ML15112A975

Safety Evaluation Supporting Amends 88,88 & 85 to Licenses DPR-38,DPR-47 & DPR-55,respectively

ML15112A975
Person / Time
Site:	Oconee
Issue date:	11/07/1980
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML15112A974	List: ML15112A973 ML15112A975 ML15112A976
References
NUDOCS 8012020051
Download: ML15112A975 (9)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, 11, C. 20555 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO. 83 TO FACILITY OPERATING LICENSE NO. DPR-38 AMENDMENT NO. 88 TO FACILITY OPERATING LICENSE NO. DPR-47 AMENDMENT NO. 85 TO FACILITY OPERATING LICENSE NO. DPR-55 DUKE POWER COMPANY OCONEE NUCLEAR STATION, UNITS NOS. 1, 2 AND 3 DOCKETS NOS. 50-269, 50-270 AND 50-287 Introduction and Background By letters dated October 1, 1976 and July 8, 1977, as combined in a letter dated May 30, 1979, and as supplemented May 26, 1977, September 21, 1Q77 and June 11, 1979, the Duke Power Company (DPC or the licensee) proposed changes in Technical Specification (TS) 4.2-Reactor Coolant System Surveil lance. TS 4.2 is the Oconee Nuclear Station (ONS) Inservice Inspection (ISI)

Program. By letter dated March 24, 1980, DPC proposed a change to TS 4.3.2 regarding leak test pressure of the reactor coolant system (RCS).

The pro posed changes are designed to assure the Station is in compliance with 10 CFR 50.55a(g); in order to meet this Regulation, the ISI Program should be in compliance to the extent practicable with the 1974 Edition and Addenda through Summer 1975 of Section XI of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code. The ONS was designed and constructed prior to the implementation of the Code, and as a consequence, due to the system design, geometry, or materials of construction of the components, could not meet, in every case, the later Code requirements.

However, the Regulation and the Code provide for relief from these requirements if impractical.

Relief may be granted if acceptable alternate inspection requirements are proposed. Stated below are specific relief requests on a reactor unit by unit basis and our evaluation of each relief request. The licensee submittals of May 26, 1977, and September 21, 1977, constitute the relief requests specific to Units 1, 2 or 3; the June 11, 1979, submittal is a relief request common to all three units of the Station and is evaluated separately.

By letters dated January 18, 1978, for ONS Unit 1 and March 27, 1978, for Units 2 and 3, the NRC granted interim relief to all of the licensee's requests except the request in Duke's letter of June 11, 1979, which is evaluated herein. These interim reliefs permitted the three units to perform an ISI program that met the requirements of 10 CFR 50.55a(g) pending the completion of our detailed review as provided by this Safety Evaluation.

0 120 067

Eval uation

-2 I. CLASS 1 COMPONENTS A. Reactor Vessel

1. Relief Request Relief from reactor pressure vessel nozzle inspection (Category B-D) as required by paragraph IWB-2411 is requested for ONS Units 1, 2 and 3.

Code Requirement At least 4 of 8 nozzles" must be inspected by completion of 80 months of operation.

Licensee Basis for Requesting Relief The net effect of the above Code requirements is that four nozzles of a total of eight must be examined by the end of the 80 months of commercial operation. Due to core support structure design only the two reactor coolant outlet nozzles are accessible without removing the core barrel, which in turn requires complete defueling. This requirement is considered to be impractical. In lieu of the above, the following examination sequence is proposed:

Examinations Schedule (Elapsed Time Since Components to be Examined Commercial Service Date) 1 1

Reactor Coolant Outlet Nozzle Approximately 40 months 1

Reactor Coolant Outlet Nozzle Approximately 80 months 4

Reactor Coolant Inlet Nozzles Approximately 120 months 2

Core Flooding Nozzles Approximately 120 months Different nozzle will be examined each inspection period.

Eval uation Examination of the nozzles in the sequence required by the Code places an undue burden on the licensee because examination of the reactor coolant inlet and core flooding nozzles can only be accomplished by removing the fuel and core barrel from the. reactor vessel.

Examination of the outlet nozzles as proposed by the licensee will constitute a representative sample of the condition of the remaining nozzles because of similar service conditions. If any unacceptable flaw is found during an examination of the outlet nozzles, the examination will have to be extended to include additional nozzles as required by the Code.

-3 We find the proposed sequence for examination of the nozzles acceptable, will provide assurance of their structural integrity, and will not significantly decrease the safety of the facility.

We conclude that relief from the Code requirement may be granted as compensated for by the licensee's proposed schedule.

2. Relief Request Relief from the requirements of Table IWB-2500 Category B-I-i and paragraph IWB-2411 for the reactor vessel clad patch examination is requested for ONS Units 1, 2 and 3.

Code Requirement Except as specified by IWB-2500 for examinations that may be deferred to the end of the inspection interval, at least 25% of the required examination shall be completed by the expiration of one-third of the inspection interval and at least 50% shall be completed by the expira tion of two-thirds of the inspection interval.

Licensee Basis for Reg esting Relief Performance of these examinations requires complete defueling of the core and removal of core barrel.

Evaluation The licensee has proposed to inspect 100% of the required cladding patches at the end of'the inspection interval. The inspection sequence does not comply exactly to Code requirements. The licensee s examination of the reactor vessel outlel nozzles will cover sufficient area of the cladding to indicate the cladding general condition. We conclude that the safety gained by the Code inspection sequence requirements exactly is not commensurate with the burden placed upon the licensee. We conclude that the proposed inspection sequence is acceptable and relief from Code requirements for the reactor vessel cladding insrection sequence may be granted.

B. Piping Pressure Boundary

1. Relief Request Relief from the requirements of Table IWB-2600, Item 4.9 Category B-k-1 is requested for:

Oconee Unit No. 1 Low Pressure Injection and Core Flooding Systems' Welds Nos. 46LA and 6OLB.

Oconee Unit No. 2 Core Flood Tank and Decay Heat Removal Systems' Welds Nos. 53A and 102A and High Pressure Injection System Welds 932 and 89C.

g

-4 Code Requirement The welds of external support attachments to the pressure retain ing boundary including the base metal beneath the weld zone and along the support member for a distance of two support thicknesses shall be volumetrically examined.

Licensee Basis for Requesting Relief The weld geometry of the attachment welds prevents meaningful volu metric examination.

Evaluation Because of the weld design, a meaningful ultrasonic examination cannot be accomplished.

Radiographic examination of these welds would be difficult to perform and interpret, and would therefore result in little added assurance to safety. The licensee has committed to subject these welds to sur face examination. Based on the loading conditions of these types of welds, flaws would most likely generate at the weld surface and thus be detectable by surface examination.

We requested that the licensee also perform an ultrasonic examination of the base metal in order to assure that flaws in the base metal do not exist. The licensee agreed to perform this added examination.

The combination of surface examination and recommended volumetric base metal exam would provide assurance that the integrity of the pipe supports would be maintained.

II. CLASS 2 COMPONENTS

1. Relief Request Relief is requested from system pressure tests for ONS Unit 1 Main Steam SystemWeld No' 50 which is to be replaced by a 1.inch socket weld on the inlet side of a manually operated steam drive valve.

Code Requirement IWA-4210, P essure Test, requires that after repair by welding on the pressure re"aining boundary of components, a pressure test shall be performed in accordance with the requirements of IWA-5000 and IWC-5000 for Class 2 weld.

Licensee Basis for Requestino Relief The weld in question is not directly on, the main steam header.

Hydrostatic testing of the weld would require pressurizing the steam generato secondary side, maiin stean lines and sections of the feecwater header., It would also' require heatup of the steam generator and involve operation of many related systems.

It is estimated that 7-8 oays of down time would be required to perform this hydro. Additionally, the potential for damage to the main steam system is higo since it is not de'signed to be filled with water. With one weld involved, it is felt that a system leak test

5 at operating conditions is as reliable as hydrostatic test to assure leak tightness. In addition, an examination using the liquid dye penetrant technique along with ultrasonic testing will be performed.

Evaluation From the piping diagrams, it is clear that the licensee would have to pressurize the connected systems in order to hydrotest this repaired weld. The licensee,7has proposed an inservice leak test at operating pressure and temperature in addition to the surface and volumetric examinations to be performed. Considering-the one inch nominal pipe size system with which this weld is associated, we believe that the proposed alternative testing will ensure the integrity of the weld and this relief request may be granted. However, it is noted that the hydrotest required by the Code during each inspection interval is in no way waived by the granting of this relief request.

2. Rel ief Request Relief from hydrotesting the decay heat removal cooler outlet control valves LP-12 and LP-14 to 125% of design pressure after valve replace ment is requested for ONS Units 1, 2 and 3. The licensee proposes instead to test the valve to 100% of design pressure on upstream and downstream sides and conduct radiography of 100% of the valve joint welds..

Code Requirement The system hyrostat ic test pressure shall be at least 1.25 times the system design pressure.

Licensee Basis for Requesting Relief The decay heat removal coolers are located upstream of these valves.

The piping between the coolers and the valves is designed for 350 psig at 3000F. The valves are not leak tight, having design leakage of 0.5%

and being normallylused to control flow, not for isolation purposes. The piping downstream of the valves is designed for 505 psig at 2500F. Upon replacement of these valves, the welded joints were required to be hydro statically tested to 125% of design pressure. Even the piping downstream of the valves would be tested to normal operating pressure add with leakage through the valves, the piping with lesser design pressure as well as the coolers could become overpressurized and possibly damaged.

Venting of the upstream piping to relieve the pressure buildup could release significant amounts of high activity waste and prevent satis factory completionlof the hydrostatic test.

Eval uation The circumstances which surround this particular test clearly prevent weld isolation such that the Code required pressure can be used in per forming this test. The alternative testing proposed will assure, with the supplemental radiographic techniques, that any flaws.developed during

-6 repair or service will be found. Additionally the weld will be hydrostatically tested to 100% of design pressure and thus will provide reasonable assurance that large flaws will be detected.

We find that the basis for this request is reasonable and that relief from hydrotesting the repair welds to 125%,.of design pressure may be granted.

III.

CLASS 3 COMPONENTS

1. Relief Request, Relief from pressure testing to 1.10 times the design pressure the reactor coolant pump seal supply line is requested for ONS.Unit 1.

This line contains welds 1K and 1L which are new welds installed during a Station modification performed during the 1977 shutdown.

Code Requirement Visual examination shall be conducted for evidence of component leakage, structural distress, or corrosion when the system is.under going a system pressure test. The system test pressure shall be at Teast 1.10 times the system design pressure.

Licensee Basis for Requesting Relief The design pressure for this system is 3050 psig. In order to meet the requirements of the Code, the test pressure must be 3355 psig.

The test pressure exceeds that pressure allowed wjth fuel in the vessel.

The new welds,,1K and IL, were radiographed and found acceptable.during the 1977 refueling shUtdown.

Eval uation The design of the reactor coolant pump seal supply line prevents isola tion of the seal supply line for pressure testing at a pressure speci fied by the Code. The repair welds have been radiographed and found acceptable. In addition, we requested that the seal supply line be visually examined during a hydrostatic test at 100% of system pressure.

DPC agreed to include these two welds in the hydrotest program. We believe that the combination of radiography and recommended pressure testing will provide adequate assurance of system integrity and this request may be granted.

IV. GENERAL

1. Relief Request Relief from the rules of ASME Section XI IWA-2120 regarding the Author ized Nuclear Inspectors witnessing or auditing test results is requested for ONS Units 1, 2 and 3.

-7 Code Requirement IWA-2130(b) states that any inspector who performs inspections required by this Division shall have first been qualified by written examination pursuant to the legislation of rules of a state of the United States, the legislation of a Canadian Province, or the ruTes of another authority having jurisdiction over a nuclear power plant at the installation location and that has adopted this Division. The Inspector shall not be an employee of the owner or his agent.

Licensee Basis for Requesting Relief The duties of the Authorized Inspector as stated in ASME Code Section XI, IWA-2120, are performed to the full extent by personnel within the Quality Assurance Department. This department of DPC is organizationally separate from those persons, responsible for performing engineering, construction, or operating functions. The personnel within the Quality Assurance Department have the required independence and authority to effectively carry out the quality assurance program without undue influence from those directly responsible for costs and schedules.

Eval uation IWA-2130(b) states specifically that the Inspector 'Shall not be an employee of the owner or his agent. It is concluded that the licensee should meet the requirements of the Code concerning the Authorized Nuclear Inspector. The purpose of the requirement is to,have an inde pendent third party as the Inspector. The issue was discussed with DPC and they agreed that an independent third party Inspector will be used.

2. Relief Request Relief from.the holding time requirement for system hydrostatic and leak tests (IWA-5210) is requested for ONS Units 1, 2 and 3.

Code Requirement The pressure-retaining components shall be visually examined while the system is under the hydrostatic test pressure and temperature.

The test pressure and temperature shall be maintained for at least four hours prior to the

.performance bf the examinations.

Licensee Basis for Requesti q Relief The approved Code -

1974 Edition including throuph Summer 197.5 Addenda contains in SectionXI,-Article IW,-5000, System Pressure Test, the recuire ment to perform a hydrostatic test "for at least four hours prior to tie performance of the examinations" (IWA-5210(a)).

The performance of this test is impractical particularly in situations where boundary valves used to isolate piping sections for this test are not designed for zero leakage and leak by the seats at a-rate greater than the capacity of the hydrostatic pump. In addition,, it is not necessary to wait four hours to observe leakage of a welded joint. Any weidment lakage would be readily observable within a matter of minutes.

-8 In a later edition of the Code - 1977 Edition including through Summer 1978 Addenda - the hydrostatic test requirements are stated for conditions of insulated and noninsulated piping. The four-hour hydrostatic test is required only for insulated.systems while only 10 minutes is required for a noninsulated piping system. However, this edition of the Code is not currently approved by the NRC.

It is the position of DPC that this later edition of the Code clarifies the previous edition of the Code with respect to the four-hour hydro static test and is applicable in cases where hydrostatic testing is required.

Evaluation The four-hour 'holding time required by the 1974 Edition of Section XI during hydrostatic tests i~s intended for application to systems where the base material and sweld deposits are covered by insulation.

The purpose of the holding time is to allow pressure boundary leakage to become evident at the insulation surface.

Where the base material and weld are visible, the Intent of the holding time is meaningless and deletion of this requirement wfll not decrease the effectiveness of the examination.

We conclude that this request -may 'be granted with the following condi tions, Which 'have been discussed with and agreed to by DPC:

a) When,performing a system pressure test the entire system must be visible directly. This includes the welds and all base materials.

b) When the ;areas are exposed, the pressure and temperature required by the Code for the hydrostatic and leak.test shall be maintained for a minimum time of ten (10) minutes and for such additional time as may be necessary to conduct the examinations.

c) Following a repair, the repaired area must be accessible for a direct visual examination.

Conclusions on Relief Requests and ISI Program We find that the proposed Technical Specification changes are acceptable in that they meet the requirements of 10 CFR 50.55. The licensee has submitted infor mation to support his determinations that certain ASME Section XI Code (1974 Edition through Summer 1975) requirements are impractical to implement at ONS.

We have evaluated the licensee's bases for his determinations and find that relief from the specific Code requirements requested may be granted except for using a DPC employee in the position of an Authorized Nuclear Inspector. We conclude that the revised ISI Program meets the requirements of 10 CFR 50.55a(g).

V. LEAK TEST PRESSURE FOLLOWING OPENING OF REACTOR COOLANT SYSTEM (RCS)

By letter dated March 24, 1980, DPC requested that the leak testing pressure following any opening of the RCS be reduced from 2285 psig to 2200 psig.

Section XI of the ASME Code in Paragraph IWB-5221 requires that the system leak test pressure be no less than the system nominal operating pressure at 100% rated reactor power. The Final Safety Analysis Report states that the nominal operating pressure is 2150 psig; we have verified that all three ONS units currently (1980) operate al 2150 psig. As the requested leak test

-9 pressure of 2200 psig is greater than the Code minimum of 2150 psig, we conclude the change is acceptable.

Environmental Consideration We have determined that this action does not authorize a change in effluent types or total amounts nor an increase in power level and will not result in any significant environmental impact.

Having made this determination, we have further concluded that this is an action which is insignificant from the standpoint of environmental impact and, pursuant to 10 CFR §51.5(d)(4), that an environmental impact statement, or negative declaration and environmental impact appraisal need not be prepared in connection with this action.

Conclusion We have concluded, based on'the considerations discussed above, that:

(1) because this action does not involve a significant increase in the probability or consequences of accidents previously considered and does not involve a significant decrease in a safety margin, the action does not involve a significant hazards consideration, (2) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (3) such activities will be conducted in compliance with the Commission's regulations and the issuance of this action will not be inimical to the common defense and security or to the health and safety of the public.

Dated: November 7, 1980