ML19347F531

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Testimony of Mf Alesky Re Doherty Contention 50,jet Pump Beams.Prof Qualifications Encl.Related Correspondence
ML19347F531
Person / Time
Site: Allens Creek File:Houston Lighting and Power Company icon.png
Issue date: 05/11/1981
From: Alesky M
GENERAL ELECTRIC CO.
To:
Shared Package
ML19347F516 List:
References
NUDOCS 8105190543
Download: ML19347F531 (7)
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Text

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( // Docwed 5 1 UNITED STATES OF AMERICA WC 3 NUCLEAR REGULATORY COMMISSION ~

2 BEFORE THE ATOMIC SAFETY AND LICENSING BOARp-

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4 In the Matter of )

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5 HOUSTON LIGHTING & POWER COMPANY) Docket No. 50-466

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6 (Allens Creek Nuclear Generating)

Station, Unit No. 1) )

7 )

8 TESTIMONY OF MICHAEL F, ALEKSEY ON BEHALF OF HOUSTON LIGHTING & POWER CO. ON DOHERTY CONTENTION 50 9, JET PUMP BEAMS i

10' O. Please state your name and place of employment.

11 A. My name is Michael F. Aleksey Lnd I am employed by General 12 Electric Company as a Senior Design Engineer in the Reactor 13 and Containment Design Section. My business address is 175 14 Curtner Avenue, San Jose, California.

15 Q. Please describe your professional qualifications.

16 A. My professional qualifications are set forth in Exhibit 17 MFA-1 to this testimony.

18 Q. What is the purpose of your testimony?

19 A. The purpose of my testimony is to address Mr. Doherty's 20 Contention 50, which says:

21 Applicant's jet pumps in the coolant circulation system of the proposed ACNGS will be subject to 22 disassembly, End/cir hazardous displacement resulting in coolant circuletion degradation during operation 28 leading to reduction of the margin of safety during normal operation or design basis accidents (DbA),

24 due to cracking in reactor internal parts for holding the jet pumps in place and the jet pump itself.

26 Q. What is your understanding of the real conceri. expressed 27 in this contention?

28. A. My understanding of Mr. Doherty'c concern is that if 810519037tg3

4 1- 2l. the jet pump beam, which is holding the jet pumps in place, 3l cracks or if the jet pump cracks, the coolant recircula-4 tion system will be subject to disassembly, and/or hazardous displacement. This will result in coolant circulation 5l degradation during operation leading to reduction of the 6L 7 margin of safety during normal operations or during a 8 design basis accident (DBA).

9' O. What is the function of the jet pump?

10 A. During normal reactor operation, the function of the 11 jet pump is to develop the required driving head to the 12 primary coolant for the purpose of circulating the coolant 13 through the reactor core. A secondary function of the 14 jet pump is to provide core flow measurements through 15 calibrated diffusers. Each jet pump consists of an inlet 16 m4.xer, a diffuser, and a central riser commen to two jet 17 pumps. There are a total of 20 jet pumps located in the 18 annular region between the core shroud and the vessel inner 19 wall.

20 The jet pumps also have a safety function during the 21 design basis Loss-of-Coolant-Accident (LOCA). For the 22 LOCA event, the jet pumps allow post-accident flooding of 23 the core to no less than two-thirds of the core height.

24 This feature assures that a high enough level of water will 25 remain on the core such that along with Emergency Core 20 Cooling Systems the core will remain within 10 CFR 50 27 Appendix K limits.

28 Q. Hcw are the jet pumps held in place?

t 1 2 A. The jet pump risers are welded to the reactor recircula-3 tion inlet safe end thermal sleeve; its upper end is also 4 welded directly to the vessel wall by means of a riser 5 brace. The diffusers are anchored to the vessel shroud support ledge also by welding. The inlet-mixers connect 6l between the risers and diffusers are held in place by pre-7 8; loaded beam-bolt assemblies. The inlet-mixers as well 9 as the beam-bolt assemblies are designed as removable and 10l replaceable units.

11 Q. Have any BWR's experienced jet pump beam cracking?

12 A. Through the end of March 1981, cracking of one or 13 more jet pump beams has been observed in Dresden Unit 3, 14 and in nine of the other 26 BWR's examined. Metallurgical 15 examination of the failed Dresden beam and subsequent 16 cracked beams revealed the fracture surface to be totally 17 intergranular.

18 General Electric has summarized the results of their 19 investigations as follows: The cause of crack initiation 20 and failure of all beams evaluated has been Intergranular 21 Stress Corrosion Cracking (IGSCC). IGSCC is the cracking 22 of metals along their grain boundaries and is caused by 23 a combination of relatively high stress, a corrosive environ-24 ment and a physical characteristic of the metal which renders 25 grain boundary legions of the waterial susceptible to local 26 corrosive attack.

27 Q. Have any BWP's experienced cracking in the jet pump 28 themselves?

1 2

, A. To date, no IGSCC has been discovered in the jet pumps 3 themselves. They are made almost entirely of 304 stainless 4 steel and Alloy 600, and are subjected to sustained stress 5 levels significantly telow the sustained stress in the beam.

6 Consequently, IGSCC in the jet pump is not expected.

7 Q. What changes have been made in the physical design g features of the Allens Creek holddown beams to reduce 9 stress levels?

10 A. The jet pump beams at ACNGS will be larger than the 11 beams used at Dresden 3. The Dresden 3 beams are 2 inches 12 high, 10.5 inches long, and 3.26 inches wide. The ACNGS

. beams will be 2.3 inches high, 10.5 inches long, and 3.3 13 14 inches wide.

15 O. What is being done to correct this cracking problem 16 in the jet pump beams and what will be done to ensure that 17 if a crack is discovered, no degradation of the system 18 operation will exist?

19 A. General Electric has determined that by changing the 20 heat treatment of the metal, Alloy X750, and reducing the 21 stresses imposed on the beam, the potential for jet pump 22 beam cracking is substantially reduced.

23 The physical characteristics of the material will be 24 changed by modification of t?e heat treatment of the beam.

25 Heat treating of metal is done to ensure that the desired l 26 grain structure and grain boundary composition is formed 27 in the metal. The original heat treatment, used on the jet 28 pump beams which experienced cracking, was to heat the

1 2 material to 1625'F and hold it there for 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, then 8 subsequently heat it to 1300'F and hold it there for 20 4 hours. The heat treatment to be used on the newer beams will be to heat the material to approximately 2000'F for 5l 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> and subsequently heat it to 1300'F and hold it 61 b

7' there for 20 hours2.314815e-4 days <br />0.00556 hours <br />3.306878e-5 weeks <br />7.61e-6 months <br />. This new heat treatment will strengthen 8 the grain boundaries and lessen susceptibility to IGSCC.

9l This cin be done because the new heat treatment, high 10 temperature annealing, softens the metal and produces a 11 recrystallized grain structure. This grain structure is 12 less susceptible to IGSCC and when it is then age hardened 13 at 1300,aF for 20 hours2.314815e-4 days <br />0.00556 hours <br />3.306878e-5 weeks <br />7.61e-6 months <br />, the metal attains its final required a 14 hardness (strength) with the improved grain structure.

15 The stress in the BWR/6 jet pump beam is lower than 1E in a BWR/3 due to the larger beam size as described pre-17 viously. Also, in response to the cracking problem, General 18 Electric has further reduced the stresses in the beam by 19 reducing the beam preload. Thus, changes result in a 20 sustained stress reduction of from approximately 06,000 psi 21 to 63,000 psi.

22 In addition to the actions described above, the NRC >

23 has a program to perform surveillance of the jet pumps 24 which will enable the operator to ensure that the jet pumps i

25 are performing as designed. This surveillance program is 26 described in Inspection and Enforcement Bulletin 80-07.

27 All operating plants are requirea to meet these require-20 ments Os an interim fix. HL&P will commit to a surveillance

1 2 program at the operating license stage as part of the 8 Allens Creek Technical Specifications which will reflect 4 requirements in effect at that time.

5 A program also exists t>nareby the jet pump beams 6 can be ultrasonically inspected while installed in the 7 vessel. This is a procedure using equipnent and techniques 8 developed by General Electric. This program will give 9 operational verification of the beam integrity. HL&P 10 will perform any required 1. service inspection.

11 Q. What are your conclusions?

12 A. The reduced sustained stress levels and the high 13 temperature annealing heat treatment reduce the likelihood 14 of IGSCC which has been identified as the cause of the 15 jet pump beam cracking.

16 17 18 19 20 21 22 23 24 25 26 ,

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e 1  ; Exhibit MFA-1 2 EDUC."sTION AND PROFESSIONAL QUALIFICATf0NS 3 Michael F. Aleksey 4 Mr. Aleksey is a Senior Design Engineer in the Reactor 5 and Containment Design Section of the General Electric 6 Company, Nuclear Power Systems Engineering Department, in 7 San Jose.

8' His cmploy..~nt with General Electric began in 1972 as 9 an engineer in the Reactor Equipment Design Unit. In 10 this capacity, he was responsible for testing and evaluation 11 of various reactor internal components. In 1974, Mr. Aleksey 12 transferred to the Wilmington, North Carolina, manufacturing 13 facility where he was the Resident Design Engineer for various 14 componento including the jet pumps. In 1977, he returned to 15 San Jose where he assumed responsibility for an improved 16 feedwater sparger design. He subsequently received the General 17 Manager's recognition in connection with various design 18 activities associated with the feedwater sparger program. In 19 1979, he assumed design responsibility for the jet pump 20 design. Since 1980, Mr. Aleksey also acted as Program Manager 21 of the Reactor Pressure Vessel (RPV) Surveillance Sample 22 Program and has responsibility for the planning, scheduling, 23 budgeting and implementation of the GE BWR PRV Surveillance 24 Eample Design.

Mr. Aleksey is a 1971 graduate of Washington State 20l University with a BS Degree in Mechanical Engineering.

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