United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 83-47: Failure of Hydraulic Snubbers as a Result of Contaminated Hydraulic Fluid

                                                            SSINS No.: 6835 
                                                            IN 83-47       

                                UNITED STATES
                        NUCLEAR REGULATORY COMMISSION
                    OFFICE OF INSPECTION AND ENFORCEMENT
                           WASHINGTON, D.C., 20555
                                     
                                July 12, 1983

Information Notice No. 83-47:   FAILURE OF HYDRAULIC SNUBBERS AS A RESULT
                                   OF CONTAMINATED HYDRAULIC FLUID 

Addressees: 

All nuclear power reactor facilities holding an operating license (OL) or 
construction permit (CP). 

Purpose: 

This information notice is provided as a notification of a recently observed
failure of hydraulic snubbers because hydraulic fluid was contaminated. No 
specific action is required in response to this information notice, but it 
is expected that recipients will review the information presented for 
applicability to their facilities. 

Description of Circumstances: 

On May 31, 1983, the Florida Power Corporation reported (LER 83-021) the 
failure of 107 out of 261 hydraulic snubbers to meet their functional test 
requirements at Crystal River Unit 3. Contaminated hydraulic fluid was the 
most frequently cited cause. 

During Crystal River's 1981 refueling outage, a similarly high failure rate 
was observed and reported (LER 81-063 and its revision). An evaluation of 
the event indicated that the most likely source of contamination was 
particulate matter left in the fluid reservoirs after fabrication. 
Consequently, the corrective action was limited to disassembling, cleaning, 
reassembling, and filling all the snubbers with new fluid. 

Following this latest failure, other sources of contamination were 
investigated with the result that the possible sources now are considered to
be the fluid reservoir, the reservoir vent opening, and the new hydraulic 
fluid (GE type SF9650). In addition, the corrective actions have been 
expanded and now include the following. 

1.   The reservoir manufacturer has been required to flush each reservoir 
     with clean solution before shipping it to the facility. 

2.   Independent pre-shipment inspections are performed to verify 
     cleanliness before sending new reservoirs to the facility. 



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                                                              IN 83-47     
                                                              July 12, 1983 
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3.   Reservoirs are flushed with cleaning solution before the snubber is 
     assembled. 

4.   Reservoir vents that are open to the atmosphere have been replaced with
     filtered vents.  

5.   New hydraulic fluid is being filtered several times before use. First, 
     the fluid is filtered as it is poured from the shipping container. The 
     fluid is filtered again as it is pumped into the snubber. And, finally,
     following filling, the snubber is stroked several times and the 
     displaced fluid passes through a filter and returns to the snubber with
     each stroke. 

No written response to this notice is required. If you have any questions 
regarding this matter, please contact the Regional Administrator of the 
appropriate NRC Regional Office, or this office. 


                                   Edward L. Jordan Director 
                                   Division of Emergency Preparedness 
                                     and Engineering Response 
                                   Office of Inspection and Enforcement 

Technical Contact:  R. J. Kiessel, IE
                    (301) 492-8119

Attachments:
List of Recently Issued IE Information Notices

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