A04820, Forwards Rev 0 to Nuclear Engineering & Operating Procedure Neo 2.17, Secondary Water Chemistry Program, Per Generic Ltr 85-02 Request for Description of Overall Program for Assuring Steam Generator Tube Integrity

Forwards Rev 0 to Nuclear Engineering & Operating Procedure Neo 2.17, Secondary Water Chemistry Program, Per Generic Ltr 85-02 Request for Description of Overall Program for Assuring Steam Generator Tube Integrity

ML20128M372
Person / Time
Site:	Millstone, Haddam Neck, 05000000
Issue date:	06/25/1985
From:	Opeka J CONNECTICUT YANKEE ATOMIC POWER CO., NORTHEAST NUCLEAR ENERGY CO., NORTHEAST UTILITIES
To:	Thompson H Office of Nuclear Reactor Regulation
Shared Package
ML20128M376	List: A04820, Forwards Rev 0 to Nuclear Engineering & Operating Procedure Neo 2.17, Secondary Water Chemistry Program, Per Generic Ltr 85-02 Request for Description of Overall Program for Assuring Steam Generator Tube Integrity ML20128M412
References
A04820, A4820, GL-85-02, GL-85-2, TAC-58070, NUDOCS 8507110694
Download: ML20128M372 (36)

Text

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HAR IFORD. CONNECTICUT 06141-0270 k L J 7,[,',l'CM,[,C, (203) 665-5000 June 25,1985 Docket No. 50-213 50-336 50-423 A04820 Director of Nuclear Reactor Regulation Attn: Mr. Hugh L. Thompson, Director Division of Licensing U. S. Nuclear Regulatory Commission Washington, D. C. 20555

Reference:

(1) H. L. Thompson Generic Letter 85-02 to all PWRs, dated April 17,1985.

Gentlemen:

Haddam Neck Plant Millstone Nuclear Power Station, Unit Nos. 2 and 3 Response to Generic Letter 85-02 Steam Generator Tube Integrity in Reference (1) the Staff issued Generic Letter 85-02 to all PWR licensees and applicants for operating licenses. In Generic Letter 85-02 the Staff requested that a description of a plant's overall program for assuring steam generator tube integrity and steam generator tube rupture mitigation be provided.

Accordingly, Connecticut Yankee Atomic Power Company (CYAPCO) and Northeast Nuclear Energy Company (NNECO) hereby provide the requested l

program descriptions for the Haddam Neck Plant and Millstone Unit Nos. 2 l

and 3. The program descriptions are structured to allew for a ready comparison to the Staff's recommended actions presented in Enclosure I to Generic Letter 85-02. The Haddam Neck response is provided as Attachment 1, Millstone Unit No. 2 as Attachment 2 and Millstone Unit No. 3 as Attachment 3.

CYAPCO's and NNECO's programs, for assuring steam generator tube integrity and steam generator tube rupture mitigation, are consistent with the intent of the Staff's recommended actions regarding steam generator tube integrity.

There are no changes planned to the attached CYAPCO and NNECO programs as a result of Generic Letters 85-02 or Draf t NUREG-0844.

(\ no 8507110694 850625 PDR ADOCK 05000213 P PDR t -

7 r 2-We trust you will find this information satisfactory.

Very truly yours, CONNECTICUT YANKEE ATOMIC POWER COMPANY NORTHEAST NUCLEAR ENERGY COMPANY

3. F. O'pekh 50h v Senior Vice President cc: Mr. Emmett Murphy Operating Reactors Assessment Branch Mr. John A. Zwolinski, Chief Operating Reactors Branch #5 Mr. Edward 3. Butcher, Chief Operating Reactors Branch #3 Mr. B. Joe Youngblood, Chief Licensing Branch f1 t

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Docket No. 50-213 Attachment 1 Haddam Neck Plant Response to Generic Letter 85-02 June,1985

I E Attachment 1: Haddam Neck Response to GL 85-02 ITEM la-Prevention and Detection of Loose Parts (Inspections)

Visual examinations of the steam generators have been conducted during refueling outages at Haddam Neck.

Fiberoptics or TV techniques are used to inspect the outer annulus and tubelane for foreign objects and other anomalies. The inspection is usually performed af ter tubesheet cleaning has been completed. Any significant foreign materials found during these examinations, which could cause tube damage, are removed.

Steam generator secondary side chemistry is closely controlled during operation and shutdown periods. During refueling shutdowns the steam generators are maintained in wet lay up whenever practicable and are maintained under a nitrogen blanket when personnel access to the secondary side is not required.

When combined with a stringent chemistry control program during operation, these actions assure that the tube bundle is not exposed to aggressive corrosive attack during maintenance periods.

The need for additional visual inspections for loose parts will be evaluated based on the amount of secondary side maintenance performed since the last inspection. This would involve a plant specific case-by-case evaluation.

Emphasizing prevention of loose parts through QA/QC procedures as well as general housekeeping controls (for S/G and adjacent systems work) is effective, inexpensive, and in line with ALAR A considerations.

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I i ITEM lb--Prevention and Detection of Loose Parts (Quality Assurance)

Procedures are in place to preclude introduction of foreign objects into the steam generators at Haddam Neck. These procedures are issued as part of the standing instructions for conduct of outage work. They provide instructions for maintaining accountability of materials introduced into the steam generators, maintaining appropriate cleanliness in Foreign Material Exclusion Areas, preventing the inadvertent introduction of foreign material into the steam generator, and accounting for all materials disassembled within or removed from the steam generator. These instructions are normally incorporated as a part of the Work Order which directs the conduct of work inside the steam generator.

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7 e n ITEM 2a--Inservice Inspection Program (Full Length Tube Inspection)

The technical specifications specify requirements for eddy current testing of the steam generator tubes at Haddam Neck during inservice inspections. In addition to these requirements, at least three percent of the tubes are inspected over the full length of the tube. Any supplemental inspections (after the initial sample) are typically limited to those portions of the tube length where degradation is found during initial sampling.

I C ITEM 2b--Inservice Inspection Program (Inspection Interval)

At Haddam Neck, i.1 service inspections of the steam generator tubes are performed at intervals of not less than 12 nor more than 24 calendar months af ter the previous inspection. If two consecutive inspections (af ter the initial preservice inspection) result in all inspection results falling within Category Ci, or if two consecutive inspections demonstrate that previously observed degradation has not continued and no additional degradation has occurred, the inspection interval may be extended to a maximum of once per 40 months.

If the results of the inservice inspection of a steam generator conducted at 40 month intervals fall into Category C3, the inspection frequency will be increased to at least once per 20 months. The increase in inspection frequency shall apply until subsequent inspections qualify an extension to a 40 month interval.

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ITEM 3a-Secondary Water Chemistry Program The secondary water chemistry program at Haddam Neck is based on the guidelines in the Steam Generator Owner's Group (SGOG) Special Report EPRI-NP-2704, Rev.1, and the NSSS vendor recommendations. The recently approved corporate secondary water chemistry program covering Haddam Neck is provided as Attachment IA.

ITEM 3b--Condenser Inservice Inspection Program Haddam Neck employs various procedures to minimize and monitor the degradation of steam generator tubes due to condenser tube leakage of oxygen, cooling water and other impurities. Chemistry pro:edures specify when power reductions must occur, and then corrective actions are implemented. Normally, a power reduction is performed before any of the required limits in the procedures are reached. In this way, power is dropped to a level sufficient for removal of one of the four plant condenser water boxes from service to locate and plug the leaking tube. Identification of the leaking tube (or tubes) is done using Helium leak detection equipment or by performing a soap test on the tubes of each waterbox taken out of service. We also monitor air ejector flow rate as an indication of condenser air inleakage. When a tube is identified it is then plugged to remove it from service. No other repairs are performed.

Eddy current testing is performed on a sample of tubes each outage to determine the causes of tube degradation, it is performed as preventive maintenance so that tubes with a potential to fail can be plugged to forestall any power reductions or out of specification chemistry condition during the following cycle.

In addition, tubes have been pulled from the waterboxes for destructive testing and metallurgical examination.

Haddam Neck has been systematically removing copper alloy tubing from secondary plant components to minimize deleterious effects on steam generator tubes. At present, all of the copper alloy tubing in Haddam Neck's condenser has been replaced with stainless steel tubing. Four heaters in the feedwater train still contain copper alloy tubing (other than these four heaters, all tubes are stainless steel).

As a final preventive maintenance act, the inside of the condenser tubes are brushed clean using a small brush, then air is blown the length of the condenser tube.

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ITEM 4--Primary to Secondary Leakage Limit

'Haddam Neck Technical Specification limits (and forthcoming proposed Haddam Neck Standard Technical Specifications) for primary to secondary leakage are 0.4 gpm total primary to secondary leakage through all steam generators not isolated from the reactor coolant system and 150 gallons per day through any one steam generator not isolated from the reactor coolant system. These limits are more conservative than Standard Technical Specification limits of I gpm and 500 gpd respectively. In addition, Haddam Neck's steam generator tubes are smaller (0.75 in. dia as opposed to 0.85 in, dia.) and thicker (.055 in. thick as opposed to .050 in. thick) which renders these limits even more conservative than is the case for a typical steam generator tube. Haddam Neck limits are more conservative than the Staff's recommendations concerning this item.

ITEM 5--Coolant Iodine Activity Limit This item requested all PWR's to implement the Standard Technical Specification (STS) LCO and Surveillance for coolant iodine activity. In addition, it proposes for plants with low-head High Pressure Safety Injection (HPSI) pumps either (1) implement iodine limits that are 20 percent of STS values or (2) implement reactor coolant pump trip criteria to retain forced reactor coolant flow during a steam generator tube rupture event and implementation of the STS iodine limits.

The current draf t of the Standard Technical Specifications for Haddam Neck set limits for both iodine and overall maximum activity and also specify a surveillance program.

Haddam Neck has low-head High Pressure Safety injection pumps.

Implementation of the STS limit of 1.0 uci/g lodine activity is feasible for this plant. However, reducing the iodine 131 activity limit to 20 percent of the STS limit, or 0.20 uci/g, is not acceptable. Iodine activity at this plant has been measured only for trending purposes. Instances have occurred where iodine activity has exceeded 20 percent of the STS limits. If the staff recommended action were required, this would have necessitated lengthy shutdowns of the plant, when in fact they were deemed unnecessary at the time, according to current activity limits. These limits are based on conservative estimates of possible primary coolant leakage during a postulated double-ended steam generator wbe rupture. However, the plant has not experienced lodine spiking that even approached the 60 uci/g dose-equivalent iodine 131, which is the assumed level necessary for exceeding 10 CFR part 100 guideline doses.

The NRC's other proposal, implementation of reactor coolant pump trip criteria to maintain forced coolant flow (if offsite power is retained) in the event of a design basis tube rupture, is also unwarranted. Currently, procedures for steam generator tube rupture specify that all Reactor Coolant Pumps (RCP's) be stopped when the Reactor Coolant System pressure drops below 1700 psig and the HPSI pumps are operating.

Once the event has been determined to be a tube failure, and the faulted steam generator has been positively identified, then one of the RCP's can be restarted so that pressurizer spray can be used, if certain conditions are met for RCP operation. Also, auxiliary spray may be used to depressurize the RCS instead of the power operated relief valves. To minimize the RCS leak rate, the reactor coolant pressure is reduced to the pressure of the faulted steam generator with at least 50 F subcooling. A reactor coolant pump is restarted at this point if its operating conditions are met. The HPSI pumps are shutdown when the pressurizer level is above 35 percent, the RCS is at least 500F subcooled, and natural circulation cooling is verified.

ITEM 6--Safnty inlictirn Sign-1 Reset At Haddam Neck, the Refueling Water Storage Tank (RWST) is the primary source of water for the Emergency Core Coolant System. The safety injection pumps take a normal suction from the RWST. No transfer to the RWST from any intermediate tank is required.

The action recommended by the NRC Staff concerning Safety injection Signal Reset is not appropriate for Haddam Neck.

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C-2 CATEGORY TUBES I-The current policy for eddy current testing (ECT) at Haddam Neck requires that the inspection be performed according to the plant technical specifications at intervals which are at least as restrictive as the standard technical specifications (STS). The initial inspection sample size is 3 percent and the inspection is expanded, according to STS requirements, if test results indicate "C2" or "C3" categcry findings. This inspection policy has been found to be adequate to ensure steam generator (SG) tube integrity.

The additional tubes tested as a result of a "C-2" category are selected from problem areas, thus increasing the likelihood of identifying degraded tubes. If a degraded condition is widespread, it is highly probable that the STS method of expanding the test sample will, in fact, lead to a 100 percent test program. The effectiveness of this technique has been proven in that past inspections that were expanded to "C-2" but not "C-3" have not led to excessive degradation over the subsequent cycle.

The need to inspect other SGs at the same unit is evaluated on a case-by-case basis. If a particular mode of tube degradation is identified and isolated to a single SG, then unnecessary, additional expense and radiation exposure is avoided by not expanding the inspection to other SGs.

The current ECT inspection' policy has been found to be adequate to ensure SG tube integrity. The step-wise expansion of the sample size has been very effective in the monitoring of the condition of the tubes.

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Docket No. 50-336 Attachment 2 Millstone Nuclear Power Station, Unit No. 2 Response to Generic Letter 85-02 i

I June,1985

Attachment 2: Millstone Unit No. 2 Response to Generic Letter 85-02 ITEM la-Prevention and Detection of Loose Parts (Inspections)

Visual examinations of the steam generators have been conducted during refueling outages at Millstone Unit No. 2.

Fiberoptics or TV techniques are used to inspect the outer annulus and tubelane for foreign objects and other anomalies. The inspection is usually performed af ter tubesheet cleaning has been completed. Any significant foreign materials found during these examinations, which could cause tube damage, are removed.

Steam generator secondary side chemistry is closely controlled during operation and shutdown periods. During refueling shutdowns the steam generators are maintained in wet lay up whenever practicable and are maintained under a nitrogen blanket when personnel access to the secondary side is not required.

When combined with a stringent chemistry control program during operation, these actions assure that the tube bundle is not exposed to aggressive corrosive attack during maintenance periods.

The need for additional visual inspections for loose parts will be evaluated based on the amount of secondary side maintenance performed since the last inspection.

This would involve a plant specific case-by-case evaluation. Emphasizing prevention of loose parts through QA/QC procedures as well as general housekeeping controls (for S/G and adjacent systems work) is effective, inexpensive, and in line with ALAR A considerations.

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ITEM lb--Prevention and Detection of Loose Parts (Quality Assurance)

Procedures are in place to preclude introduction of foreign objects into the steam generators at Millstone Unit No. 2. These procedures are issued as part of the standing instructions for conduct of outage work. They provide instructions for _ maintaining accountability of materials introduced into the steam generators, maintaining appropriate cleanliness in Foreign Material Exclusion Areas, preventing the inadvertent introduction of foreign material into the steam generator, and accounting for all materials disassembled within or removed from the steam generator. These instructions are incorporated as a part of every Work Order which directs the conduct of work inside the steam generator.

ITEM 2a--Inservice Inspection Program (Full Length Tube Inspection)

The technical specifications specify requirements for eddy current testing of the steam generator tubes at Millstone Unit No. 2 during inservice inspections. In addition to these requirements, at least three percent of the tubes are inspected over the full length of the tube. Any supplemental inspections (after the initial sample) are typically limited to those portions of the tube length where

~ degradation is found during initial sampling.

ITEM 2b--inservice Inspection Program (Inspection Interval)

At Millstone Unit No. 2, inservice inspections cf the steam generator tubes are performed at intervals of not less than 12 nor more than 24 calendar months af ter the previous inspection. If two consecutive inspections (after the initial preservice inspection) result in all inspection results falling within Category C1, or if two consecutive inspections demonstrate that previously observed degradation has not continued and no additional degradation has occurred, the inspection interval may be extended to a maximum of once per 40 months.

If the results of the inservice inspection of a steam generator conducted at 40 month intervals fall into Category C3, the inspection frequency will be increased to at least once per 20 months. The increase in inspection frequency shall apply until subsequent inspections qualify an extension to a 40 month interval.

4 ITEM 3a--Secondary Water Chemistry Program The secondary water chemistry program at Millstone Unit No. 2 is based on the guidelines- in the Steam Generator Owner's Group (SGOG) Special Report EPRI-NP-2704, Rev. i, and the NSSS vendor recommendations. The recently approved corporate secondary water chemistry program covering Millstone Unit No. 2 is provided as Attachment 2A.

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ITEM 3b--Condenser Inservice Inspection Program A comprehensive condenser inservice inspection program is in place at Millstone Unit No. 2. Operating chemistry guidelines specify stringent corrective action levels for either salt water or air leakage. As a result of the inservice inspection program, condenser air inleakage has been maintained at less than three cubic feet per minute and condensate oxygen levels are consistently below eight parts per billion. Eddy current examination of 100 percent of the condenser tubing is usually conducted during each refueling outage. Tubes which show degradation, such that failure could occur during the subsequent operating cycle, are removed from service by plugging.

Titanium tubing is planned to be substituted for the present copper nickel alloy during the 1986 refueling outage. Titanium's high resistance to corrosion will assure optimum tube integrity and preclude deleterious effects associated with copper.

During some refueling shutdowns the condenser may be cleaned using high pressure water lances. Tubes which cannot be fully examined are plugged as a preventive measure. These procedures and practices will be continued to assure continued long term condenser integrity.

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ITEM 4--Primary to Secondary Leakage Limit Millstone Unit No. 2 Technical Specifications currently allow one GPM total primary to secondary leakage, 0.5 GPM maximum per steam generator. The 0.5 GPM per steam generator limit corresponds to 720 gallons of primary to secondary leakage per day. The Standard Technical Specifications allow one GPM total primary to secondary leakage with 500 gallons per day (approximately 0.35 GPM) through any one steam generator. Thus the one difference between Millstone Unit No. 2 Technical Specifications and the Standard Technical Specification is the higher allowed leakage through one steam generator of 720 gallons per day versus 500 gallons per day.

NUREG-0844 indicates that the basis for the 500 gallons per day limit is associated with leak rate and burst test data for 0.875 inch outside diameter by 0.050 inch thick Westinghouse tubes. The Standard Technical Specification limit

/ ensures that through wall cracks leaking at the leak rate limit during normal

/ operation have sufficient residual integrity to sustain . postulated accident loadings such as a Main Steam Line Break or LOCA without causing a tube rupture. This leakage limit is conservative for tubes with a smaller diameter and wall thickness, as found in Millstone Unit No. 2 steam generators (0.750 inch outside diameter by 0.048 inch thick).

In addition, the Millstone Unit No. 2 steam generators are not intended to be

/- leak tight, as the tube sleeves are by design leak limiting. Since some small

/ leakage will be expected at Millstone Unit No. 2, the unit is different from most other PWR's.

Northeast Nuclear Energy Company has determined that a 0.5 GPM limit at Millstone Unit No. 2 is adequate to ensure that steam generator tube integrity is maintained in the event of a main steam line break or a loss-of-coolant accident, thus this limit is both justified and necessary at Millstone Unit No. 2.

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ITEM 5--Coolant Iodine Activity Limit A review of the STS and Millstone Unit No. 2 Technical Specification shows that current specifications are already consistent with the STS LCO's and survei!!ance on coolant iodine activity.

Millstone Unit No. 2 has low-head High Pressure Safety Injection (HPSI) pumps.

The Technical Specification minimum HPSI pump discharge pressure is 1125 psig and normal discharge pressure is 1250 psig. Implementation of iodine limits corresponding to 20% of the STS iodine limits would be unacceptable to the operation of the unit. Reducing the current I uci/gm dose equivalent I-131 limit to 0.2 uci/gm could cause unwarranted shutdowns. The unit has had fuel failures in their last two operating cycles corresponding to approximately 0.1% failed fuel (2 'to 3 dozen fuel pins). Steady state full power operation has produced about 0.1 uci/gm dose equivalent I-131 with this failed fuel. However, at-power transient operation has produced iodine levels up to 0.5 uci/gm dose equivalent I-131. Unlike the 60 uci/gm reactor coolant system dose equivalent I-131 assumed in NUREG-0844 for a steam generator tube rupture, the maximum dose equivalent I-131 seen at Millstone Unit No. 2, for any mode of operation or shutdown is approximately 3 uci/gm. This was from an iodine spike following a full power trip. This demonstrates that lowering the coolant system iodine limits to 20% of the STS limits would have a major impact on operation of the unit but peak iodine levels will still be far from the 60 uci/gm assumed level. The iodine spiking assumptions are unnecessarily conservative. Implementation of the reduced iodine limits is not warranted.

The alternative proposed by the NRC, implementation of reactor coolant pump trip criteria that maintains forced coolant flow during a steam generator tube rupture (SGTR) is also not warranted.

Millstone Unit No. 2 Emergency Operating Procedures (EOP's) currently require the tripping of all four reactor coolant pumps (RCPs) if pressurizer pressure decreases to 1600 psia. This action is consistent in both the optimal event specific and functional EOP's. This strategy is based on certain LOCA transients which have worse consequences if RCP's are lef t running. Having a consistent RCP trip criterion ensures a conservative approach since the initial event diagnosis may be difficult. It should be noted that the EOP's specify that one RCP in each loop be restarted when RCS conditions are satisfactory for RCP operation. These conditions include adequate net positive suction head, seal cooling water, pressurizer level, subcooling, and steam generator heat removal.

Millstone Unit No. 2 is currently evaluating a " trip two-leave two" RCP trip criterion that maintains forced RCS flow for non-LOCA events and for a broader range of RCS conditions. We are not in a position to demonstrate that this strategy, if implemented, would ensure RCS forced flow during design basis steam generator tube rupture events. This is due to the need to ensure RCP operating parameters are not exceeded, which may occur during a design basis steam generator tube rupture event.

NUREG-0844 concluded that plants with low-head HPSI pumps were more likely to have dose consequences similar to 10 CFR 100 limits since high-head HPSI plants would be less likely to lose RCS pressure to the point where RCP's would need to be tripped. This in turn would allow lower RCS pressure for the same

subcooling. This would limit leak flow to the secondary side minimizing the release. NUREG-0844 (Section 2.9) was also concerned with loss of main pressurizer spray necessitating use of power operated relief valves to depressurize, thus increasing the probability of a LOCA further complicating the event.

Millstone Unit No. 2 has addressed and mitigated these problems as follows:

1. Auxiliary spray is available from a positive displacement charging pump to

' depressurize the RCS rather than use the power operated relief valves.

2. High head safety grade charging pumps (assumed to deliver 40 GPM each) automatically act to maintain RCS inventory as well as being started on a safety injection signal. Three charging pumps are available; the Technical Specification requires two to be operable, one on each facility.

3. EOP's specify RCP restart criteria so that af ter a steam generator tube rupture is confirmed as the accident in progress, RCP's would be restarted when required prerequisites were met.

4. To minimize overfill of the steam generator secondary side, such as occurred at Ginna, the EOP for steam generator tube rupture minimizes the RCS leak rate by:

a. Using the operating loop temperature for subcooling calculation.

b. Restarting RCP's if possible.

c. Throttling HPSI when termination criteria are met (steam generator heat removal, pressurizer level greater than 35% and RCS subcooling greater than 20 degrees F.)

d. Reducing RCS pressure until RCS pressure equals steam generator pressure or 20 degrees subcooling is reached. RCS voiding is tolerated as long as it is verified not to inhibit adequate core cooling.

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. ITEM 6--Safety injection Signal Reset

-At Millstone Unit No. 2, the Refueling Water Storage Tank (RWST) is the

, primary source of water for the Emergency Core Coolant System. The safety injection pumps take a normal suction from the RWST. No transfer to the RWST from any intermediate tank is required.

The action . recommended by the NRC Staff concerning Safety Injection Signal Reset is not appropriate for Millstone Unit No. 2.

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C-2 CATEGORY TUBES The current policy for eddy current testing (ECT) at Millstone Unit No. 2 requires that the inspection be performed according to the plant technical specifications at intervals which are at least as restrictive as the standard technical specifications (STS). The initial inspection sample size is 3 percent and the inspection is expanded, according to STS requirements, if test results indicate "C2" or "C3" category findings. This inspection policy has been found to be adequate to ensure steam generator (SG) tube integrity.

The additional tubes tested as a result of a "C-2" category are selected from problem areas, thus increasing the likelihood of identifying degraded tubes. If a degraded condition is widespread, it is highly probable that the STS method of expanding the test sample will, in fact, lead to a 100 percent test program. The effectiveness of this technique has been proven in that past inspections that were expanded to "C-2" but not "C-3" have not led to excessive degradation over the subsequent cycle.

The need to inspect other SGs at the same unit is evaluated on a case-by-case basis, if a particular mode of tube degradation is identified and isolated to a single SG, then unnecessary, additional expense and radiation exposure is avoided by not expanding the inspection to other SGs.

The current ECT inspection policy has been found to be adequate to ensure SG tube integrity. The step-wise expansion of the sample size has been very effective in the monitoring of the condition of the tubes.

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Docket No. 50-423 Attachment 3 Millstone Nuclear Power Station, Unit No. 3 Response to Generic Letter 85-02 June,1985 s

Attachment 3: Millstone Unit No. 3 Response to Generic Letter 85-02 ITEM la-Prevention and Detection of Loose Parts (Inspections)

Millstone Unit No. 3 has completed a preservice visual inspection of the secondary side of the steam generators in the vicinity of the tube sheet, both along the entire periphery of the tube bundle and along the tubelane.

Fiberoptics or TV techniques will be used to inspect the outer annulus and tubelane for foreign objects and other anomalies. The inspection will usually be performed after tubesheet cleaning has been completed. Any significant foreign materials found during these examinations, which could cause tube damage, will be removed.

Steam generator secondary side chemistry is closely controlled during operation and shutdown periods. During refueling shutdowns the steam generators will be maintained in wet lay up whenever practicable and will be maintained under a nitrogen blanket when personnel access to the secondary side is not required.

When combined with a stringent chemistry control program during operation, these actions assure that the tube bundle is not exposed to aggressive corrosive attack during maintenance periods.

The need for additional visual inspections for loose parts will be evaluated based on the amount of secondary side maintenance performed since the last l inspection. This would involve a plant specific case-by-case evaluation.

Emphasizing prevention of loose parts through QA/QC procedures as well as general housekeeping controls (for S/G and adjacent systems work) is effective, inexpensive, and in line with ALARA considerations.

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ITEM lb--Prevention and Detection of Loose Parts (Quality Assurance)

Procedures are in place to preclude introduction of foreign objects into the steam generators at Millstone Unit No. 3. These procedures provide instructions for maintaining accountability of materials introduced into the steam generators, maintaining appropriate cleanliness in Foreign Material Exclusion Areas, preventing the inadvertent introduction of foreign material into the steam generator, and accounting for all materials disassembled within or removed from the steam generator. These instructions are ir.corporated as a part of every Work Order which directs the conduct of work inside the steam generator.

ITEM 2a--Inservice Inspection Program (Full Length Tube Inspection)

The technical specifications specify requirements for eddy current testing of the steam generator tubes at Millstone Unit No. 3 during inservice inspections. In addition to these requirements, at least three percent of the tubes are inspected over the full length of the tube. Any supplemental inspections (after the initial sample) are typically limited to those portions of the tube length where degradation is found during initial sampling.

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ITEM 2b--Inservice Inspection Program (Inspection Interval)

The first inservice inspection of the steam generator tubes at Millstone Unit No. 3 will take place af ter six effective full power months but within 24 calendar months of initial criticality. The inservice inspections at Millstone Unit No. 3 will take place at intervals of not less than 12 nor more than 24 calendar months af ter the previous inspection. If two consecutive inspections (after the initial preservhe ihspection) result in all inspection results falling within Category Cl, or if two consecutive inspections demonstrate that previously observed degradation has not continued and no additional degradation has occurred, the inspection interval may be extended to a maximum of once per 40 months.

If the results of the inservice inspection of a steam generator conducted at 40 month intervals fallinto Category C3, the inspection frequency will be increased to at least once per 20 months. The increase in inspection frequency shall apply until subsequent inspections qualify an extension to a 40 month interval.

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ITEM 3a--Secondary Water Chemistry Program The secondary water chemistry program at Millstone Unit No. 3 is based on the guidelines in the Steam Generator Owner's Group (SGOG) Special Report EPRI-NP-2704, Rev.1, and the NSSS vendor recommendations. The recently approved corporate secondary water chemistry program covering Millstone Unit No. 3, when operational, is provided as Attachment 3A.

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ITEM 3b--Condenser Inservice Inspection Program On Millstone Unit No. 3, operating guidelines will specify corrective action levels for either salt water or air inleakage. The approach will be to identify and correct inleakage problems, to identify the cause of the problems and to implement additional preventive maintenance or inspections as required to eliminate or control the problems in the future. Millstone Unit No. 3 is also planning on an Inservice Inspection Program to establish eddy current testing of j condenser tubes during outages. Baseline testing of sample tubes will be done prior to commercial operation.

The tubing material used in Millstone Unit No. 3's condenser is titanium, providing optimum corrosion resistance and avoiding deleterious copper contributions to the secondary water chemistry.

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-e .o ITEM 4--Primary to Secondary Leakage Limit The draf t Technical Specifications for Millstone Unit No. 3, as they relate to primary to secondary leakage, incorporate the limits stated in the STS for Westinghouse PWR's. The one GPM total leakage supports the assumptions used in the accident analyses. The 500 gallons per day leakage from any one steam generator was developed on leak rate and burst test data for 0.875 inch OD by 0.050 inch thick Westinghouse tubes. This limit is conservative for tubes with a smaller diameter and wall thickness which is the case in the Millstone Unit No. 3 generators. The draft technical specifications have been submitted to the NRC.

Millstone Unit No. 3 is in compliance with this staff recommended action.

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F-4 o ITEM 5--Coolant Iodine Activity Limit The draf t Technical Specifications for Millstone Unit No. 3, as they relate to coolant iodine activity, incorporate the limits stated in the STS for Westinghouse l PWR's. These support the assumptions used in the accident analyses. The plant design includes high head ECCS pumps, so no additional restrictions on lodine activity need be implemented.

Millstone Unit No. 3 is in compliance with this staf f recommended action.

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ITEM 6--Safety iniection Slanal Reset l

At Millstone Unit No. 3, the Refueling Water Storage Tank (RWST) is the primary source of water for the Emergency Core Coolant System. The safety injection pumps take a normal suction from the RWST. No transfer to the RWST from any intermediate tank is required.

The action recommended by the NRC Staff concerning Safety injection Signal l Reset is not appropriate for Millstone Unit No. 3.

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r 1 9 o C-2 CATEGORY TUBES The current policy for eddy current testing (ECT) at Millstone Unit No. 3 requires that the inspection be performed according to the plant technical specifications at intervals which are at least as restrictive as the standard technical specifications (STS). The initial inspection sample size is 3 percent and the inspection is expanded, according to STS requirements, if test results indicate "C2" or "C3" category findings. This inspection policy has been found to be adequate to ensure steam generator (SG) tube integrity.

The additional tubes tested as a result of a "C-2" category are selected from problem areas, thus increasing the likelihood of identifying degraded tubes. If a degraded condition is widespread, it is highly probable that the STS method of expanding the test sample will, in fact, lead to a 100 percent test program. The effectiveness of this technique has been proven at Northeast Nuclear Energy Company in that past inspections that were expanded to "C-2" but not "C-3" have not led to excessive degradation over the subsequent cycle.

The need to inspect other SGs at the same unit is evaluated on a case-by-case basis. If a particular mode of tube degradation is identified and isolated to a single SG, then unnecessary, additional expense and radiation exposure is avolded by not expanding the inspection to other SGs.

The current ECT inspection policy has been found to be adequate to ensure SG tube integrity. The step-wise expansion of the sample size has been very ef fective in the monitoring of the condition of the tubes.

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