IR 05000306/1978023
| ML19282B089 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 01/19/1979 |
| From: | Danielson D, Yin I NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | |
| Shared Package | |
| ML19282B088 | List: |
| References | |
| 50-306-78-24, NUDOCS 7903090004 | |
| Download: ML19282B089 (10) | |
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U.S. NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT
REGION III
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Report No. 50-306/78-24 Docket No. 50-306 License No. DPR-60 Licensee:
Northern States Power Company 404 Nicollet Mall Minneapolis, MN 55401 Facility Name:
Prairie Island Nuclear Generating Plant, Unit 2 Inspection At:
Prairie Island Site, Red Wing, MN Inspection Conducted:
November 29-30, December 1 and 20, 1978 l ' *, *:,y
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Inspector:
I. T. Yin k/Nc'nsa2 lz.~
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Approved By:
.D.
H. Danielson, Chief
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Engineering Support Section 2
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Inspection Summary Inspection Condacted on November 29-30, December 1 and 20, 1978 (Report No. 50-306/78-16)
Areas Inspected:
Surveillance of safety related pipe supports and restraints including:
(1) review of program and procedures, (2)
snubber qualification data, (3) installed hardware conditions, and (4) review of maintenance records. The inspection involved a total of 21 inspector-hours onsite by one NRC inspector.
Resultr:
No items of noncompliance or deviations were identified.
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i DETAILS Persons Contacted fr
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Principal Licensee Employees
- G.
H. Neils, General Superintendent
- F.
P. Tierney, Plant Manager
- E.
Watzl, Plant Superintendent, Engineering and Radiation Protection
- D. Mendele, Plant Superintendent, Operation Engineering
- A. D. Smith, Product Engineer
- S.
Guokas, Plant Engineer Nutech D. K. McWilliams, Project Engineer T. N. Vogel, Project Engineer
- Denotes some of those present at the exit interview on December 1, 1978.
Functional or Program Areas Inspected 1.
General The various types and sizes of safety related pipe and equip-ment hydraulic snubbers installed at Prairie Island Units 1 and 2 at present, prior to planned FSAR changes, contain:
a.
Basic Engineers (BE) Snuboers Quantity Bore and Stroke
3/4 x 5
1x5
1 1/2 x 5
1 1/2 x 10
2x5
2 1/2 x 5
3 1/4 x 5
4x5
5x5
8x5
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b.
Anker Holth (AH) Snubbers Quantity Capacity and Stroke
90 kips x 4
6 kips x 3.5
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BE snubber sizes 1 1/2 x 5, 2 x 5, and 2 1/2 x 5 have been tested dynamically. The other BE snubbers had never been test proven to be qualified under seismic and adverse environmental conditions.
At the time of the inspection and design, test data were not available for AH snubbers.
The inspector's comments on the various tests performed by BE and the lack of comprehensive snubber func-tional qualification testings are discussed in the report.
2.
Review of Procedures The safety related snubber surveillance requirements are documented in Technical Specifications (TS) Section 3.12 relative to the limiting conditions for operation and Section 4.13 relative to surveillance requirements.
The licensee stated that the TS is being revised and a future FSAR amendment will include hydraulic snubber improved functional testing requirements and add approximately 112 snubbers to the TS for Units 1 and 2.
Procedure, Test No.
2171, " Tech Spec Shock Suppressor Check," Revision 1, which implements the present TS requirements, was reviewed by the inspector. The inspector considered the procedure sufficient except in the following two areas:
a.
There appeared to be no requirement for recording leakage locations so that meaningful evaluation can be done to access the significance and required fix-ups.
b.
There were no provisions for measuring the cold position setting (CPS) and hot position setting (HPS) to ensure the settings are in accordance with the design.
The licensee is in the process of upgrading procedural requirements and item b. above concerns had been performed on an informal basis.
During followup discussion on December 20, 1978, the licensee stated that HPS had been verified by the A-E after hot functional testing and the data is retrievable.
This is an unresolved item pending future inspection followup and record review.
(306/78-16-01)
No items of noncompliance or deviatisns were identified during the above review.
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Snubber Functional and Qualification Requirements The inspector reviewed the Fluor Pioneer Incorporated (FPI), the Architect-Engineer, Specification SS-M426 4-63 " Standard Specifi-cation for Pipe Support Design, Fabrication and Erection", Revision 1-69, and found functional and qualification test requirements had not been specified. The following areas require clarification: (1)
Without functional requirements, how did the manufacturer know what to supply, and (2) without qualification test requirements, how did the licensee assure that the snubbers can perform their intended function at seismic and adverse environmental conditions. This is an unresolved item.
(306/78-16-02)
No items of noncompliance or deviations were identified during the above review.
4.
BE Production Quality Control Documents reviewed verified that the safety related snubbers purchased in 1969 were classified as QA type III, non-safety related items.
The snubbers were reclassified as safety related in 1974. Further, in Teledyne Material Research Technical Report E-1963, " Performance Test of Hydraulic Snubbers" dated December 19, 1974, Paragraph 6 states that, "Due to the extremity low locking velocity, BE personnel requested that the orifice in the poppet valves of Units 5 and 6 be enlarged.
The valves were removed from the snubbers and disassembled.
Each valve assembly was found to contain two different styles of poppets, one with smooth sides and one with ribbed sides. On closer inspection the poppet removed from the tension side of Unit 6 was found to have a large burr in the orifice.
This significantly reduced the area of the orifice and thereby the locking velocity.
The fact explains why the locking velocity in tension is slower than the compression locking velocity for Unit 6.
Since the poppet la the Units 5 and 6 were of the wrong type, Mr. Eliot Martin decided to exchange the valves with the valves of two other snubbers.
When this was done it was discovered that two more of the test snubbers had two styles of poppets.
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." Considering there were only six snubbers being testing, the inspector considers the number of deficiencies identified to be significant. The adequacy of the BE production quality control and the adequacy of licensee vendor surveillance and audit as well as receipt inspection are questionable.
This is an unresolved item.
(306/78-16-03)
No items of noncompliance or deviations were identified during the above review.
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Snubber Dynamic Testing At present, the Unit 1 TS lists 52 snubbers that were manuf actured by BE with load capacities ranging from 738 pounds to 113 kips, and 3 that were manuf actured by AH (2 of these are 6 kip units and one 90 kip unit); the Unit 2 TS lists 50 snubbers that were manufactured by BE with capacity a range the same as in Unit 1, and AH snubbers the same as Unit 1.
During a phone conversation with the BE repre-sentative, it was stated that only 3 small sizes of snubbers with capacity up to 11 kips had been tested dynamically, that some problems were identified during testing, and that the data had not been evaluated by the AE.
Subsequently, a meeting was held on December 20, 1978, and the Nutech Report, No. NSP-32-003, " Basic Engineering Snubber Evaluation, Prairie Island Nuclear Generating Plant," Revision 0, dated December 15, 1978, was presented to the inspector.
The applicable BE cnubber dynamic test data contained in Report NSP-32-003 was examined by the inspector.
The test specimans included poppet valves with 0.070' diameter orifice (representing Prairie Island snubbers). The test setting was believed to be at mid-stroke and the fluid was GE SF-1154.
The test was run at 3, 6, 9, and 12 cycles per second with applied constant displacement that varies approximately as the sine wave. The applicable data is shown in the following table:
Dynamic Dynamic Rated Load Responses Responses in Total Loss Total Dynamic Snubber Capacity in Tension Compresson of Motion Displacement Bore and Stroke (kips)
(kips)
(kips)
(in.)
(in.)
1 1/2 x 5 3.7
3.4 to 0.05 0.06 4.2 (approx.)
(approx.)
2x5 7.0 1.5 to
0.04 0.102 2.2 (approx.)
(approx.)
2x5 7.0 5 to 7
0.04 0.125 to 0.15 2 1/2 x 5 11.0
11 0.04 to 0.075 to 0.05 0.08 2 1/2 x 5 11.0 2.5
0.03 0.075 to (approx.)
0.10
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LOCKING VELOCITIES OF PRAIRIE ISLAND SNUPBERS Snubber Locking Velocity (Inches / Minute)
ITT Grinnell
Anker-Holth Type I
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Anker-Holth Type II
.2 Anker-Holth Type III
.05 Basic Engineers - 3/4 inch
Basic Engineers - 1 inch
Basic Engineers - 1 1/2 inch
Basic Engineers - 2 inch
Basic Engineers - 2 1/2 inch
Basic Engineers - 3 1/4 inch
Basic Engineers - 4 inch
Basic Engineers - 5 inch
<1 Basic Engineers - 6 inch
<1 Basic Engineers - 8 inch
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Basic Engineers - 10 inch
<1 The following items require clarification:
The low LV's shown for AH snubbers Types I, II, and III a.
could prevent proper thermal movements of the pipe system.
b.
The high LV's for the BE snubber 3/4 inch size could al'ter the dynamic functional characteristics that are required to control system vibratory motions.
The uncertain LV's shown for the BE 5 inch to 10 inch snubbers c.
could cause undesirable system stress or affect the protective functions of the snubber.
During the December 20, 1978, meeting, the Nutech engineer stated that the piping thermal growth rate was calculated to be 0.1-0.75 inch / minute and a table of average LV's for all sizes BE was presented to the inspector.
The inspector stated that the following areas required clarification:
(1) now that we know the AH LV may interfere with pipe thermal movement, what, if any, corrective sition war caken, (2)-why was there no dynamic test in conjunction with the LV to ensure the higher LV would not affect-7-
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The inspector stated clarification is required relative to: (1)
zero dynamic tension responses at mid-stroke settings for some of the BE snubbets, (2) whether or not some of the larger dynamic displacement shown in BE data could cause change of system natural frequencies calculated by the AF, (3) whether or not the three smaller size (up to 11 kips) BE snubbers could meaning, fully reprecent all the other larger or smaller units from 0.74 to 113.0 kips, and (4) the lack of design and test data for AH snubbers. This is an unresolved item.
(306/78-16-04).
No ite ms of noncompliance or deviations were identified during the above review.
6.
Effects Due to Creep Rate Adjustment The inspector reviewed the creep rate for the snubbers and determined:
a.
No creep (or bleed) rate data was available for AH snubbers.
b.
The present BE snubber creep rate is adjusted to a 1/8 turn setting.
The creep rate data at this setting was not available for review.
It was stated in Paragraph 3 of the 1974 Tele' dyne Report E-1963 c.
that "The amount of movement with the needle valves closed is essentially zero.
The amount the needle valves are opened is very critical for if the needle valves were open 1/8 turn, then the creep rate became so large that the unit could not develop full rated load."
In regard to the 1/8 turn creep rate setting for the BE snubbers, the inspector stated clarification is required relative to:
(1)
since the dynamic testing was done with the creep needle closed, why did the manufacturer recommended 1/8 turn setting for the plant, and (2) what percentage of capacity is lost at the 1/8 turn setting (will it still meet the design loading requirement?). This is an unresolved item.
(306/78-16-05)
No items of noncompliance or deviations were identified during the above review.
7.
Snubber Lock-up Velocities During review of a FPI letter, No. F-N-0096, to the licensee dated May 20, 1975, subject:
" Draft Response to Item I.a. IE Bulletin No. 75-05", the inspector noted that a table attached to the letter listed the locking velocities (LV's) of the BE and AH snubbers as follows:
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the dynamic performance characteristics, and (3) why was there no environmental test in conjunction with the LV to ensure higher temperature and humidity would not increase the LV excessively.
This is an unresolved item.
(306/78-16-06)
No items of noncompliance or deviations were identifie'd in the above area.
8.
Snubber Environmental Testing In this area the ins-7ctor determined that; a.
Design and test data were not available for AH snubbers, b.
Test data for BE snubber components, including seal materials and hydraulic fluid, were available and the inspector had no adverse comments.
c.
The change of functional characteristic of BE hydraulic snubbers at elevated design temperature and in high humidity conditions was not evaluated based on testing or other suitable means.
Items a and c are considered unresolved items.
(306/78-16-07)
No items of noncompliance or deviations were identified in this area.
9.
Special BE Snubber Design Considerations As a result of his review of the design of the BE snubbers, the inspector stated the following areas require clarification:
a.
There are small needle valves and orifice openings within the control valve unit, and there is no built-in filtering mechanism to prevent plugging up of these small holes. During the December 20, 1978, meeting the license stated that they have a snubber fluid filtering and foreign particle test program in existance.
The inspector stated that he would inspect the program during a future visit.
This is an unresolved item.
(306/78-16-08)
b.
The fluid reservior is positioned in line with the cylinder.
For horizontal installation, the level of the fluid in the reservoir is always below that in the cylinder.
If there is any seal leakage anywhere on the cylinder wall, the vacuum may be able to draw air into the cylinder and thus drastically reduce the effectiveness of the snubber.
During the December 20, 1978, meeting the licensee stated that their present snubber surveillance program requires-8-
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all Icaking snubbers be removed for seal replacement, exam-ination and testing.
In addition, the licensee stated that a Bergen-Paterson test rig will be delivered at the si ' in January, 1979, for snubber LV and crepp rate testing.
The inspector stated that he would review the testing procedures and observe the program implementation during a future inspection.
This is an unresolved item.
(306/78-16-09)
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No items of noncompliance or deviations were identified in the above area.
10.
Observation of Snubber and Hanger Conditions The inspector observed approximately 20 safety related BE and AH pipe snuobers in the containment and auxiliary building areas. The conditions appeared to be good except one 1 1/2" x 5" stroke BE snubber, 2RHRRH-9 showed small leakage.
The licensee indicated that they had not inspected these snubbers, and that they will document and fix any problems identified prior to plant startup.
The inspector observed the four large McDowell Wellman snubbers installed on Loop B steam generator, and approximately 10 spring hangers in the areas.
No significant rejectable conditions were observed by the inspector.
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The licensee is in the process of replacing seal material in all 387 safety and non-safety snubbers in Units 1 and 2 with the E-P seals.
All seals in the 43 safety related snubbers in both Units 1 and 2 containments were replaced in 1976.
Seal replacements were performed on 252 additional safety and non-safety snubbers during 1978.
The nine large size BE snubbers (sizes 4 x 5, 5 x 5, and 8 x 5) were shipped to the manufacturer for seal replacement, LV, and bleed rate tests.
The smaller BE snubbers and the AH snubbers were serviced and tested at the site.
The inspector observed the areas for the seal replacement and testing and had no adverse comments.
No items of noncompliance or deviations were identified in the above area.
Unresolved Items Unresolved items are matters about which more informatien is required in order to ascertain whether they are acceptable items, items of noncom-pliance, or deviations. Unresolved items disclosed during this inspection are discussed in Paragraphs 2, 3, 4, 5, 6, 7, 8, 9.a. and 9.b of this report.
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Exit Interview The inspector met with site representatives (denoted in the Persons Contacted paragraph) at the conclusion of the inspection on December 1, 1978.
The inspectc,e summarized the scope and findings of the inspection noted in this report.
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