the cold leg inspection sample should necessarily involve the same tubes. That is, it does not preclude making-separate entries from the hot and cold leg sides and selecting different tubes on the hot and cold leg sides to meet the minimum sampling requirements for inspection.
Consistent with the current STS requirement, suppplemental sample inspections (af ter the initial 3% sample) under this staff recommended action may be limited to a partial length inspection provided the inspection includes those portions of the tube length where degradation was found during initial sampling.
BG&E Response Baltimore Gas & Electric agrees with the concept of inspecting both cold and hot leg sides of the tubes. Full length tube inspections have been performed at Calvert Cliffs since 1982 and we plan to continue doing so.
2.b INSERVICE INSPECTION PROGRAM (INSPECTION INTERVAL)
Staff Recommended Action The maximum allowable time between eddy current inspections of an Individual steam generator should be !!mited in a manner consistent with Section 4.4.5.3 of the Standard Technical Specifications, and in addition should not extend beyond 72 months.
BG&E Response The maximum allowable time between inservice inspections of steam generator tubes is 40 months pursuant to the Calvert Cliffs Technical Specifications. This is consistent with the frequency of inspection recommended in the CE STS. The inspection intervals specified for each category of inspection results are consistent with the STS. We believe that the Calvert Cliffs Technical Specifications address the concerns expressed in Section 2.2.4 of NUREG-0844. Thus, no further action is deemed necessary.
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ENCLOSURE 1 3.a SECONDARY WATER CHEMISTRY PROGRAM Staff Recommended Action Licensees and applicants should have a secondary water chemistry program (SWCP) to minimize steam generator tube degradation.
The specific plant program should incorporate the secondary water chemistry guidelines in SGOG Special Report EPRINP-2704, "PWR Secondary Water Chemistry Guidelines," October 1982, and should address measures taken to minimize steam generator corrosion, including materials selection, chemistry limits, and control methods. In addition, the specific plant procedures should include progressively more stringent corrective actions for out-of-specification water chemistry conditions. These corrective actions should include power reductions and shutdowns, as appropriate, when excessively corrosive conditions exist. Specific functional individuals should be identified as having the responsibility / authority to interpret plant water chemistry information and initiate appropriate plant actions to adjust chemistry, as necessary.
The referenced SGOG guidelines above were prepared by the Steam Generator Owners Group Water Chemistry Guidelines Committee and represent and consensus opinion of a significant portion of the industry for state-of-the-art secondary water chemistry control.
BG&E Response The secondary water chemistry program at Calvert Cliffs is a site-specific adaptation of the SGOG Special Report mentioned above. The estab!!shment of Action Levels and the notification of key personnel is required by plant procedures.
These procedures have been reviewed and approved by the Plant Operations and Safety Review Committee. The General Supervisor-Chemistry is responsible for interpreting plant water chemistry information and initiating appropriate actions.
3.b CONDENSER INSERVICE INSPECTION PROGRAM Staff Recommended Action Licensees should implement a condenser inservice inspection program. The program should be defined in plant specific safety-related procedures and include:
1.
Procedures to implement a condenser inservice inspection program that will be initiated if condenser leakage is of such a magnitude that a power reduction corrective action is required more than once per three month period; and 2.
Identification and location of leakage source (s), either water or air; 3.
Methods of repair of leakage; 4.
Methodology for determining the cause(s) of leakages; 5.
A preventive maintenance program.
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ENCLOSURE 1 t
BG&E Response
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The integrity of the main condensers is an integral part of our water chemistry program. The condensers are monitored continuously for possible in-leakage by the use of on-line monitors. In the event of a failure of these monitors, an accelerated surveillance program is initiated. If condenser in-leakage is detected, management is notified and appropriate actions are recommended.
1.
General Supervisor-Operations Standing Instruction 81-4 details the procedure to be followed in the emnt of saltwater leakage into the main condenser. It specifies mandatory usage of full available demineralizer capability and power reduction in response to deteriorating feedwater chemistry.
If feedwater chemistry cannot be maintained within specifications, the unit must be shutdown until repairs to the main condenser are effected.
The recent replacement of the original copper-nickel condenser tubes with AL-6X (Unit
- 1) and Titanium (Unit 2) is evidence of our commitment preserving condenser integrity.
2.
The condensate and feedwater systems are continuously monitored for conductivity and sodium concentration to provide early detection of saltwater entry into the main condenser. If such leakage is detected, the suspect tube bundle is removed from service and the leeking tube (s) identified by application of foam and/or helium leak detection. Air leakage into the main condenser is measured every four hours and the results trended. As appropriate, air leaks are located using helium leak detection.
3.
Leaking condenser tubes are plugged using either wood or rubber plugs. Should leaking tubes be removed from the condenser for metallurgical examination, they are replaced by dummy tubes ro!!ed into the tube sheet.
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Should a condenser tube fall in service, the cause of the failure would normally be determined by the use of eddy current testing and/or removal of the tube for metallurgical examination.
5.
The integrity and efficiency of the main condensers is maintained by bulleting of the tubes, operation of Amertap condenser tube cleaning systems, periodic eddy current examinations of condenser tubes, and periodic inspection of condenser internals.
4.
PRIMARY TO SECONDARY LEAKAGE LIMIT Staff Recommended Action All PWRs that have Technical Specifications limits for primary-to-secondary leakage rates which are less restrictive than the Standard Technical Specifications (STS) limits should implement the STS !!mits.
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ENCLOSURE 1 BG&E Response The Technical Specifications at Calvert Cliffs state that the Reactor Coolant System (RCS) leakage shall be limited to No Pressure Boundary Leakage 1 gpm Unidentified Leakage 1 gpm Total Primary-to-Secondary Leakage Through Steam Generators, and 10 gpm Identified Leakage From The RCS Steam generator leakage to the secondary system is defined as a type of Identified Leakage.
The CE STS limits are similar to those at Calvert Cliffs except that the STS limits the leakage through each individual steam generator to that specified below.
Primary-to-secondary leakage is limited to I gpm total through all steam generators not isolated from the RCS and 500 gallons per day (gpd) through any one steam generator not isolated from the RCS.
There appears to be little or no technical justification for the 500 gpd limit for plants that cannot isolate their steam generators.
The value was originally developed for Westinghouse tubes and may not apply to Calvert Cliffs.
Consequently, we see no reason to adopt this apparently arbitrary limit.
5.
COOLANT IODINE ACTIVITY LIMIT Staff Recommended Action PWRs that have Technical Specifications limits and surveillance for coolant iodine activity that are less restrictive than the Standard Technical Specification (STS) should implement the STS limits. Those plants identified above that also have low head high pressure safety injection pumps should either: (1) implement lodine limits which are 20% of the STS values, or (2) implement reactor coolant pump trip criteria which will ensure that if offsite power is retained, no loss of forced reactor coolant system flow will occur for steam generator tube rupture events up to and including the design basis double-ended break of a single steam generator tube, and implement lodine limits consistent with the STS.
BG&E Response Technical Specification 3.4.8 limits the specific activity of the primary coolant to:
less than or equal to 1.0 microcurle/ gram DOSE EQUIVALENT I-131, and less than or equal to 100/E microcuries/ gram.
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ENCLOSURE 1 I
These activity limits are identical to those specified in the CE STS. In addition, Surveillance Requirements 4.4.8 are identical to those in the CE STS. Although our Technical Specification limits and surveillance requirements for coolant lodine activity are very similar to the STS, we also have reactor coolant pump trip procedures that comply with item (2) in the above Staff Recommended Action.
Because the concerns of Section 2.9 of NUREG-0844 are addressed, we feel no further changes or actions are necessary.
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SAFETY IN3ECTION SIGNAL RESET i
Staff Recommended Action The control logic associated with the safety injection pump suction flow path should i
be reviewed and modified as necesssary, by licensees, to minimize the loss of safety function associated with safety injection reset during an SGTR event. Automatic switchover of safety injection pump suction from the boric acid storage tanks (BAST) to the refueling water storage tanks should be evaluated with respect to 3
whether the switchover should be made on the basis of low BAST level alone without consideration of the condition of the SI signal.
BG&E Response This item does not apply to Calvert Cliffs. A Safety injection Actuation Signal (SIAS) starts charging pumps. These pumps draw suction from the BAST. Safety injection Actuation System also starts High Pressure Safety injection pumps which draw suction from the Refueling Water Storage Tanks (RWST). Two-out-of-four low level signals for the RWST causes a Recirculation Actuation Signal which allows HPSI Pump suction from the containment sump. No resets will prevent suction from the sump as long as two-out-of-four low level RWST signals persist.
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F ENCLOSURE 2 REQUEST FOR INFORMATION CONCERNING CATEGORY C-2 STEAM GENERATOR TUBE INSPECTIONS Information Requested The enclosed draf t NUREG-08M Section 2.2.1.2 describes certain limitations which the staff believes to be inherent in the present Technical Specification steam generator ISI requirements pertaining to Category C-2 inspection results. Licensees and applicants are requested to provide a description of their current policy and actions relative to this issue and any recommendations they have concerning how existing Technical Specification steam generator ISI requirements pertaining to Category C-2 inspection results could be improved to better ensure that adequate inspections will be performed.
This description should include a response to the following questions:
1.
What factors do, or would, the licensee or applicant consider in determing (a) whether additional tubes should be inspected beyond what is required by the Technical Specifications, (b) whether all steam generators should be included in the inspection program, and (c) when the steam generators should be reinspected?
2.
To what extent do these factors include consideration of the degradation mechanism itself and its potential for causing a tube to be vulnerable to rupture during severe transients or postulated accident before rupture or leakage of that tube occurs during normal operation?
BG&E Response In the event of Category C-2 eddy current inspection results, the Calvert Cliffs Steam Generator Integrity Task Force would meet to decide the course of action to be taken.
Actions taken could include: 1) Additional eddy current testing of more steam generator tubes, 2) metallurgical examination of tubes containing eddy current indications, and 3) preventative measures to avert further degradation. Factors which would be considered in determining whether additional tubes should be tested beyond Technical Specification Requirements are:
1)
The type of degradation mechanism which is believed to be occurring, 2) the severity of the degradation which has been found, 3) If predictable, the growth rate of the degradation,4) the number of tubes tested at that point in time, and 5) whether or not the degradation appears to be concentrated in a particular area of the tube bundle.
In past outages, the number of tubes tested by eddy current have exceeded the number required by the Technical Specifications. The need to inspect all steam generators would be evaluated on a case by case basis. In general, we believe all steam generators at Calvert Cliffs behave in a similar manner. Since 1982, we have considered it general practice to inspect both steam generators on the affected unit every refueling outage. However, when the tube degradation mechanism can be isolated to a single steam generator (i.e., damage caused by loose parts or foreign objects),
lengthy inspections of the other generator would be unnecessary.