ML20154R846

Forwards Revised 880125 Inservice Insp Relief Request for Second 10-yr Insp Interval.Util Agrees to Revise Proposed Alternative Category B-L-1 & B-L-2 Exams of One Unit 1 & One Unit 2 Reactor Coolant Pump Casings,Per 880414 Suggestions

ML20154R846
Person / Time
Site:	Point Beach
Issue date:	05/31/1988
From:	Fay C WISCONSIN ELECTRIC POWER CO.
To:	Wagner D NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM), Office of Nuclear Reactor Regulation
References
CON-NRC-88-050, CON-NRC-88-50 VPNPD-88-308, NUDOCS 8806080215
Download: ML20154R846 (15)

Text

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Wisconsin Electnc eaara covess, 231 W. MICHIG AN.P.O BOX 2046, MILWAUKEE.WI 53201 (414)221 2345 VPNPD-88-308 NRC-88-050 May 31, 1988 U. S. NUCLEAR REGULATORY COMMISSION Document Control Desk Mail Station Pl-137 Washington, D.C. 20555 Attention: Mr. David Wagner, Project Manacer Project Directorate III-3 Gentlemen:

DOCKETS 50-266 and 50-301  !

ASME SECTION XI, RELIEF REQUESTS POINT BEACH NUCLEAR PLANT, UNITS 1 and 2 j In a letter to the NRC dated Januav:y 25, 1988, Wisconsin Electric Power Company requested nn inservice inspection relief for the second ten-year inspectica interval for the Point Beach Nuclear Plant, Units 1 and 2. The request was for relief from the requirement to conduct Category B-L-1 and B-L-2 examinations on one Unit 1 and one Unit 2 reactor coolant pump casing.

I In a response to Wisconsin Electric dated April 14, 1988, the NRC staff indicated our proposed alternative examinations would be generally acceptable and suggested several additions regarding the alternative examinations. We have reviewed the suggestions from your April 14, 1988 letter and agree to revise our proposed alternative examinations as follows:

(a) A visual (VT-2) examination of the casing exterior will be performed in conjunction with the system leakage test every outage and each system hydrostatic test.

(b) If maintenance or operational problems are encountered which necessitate disassembly of the casing internals of either pump, a VT-1 examination of the interior casing surface will be performed. If a pump is not disassembled, this commitment will extend to the next inspection interval.

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8806080215 880531 PDR ADOCK 05000266 0t DCD

U. S. Nuclear Pegulatory Commission May 31, 1988 Page 2 (c) If a pump is disassembled to the extent that a radiographic examination is practical and a miniature linear accelerator (MINAC) is available, the code-required volumetric examination will be performed.

(d) Once each interval, an exterior surface examination of approximately one-third of the accessible pump casing weld surface will be conducted in conjunction with a 100% exterior visual examination (VT-1). If the code-required examination is performed as discussed in Item (c) above, this examination is not necessary.

(e) Vibration monitors are currently installed on the motor frame near the lower radial bearing and on the motor shaft above the pump casing. These monitors will alarm on panel C04 in the control room if either detects high vibration. The PBNP Operating Procedures Manual provides reacror coolant pump (RCP) vibration limits.

If the limits are exceeded, we would expect to shut down and determine the cause. These monitors would most likely detect any problem which could lead to pump casing, welds, or rotating element failure.

Your letter also asked us to describe any previous attempts to perform ultrasonic testing on the reactor coolant pump casing welds at Point Beach. To date, we have not attempted any ultrasonic examinations of the reactor coolant pump casing welds. We believe that ultrasonic testing of the welds is impractical. This is based both on our past experience with UT on other stainless steel castings and on past industry experience. However, because the NRC staff considers the impracticality of ultrasonic testing to be plant specific we will attempt ultrasonic testing on one weld of a Unit I reactor coolant pump during the spring 1989 refueling outage. Should it prove to be a practical method for volumetric examination of the casing welds, we would propose to complete the ASME Section XI category B-L-1 examination using the ultrasonic method on both Unit 1 and Unit 2. However, in that our testing may very well demonst:' ate that ultrasonic testing will be impractical, we request that the attached relief requests be approved.

I U. S. Nuclear Regulatory Commission May 31, 1988 Page 3 We believe that these revised relief requests enclosed herewith address your concerns. If you have any further questions, please contact us.

I Very truly yours,

?

hU Qi :

C. W. Fai Vice President Nuclear Power Enclosures Copy to NRC Regional Administrator, Region III NRC Resident Inspector

ATTACliMENT 1 UNIT 1 RELIEP REQUEST Relief Request No. RR-1-13 (Revision 1)

Description:

Reactor Coolant Pump Casing Wolds

4 ATTACHMENT 1 Component Reactor Coolant Pump Exam Area .

Class 1 Casing Welds l l

Isometric or Component Drawing '

See Attachments 3 and 4 i ASME Section XI Category B-L-1 B-L-2

ASME Section XI Item Number B12.10 B12.20 l

) ASME Section XI Examination Requirement l j

i B-L-1: "The exami ations performed during each inspection i interval snall include 100% of the pressure-retaining  ;

welds in at least one pump in each group of pumps '

performing similar functions in system (e.g.

recirculating coolant pumps)." The exam method shall be volumetric.

B-L-2: "One pump in each of the group of pumps performing similar functions in the system shall be examined during each inspection interval. This examination may be performed on the same pump selected for the category B-L-1 examination." The exam method shall be visual.

]

Alternative Examination A visual (VT-2) examination of the casing exterior will be performed in conjunction with the system leakage test every outage and each system hydrostatic test.

1 i

If maintenance or operational problems are encountered which necessitate disassembly of the casing internals of either pump, a VT-1 examination of the interior casing surface will be performed. If a pump is not disassembled, this commitment will extend to the next inspection interval.

If a pump is disassembled to the extent that a radiographic examination is practical and a miniature linear accelerator (MINAC) is available, the code-required volumetric examination will be parformed.

Once each interval, an exterior surface examination of approximately one-third of the accessible pump casing weld surface will be conducted in conjunction with a 100% exterior visual examination (VT-1). If the code-required examination is performed as discussed above, this examination is not necessary.

Reason for Relief Request The two reactor coolant pumps (RCP) for Point Beach Unit 1 are Westinghouse Model 93 pumps. Each pump casing is fabricated by welding four stainless steel (SA351 CF8) castings together.

Thus, there are three circumferential pressure-retaining welds that are to be volumetrically inspected in accordance with Category B-L-1. Because the physical properties of the stainless steel castings and weld material prevent meaningful ultrasonic examination, the casing welds must te inspected using the miniature linear accelerator (MINAC).

l This radiographic examination is performed by placing the MINAC l inside the pump casing and placing the film on the outside of the pump. To perform the examination, the pumps must be completely disassembled. Disassembly to this extent is far l beyond any disassembly expected except for this examination. j Also, insulation on the casing exterior must be removed for film '

nlacement. Additionally, the pump bowl must be dry for installation of the MINAC. Therefore, all fuel assemblies must be removed from the reactor vessel and the vessel water level i lowered to below the nozzles. Complete disassembly of the pump is also required to conduct the VT-1 examination in accordance with Category B-L-2.

This radiographic examination using the MINAC was performed on Point Beach Unit 1 "B" RCP during the Fall 1981 refueling outage. In addition, the same examination has been performed at several other sites. No problems have been found with the welds at any site. Additionally, no problems have been found during the Category B-L-2 visual examination. This visual examination was conducted at PBNP by using the video camera on the MINAC.

We believe that performing a volumetric examination of the Point Beach Unit I reactor coolant pt...p casing welds and a visual examination of the interior pressure retaining surface of one pump during the second ten year inspection period does not 2-

provide an increase in safety commensurate with the associated cost potential for inadvertent pump damage, and expected radiation exposure. The following items have been considered:

1. Radiation Levels Currently the average does rates at the RCP are:

8' elevation general area < 1 - 25 mR/hr Below RCP 10 - 800 mR/hr in RCP 700 - 10,000 mR/hr

2. Total Estimated Exposure During The Examination The whole body doses received during the fall 1981 examination of Unit 1, RCP-B are listed below. This list does not include the additional dose received while getting the plant to a condition whero RCP disassembly could be performed (e.g., complete core unload).

- PBNP maintenance personnel during disassembly 5,237 mR

- Contractor personnel - diffuser adaptor removal 3,890 mR

- Contractor examination personnel 12,626 mR

- Contractor personnel - insulation 4,490 mR removal / replacement

- Contractor personnel - diffuser adapter 1,833 mR replacement

- PBNP Maintenance personnel - reassembly 6,017 mR TOTAL 34,093 mR

3. Pump Disassembly The Category B-L-1 and B-L-2 examinations require complete disassembly of the pump. The pump manufacturer (Westinghouse) does not require or recommend pump

, disassembly to perform normal maintenance or inspections.

The only time disassembly to this degree has ever occurred was to perform this examination during the fall of 1981.

Therefore, very limited experience in this area may result in significant damage or degradation to the pump.

Additionally, complete pump disassembly is not anticipated for any other reason in the foreseeable future.

4. Pump Performance The type of material used in these pumps is widely used throughout the industry and has performed very well. There have been no reported problems or failures with the casing welds of these model pumps. Additionally, the licensee has had no operational problems with the RCPs which could indicate potential degradation of the casing welds.

5. Excessive Cost  !

The estimated cost to disassemble / reassemble the pump, remove and reinstall insulation and to perform the '

examination is approximately $810,000. Additionally, this examination is expected to extend the refueling outage a minimum of 5 days. Therefore, replacement power costs would be a minimum of about $1.5 million. Any minor problems which might occur could significantly increase the cost of the examination.

6. Alternative Examinations The alternative examinations we are proposing, as well as the already installed vibration monitoring system, will be sufficient to detect any problems which may occur.

(a) A visual (VT-2) examination of the casing exterior will be performed in conjunction with the system leakage test every outage and each system hydrostatic test.

(b) If maintenance or operational problems are encountered which necessitate disassembly of the casing internals of i either pump, a VT-1 examination of the interior casing l surface will be performed. If a pump is not l disassembled, this commitment will extend to the next l inspection interval.

(c) If a pump is disassembled to the extent that a

, radiograph examination is practical and a minature i

linear accelerator (MINAC) is available, the code-required volumetric examination will be performed.

l (d) Once each interval, an exterior surface examination of approximately one-third of the accessible pump casing weld surface will be conducted in conjunction with a 100% exterior visual examination (VT-1). If the l code-required examination is performed as discussed in Item (c) above, this examination is not necessary.

(e) Vibration monitors are currently installed on the motor i frame near the lower radial bearing and on the motor shaft above the pump casing. These monitors will alarm on panel Co4 in the control room if either detects high vibration. The PBNP Operating Procedures Manual provides reactor coolant pump vibration limits. If the limits are exceeded, we would expect to shut down and i determine the cause. These monitors would most likely l detect any problem which could lead to pump casing,  ;

welds, or rotating element failure. l l l l

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j l

4-J

In conclusion, we believe that, based on the preceding items, performing the volumetric inspection of the RCP casing welds and the visual examination of the internal surface of the pump casing during the second ten-year interval do not provide a commensurate increase in safety. We, therefore, request approval of this relief request.

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ATTACllMENT 2 UNIT 2 RELIEF REQUEST Relief Request No. RR-2-13 (Revision 1)

Description:

Reactor Coolant Pump Casing Wolds 1

l l

l l

l

ATTACHMENT 2 Component .

Reactor Coolant Pump

, Exam Area Class 1 Casing Welds Isometric or Component Drawing See Attachment ASME Section XI Category B-L-1 B-L-2 t i

ASME Section XI Item Number 6 B12.10 l B12.20 i i

d ASME Section XI Examination Requirement B-L '.: "The examinations performed during each inspection interval shall include 100% of the pressure-retaining

welds in at least one pump in each group of pumps i

performing similar functions in system (e.g.

recirculating coolant pumps)." The exam method shall be volumetric.

q B-L-2: "One pump in each of the group of pumps performing similar functions in the system shall be examined during each inspection interval. This examination may be performed on the same pump selected for the category i B-L-1 examination." The exam method shall be visual. l i

Alternative Examination i A visual (VT-2) examination of the casing exterior will be i performed in conjunction with the system leakage test every outage and each system hydrostatic test.

i

- - - - - - - , , - _ , . - , . ,, -,,-- - ,,--- -r- - . - - . . . - - . - - . ---n

If maintenance or operational problems are encountered which necessitate disassembly of the casing internals of either pump, a VT-1 examination of the interior casing surface will be performed. If a pump is not disassembled, this commitment will extend to the next inspection interval.

If a pump is disassembled to the extent that a radiographic examination is practical and a miniature linear accelerator (MINAC) is available, the code-required volumetric examination will be performed.

Once each interval, an exterior surface examination of approximately one-third of the accessible pump casing weld surface will be conducted in conjunction with a 100% exterior visual exatnination (VT-1). If the code-required examination is performed as discussed above, this examination is not necessary.

Reason for Relief Request The two reactor coolant pumps (RCP) for Point Beach Unit 2 are Westinghouse Model 93 pumps. Each pump casing is fabricated by welding four stainless steel (SA351 CF8) castings together.

Thus, there are three circumferential pressure-retaining welds that are to be volumetrically inspected in accordance with Category B-L-1. Because the physical properties of the stainless steel castings and weld material prevent meaningful ultrasonic examination, the casing welds must be inspected using the miniature linear accelerator (MINAC).

This radiographic examination is performed by placing the MINAC inside the pump casing and placing the film on the outside of the pump. To perform the examination, the pumps must be completely disassembled. Disassembly to this extent is far beyond any disassembly expected except for this examination.

Also, insulation on the casing exterior must be removed for film placement. Additionally, the pump bowl must be dry for installation of the MINAC. Therefore, all fuel assemblies must be removed from the reactor vessel and the vessel water level lowered to below the nozzles. Complete disassembly of the pump is also required to conduct the VT-1 examination in accordance

with Category B-L-2. i This radiographic examination using the MINAC was performed on Point Beach Unit 1 "B" RCP during the Fall 1981 refueling I outage. In addition, the same examination has been performed at j several other sites. No problems have been found with the welds i at any site. Additionally, no problems have been found during the Category B-L-2 visual examination. This visual examination was conducted at PBNP by using the video camera on the MINAC.

We believe that performing a volumetric examination of the Point

, Beach Unit 2 reactor coolant pump casing welds and a visual

) examination of the interior pressure retaining surface of one pump during the second ten year inspection period does not 2-

provide an increase in safety commensurate with the associated cost potential for inadvertent pump damage, and expected radiation exposure. The following items have been considered:

1. R.3diation Levels Currently the average does rates at the RCP are:

8' elevation general area < 1 - 25 mR/hr Below RCP ~ 10 - 800 mR/hr in RCP 700 - 10,000 mR/hr

2. Total Estimated Exposure During The Examination The whole body doses received during the fall 1981 examination of Unit 1, RCP-B are listed below. This list does not include the additional dose received while setting the plant to a condition where RCP disassembly could be performed (e.g., complete core unload).

- PBNP maintenance personnel during disassembly 5,237 mR

- Contractor personnel - diffuser adaptor removal 3,890 mR

- Contractor examination personnel 12,626 mR

- Contractor personnel - insulation 4,490 mR removal / replacement

- Contractor personnel - diffuser adapter 1,833 mR replacement

- PBNP Maintenance personnel - reassembly 6,017 mR TOTAL 34,093 mR

3. Pump Disassembly The Category B-L-1 and B-L-2 examinations require complete disassembly of the pump. The pump manufacturer (Westinghouse) does not require or recommend pump disassembly to perform normal maintenance or inspections.

The only time disassembly to this degree has ever occurred was to perform this examination during the fall of 1981.

Therefore, very limited experience in this area may result in significant damage or degradation to the pump.

Additionally, complete pump disassembly is not anticipated for any other reason in the foreseeable future.

1

4. Pump Performance i The type of materic1 used in these pumps is widely used thrcughout the industry and has performed very well. There have been no reported problems or failures with the casing welds of these model pumps. Additionally, the licensee has had no operational problems with the RCPs which could indicate potential degradation of the casing welds.

5. Excessive Cost The estimated cost to disassemble / reassemble the pump, remove and reinstall insulation and to perform the examination is approximately $810,000. Additionally, this examination is expected to extend the refueling outage a minimum of 5 days. Therefore, replacement power costs would be a minimum of about $1.5 million. Any minor problems which might occur could significantly increase the cost of the examination.

l

6. Alternative Examinations The alternative examinations we are proposing, as well as the already installed vibration monitoring system, will be sufficient to detect any problems which may occur.

l l (a) A visual (VT-2) exr.mination of the casing exterior will l be performed in conjunction with the system leakage test every outage and each system hydrostatic test.

(b) If maintenance or operational problems are encountered which necessitate disassembly of the casing internals of i either pump, a VT-1 examination of the interior casing surface will be performed. If a pump is not disassembled, this commitment will extend to the next l inspection interval.

i (c) If a pump is disassembled to the extent that a l radiograph examination is practical and a minature linear accelerator (MINAC) is available, the code-required volumetric examination will be performed.

(d) Once each intervar, an exterior surface examination of approximately one-third of the accessible pump casing l

weld surface will be conducted in conjunction with a 100% exterior visual examination (VT-1). If the l code-required examination is performed as discussed in 1

Item (c) above, this examination is not necessary.

(e) Vibration mon'. tors are currently installed on the motor frame near the lower radial bearing and on the motor shaft above the pump casing. These monitors will alarm i

l i

on panel C04 in the control room if either detects high I vibration. The PBNP Operating Procedures Manual provides reactor coolant pump vibration limits. If the )

i limits are exceeded, we would expect to shut down and  ;

determine the cause. These monitors would most likely l detect any problem which could lead to pump casing, l l welds, or rotating element failure.

?

l l

4 -

l

1 In conclusion, we believe that, based on the preceding items, performing the volumetric inspection of the RCP casing welds and the visual examination of the internal surface of the pump casing during the second ten-year interval do not provide a commensurate increace in safety. We, therefore, request approval of this relief request.

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