ML18052B453

Application for Amend to License DPR-20,revising Tech Specs to Delete Spec 3.18 Re Secondary Water Chemistry Limits & Replacing Spec W/Program Requirements in Administrative Section

ML18052B453
Person / Time
Site:	Palisades
Issue date:	01/19/1988
From:	Buckman F CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:
Shared Package
ML18052B451	List: ML18052B450 ML18052B453 ML18052B454 ML18052B456 ML18052B458
References
NUDOCS 8801250056
Download: ML18052B453 (6)

Text

CONSUMERS POWER COMPANY Docket 50-255 Request for Change to the Technical Specifications License DPR-20 For the reasons hereinafter set forth, it is requested that the Technical Specifications contained in the Provisional Operating License DPR-20, Docket 50-255, issued to Consumers Power Company on October 16, 1972, for the Palisades Plant be changed as described in Section I below:

I. Changes A. Delete Specification 3.18.

B. In Table 4.2.1, item 7, delete "pH and Specific Conductivity" and "Sodium" testing and frequency of testing.

(See page change revisions.)

C. Add new specification 6.22 as follows:

"6.22 SECONDARY WATER CHEMISTRY A program for monitoring of secondary water chemistry to inhibit steam generator tube degradation shall include:

1. Identification of a sampling schedule for the critical variables and control points for these variables,

2. Identification of the procedures used to measure the values of the critical variables,

3. Identification of process sampling points, which shall include monitoring the discharge of the condensate pumps for evidence of condenser in-leakage,

4. Procedures fot the recording and management of data,

5. Procedures defining corrective actions for all off-control point chemistry conditions, and

6. A procedure identifying (a) the authority responsible for the interpretation of the data, and (b) the sequence and timing of administrative events required to initiate corrective actions."

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II. Discussion The above proposed Technical Specifications changes are requested to align them with Standard Technical Specifications and to allow changes to the Secondary Water Chemistry that are within the proposed Technical Specifications administrative program.

The secondary water chemistry limits in present Technical Specification 3.18 and surveillance requirements in Table 4.2.1 are requested to be deleted since they no longer represent requirements that can best minimize further steam generator tube degradation. The present 3.18 requirements were approved, as Amendment 20, in 1976 and represented, at that time, the established 'limits, for all volatile treatment of secondary system. water to minimize tube degradation including that produced at the steam generator tube support plates, which has resulted in denting of steam generator tube. Denting is the most prevalent form of tube degradation in the Palisades steam generators.

Past steam generator tube eddy current profilimetry examinations, in 1981, 1983 and 1985, have indicated that denting mechanism continues to progress. Three tubes were plugged due to denting, dur.ing the present outage.

The tube denting is caused by production of magnitite in the tube and support plate crevice. The corrosion product, magnetite, is believed to result at Palisades from acidic chloride attack in the crevice. The reaction is accelerated by the presence of copper and oxygen. Magnetite occupies about twice the volume of the original carbon steel support plate and therefore expands against the tube wall. As the volume of the magnetite increases, it impinges inward on the tube wall and outward against the support plate. Both stress corrosion cracking of the tube wall and support plate cracking may occur.

In 1983 Palisades implemented a secondary water chemistry program which is based on EPRI published Steam Generator Owners Group "PWR Secondary Water Chemistry Guidelines". This program, which is contained in Palisades Plant Chemistry Operating Procedure COP-11, has action levels which are more conservative than the present Technical Specifications requirements. However, even with the implementation of these guidelines the denting of the steam generator tubes has continued.

Experience with the addition of boric acid to the secondary water, has shown it to arrest or slow the denting process *. Consumers Power has reviewed the application of boric acid to the secondary water, as has been promoted by NSSS vendors, and determined it will potentially improve steam generator reliability. The procedure guidelines are contained in Appendix A of the Steam Generator Owners Group EPRI publication, NP-270,4-SR.

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Boric acid tends to lower the pH of the entire con~ensate and f eedwater systems. Considering that a ma]ority of these systems are fabricated from f erritic materials which is similar to materials in all nuclear plants, it follows that increased corrosion rates and thus increased corrosion product transport would result. Actual field studies conducted at nuclear plants indicate that there was no apparent increase in corrosion product transport (EPRI NP-3278, Evaluation of Boric Acid in PWR Steam Generators; EPRI NP-3066, Implementation of Boric Acid in the Field - Indian Point Unit 3 Plant). Corrosion product transport studies were conducted at Palisades in 1985, 1986 and early 1987. With the addition of boric acid, these studies will be reinitiated. This data provides us with a very good baseline to determine if the addition of boric acid will increase corrosion product transport.

Westinghouse Standard Technical Specifications (STS) require that the plant shall have a program for monitoring of secondary water chemistry to inhibit steam generator tube degradation. Palisades Plant Chemistry Operating Procedure COP-11, Secondary System Chemistry, addresses the elements of the program defined by the STS and is derived from the EPRI PWR Secondary Water Chemistry Guidelines, Rev. 1, 1984. According to the STS the program shall include:

1. Identification of a sampling schedule for the critical variables and control points for the variables.

COP-11 (attached) includes tables for the different reactor power modes which describe the sampling schedule for critical variables. Also included as part of these tables are admini-strative limits for the variables.

2. Identification of ~he procedures used to measure the values of the critical variables.

The tables contained ~n COP-11 described above also include the analytical procedure to be used to measure the critical variable.

3. Identification of process sample points which shall include monitoring the discharge of the condensate pumps for evidence of condenser in-leakage.

Attachment 7 of COP-11 describes process sample points.

Section 4.3 of this attachment describes sampling for the condensate pump discharge. Section 4.7 describes how Palisades determines condenser in-leakage based on additional sampling.

4. Procedures for recording and management of data.

Chemistry Administrative Procedure CH 1.5, Chemistry Operating Logs, Records, Graphs and Data Management (referenced in COP-11), is the procedure which describes the controls placed on data pertinent to chemistry.

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5. Procedures defining corrective actions for all off-control point chemistry conditions.

Section 5.0 of COP-11 describes the normal control and corrective action measures to be taken when a specified parameter is outside the administrative control band.

6. A procedure identifying (a) the authority responsible for the interpretation of data and (b) the sequence of timing of administrative events required to initiate corrective action.

a. Responsible Authority:

Palisades Plant Administrative Procedure 4.20, Chemistry Department Organization and Responsibilities, states that "The Plant Chemist/Plant Chemical Engineer's responsibilities shall include .*.* Reviewing plant chemistry and operation data to discern possible trends toward degradation of any heat transfer equipment or abnormal changes in coolant system radioactivity."

b. Sequence and Timing of Administrative Events:

COP-11 is derived from the EPRI PWR Secondary Water Chemistry Guidelines and includes specific Action Levels that *'should be initiated and the timing of those events relative to the determination of an out-of-specification parameter.

Analysis of No Significant Hazards Consideration The changes to the secondary water chemistry with the addition of boric.

acid have potential effects on a steam generator tube rupture event,*

FSAR Section 14.15. Considerable laboratory testing has been conducted on Alloy 600 Inconel the Palisades Steam Generator type tubing with respect to methods of corrosion including the effect of boric acid on corrosion rate. One such laboratory test included the effect of boric acid on already initiated cracks. It was shown in this test that boric acid was effective both against crack initiation and crack propagation in a simulated S/G environment. (EPRI NP-5558, Boric Acid Application Guidelines for Intergranular Corrosion Inhibition.)

Denting,* associated with the corrosion of the tube support plate, can increase the probability of tube leakage. Lock-up of a tube in the tube support plate (ie, in its ability to move axially) and subsequent linear thermal expansion and contraction of the tube produces conditions that can result in the increased probability of tube leakage. Under certain circumstances such conditions could lead to tube rupture. It has been shown in both laboratory and field applications that the addition of TSOP0188-0012A-NL02

boric acid can mitigate, if not stop, tube support plate corrosion -(ie, denting), thus preventing additional tube lock-up and associated tube stresses. Therefore, the addition of boric acid does not increase the probability of a single tube rupture or the probability that more than one tube would rupture~

The effect of boric acid addition on other equipment important to safety has also been reviewed. Boric acid carry over to the turbine with possible detrimental effects on turbine blading, which could result in

.turbine missile production, have been evaluated in the industry.

Westinghouse (the Palisades turbine is a Westinghouse unit) was the first NSSS vendor to recommend boric acid addition. Laboratory tests indicate that boric acid carryover to the turbine is dependent upon moisture carryover. EPRI/Westinghouse sponsored research and development programs were conducted to evaluate the compatibility of boric acid with turbine materials. The results of the laboratory test program stated" **. no significant degradation of turbine materials is expected to occur due to the presence of boric acid" (EPRI NP-5558).

Furthermore, Westinghouse chemistry personnel conducted an evaluation of Secondary System Operations at Palisades (February 9, 1987 -

February 13, 1987) and provided a recommendation that Palisades should initiate boric acid secondary treatment. Other inhouse review has also concluded that there is no known evidence of degraded performance of secondary system valves.

Based on the above, it is concluded with the *addition of boric acid to.

the secondary water chemistry that there is no increase in the probability or consequences of an accident or malfunction of equipment (either the steam generator or turbine) important to safety. Therefore, the proposed changes to the Technical Specifications also do not increase the probability or consequences of an accident or malfunction of equipment. Changes to the Technical Specifications remove specific requirements for secondary water chemistry and replace them with a required administrative program that will allow the use of boric acid in the secondary system. Specific action levels to initiate plant derate,.

if the chemistry limits are not met, are encompassed in the administrative program which is consistent with Standard Technical Specifications.

The effect of the addition of boric acid to the secondary water and changes to the Technical Specifications will not create a different type of accident or malfunction of equipment. The effects of boric acid carryover to the turbine with possible detrimental effects on turbine blading, which could result in turbine missile production, have been eva~uated in the industry. Furthermore, the effect of boric acid on corrosion of materials in the Steam Generator, Feedwater System, and Turbine have been evaluated and no detrimental effects have been found in the laboratory or field use (EPRI NP-5558).

The margin of safety is not reduced. In fact, the addition of boric acid may increase the present margin of safety by mitigating the ongoing denting of the steam generator tubes. The present Technical TSOP0188-0012A-NL02

Specifications chemistry limits are provided to reduce the corrosive environment which had existed at the time of the change from phosphate to all volatile treatment (AVT). With the change to AVT the present administrative chemistry limits (which are more restrictive than the present Technical Specifications) were invoked to reduce wastage, pitting and the potential for further tube denting. The AVT by itself has not controlled the denting process. Industry experience, with boric acid addition, as endorsed by the NSSS vendors and the NRC, has shown the denting process to be mitigated in several PWR steam generators.

Therefore, the changes to the Technical Specifications and boric acid addition to the steam generators secondary water will not reduce the margin of safety defined in the basis of the Technical Specifications.

III. Conclusion The Palisades Plant Review Committee has reviewed this Technical Specification Change Request and has determined that this change does not involve an unreviewed safety question, and therefore, involves no significant hazards consideration. This change has also been reviewed under the cognizance of the Nuclear Safety Board. A copy of this Technical Specification Change Request has been sent to the State of Michigan official designated to receive such Amendments to the Operating License.

CONSUMERS POWER COMPANY Buckman, Senior Vice Energy Supply Sworn and subscribed to before me this 19th day of January 1988.

Bev~\:IAnn Avery~ Public Jackson County, Michigan My commission expires December 27, 1988

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