Bulletin 78-10: Bergen-Paterson Hydraulic Shock Suppressor Accumulator Spring Coils
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, D. C. 20555
June 27, 1978
IE Bulletin No. 78-10
BERGEN-PATERSON HYDRAULIC SHOCK SUPPRESSOR ACCUMULATOR SPRING COILS
Description of Circumstances:
During the conduct of hydraulic shock suppressor (snubber) functional
testing and seal replacement programs at several licensed facilities, a
number of broken accumulator spring coils have been found in early model
Bergen-Paterson hydraulic snubbers. The attached extract from a Bergen-
Paterson advisory letter, dated April 6, 1978, states that a broken
accumulator spring alone would not render the snubber incapable of
performing its design function; however, the broken spring could cause
internal damage to the accumulator which could result in unit inoperability.
The subject snubbers are of the external pipe design with serial numbers
487,000 to 515,000 and F60,635 through F75,000. The accumulator springs in
these snubbers are basically carbon steel and were coated with a
petro-chemical rust preventative by the vendor. Despite this initial
protective coating, those springs found broken exhibited advanced stages of
corrosion. The factors which caused the spring corrosion are undetermined.
Bergen-Paterson has recommended that corrosion susceptible accumulator
spring coils be replaced with teflon coated or stainless steel coils during
the next refueling shutdown.
Action to be Taken by Licensees:
For all power reactor facilities with an operating license or a construction
1. If you have received the enclosed Bergen-Paterson letter addressing the
accumulator spring problem, and if you have those units installed or in
ready spares at your facility, it is requested that you describe what
corrective action you have taken or plan to take to assure that the
operability of snubbers in safety related systems is not impaired. It
is also requested that you describe the condition of any springs that
were observed during the performance of the corrective action.
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IE Bulletin No. 78-10 June 27, 1978
2. If you have not received the enclosed Bergen-Paterson letter, it is
requested that you describe what action you plan to take if the subject
snubbers are installed or in ready spares at your facility to assure
that the operability of snubbers in safety related systems is not
3. If the snubbers are currently installed in safety related systems, it
is requested that you identify their location in your response to this
4. Report in writing within 45 days for facilities with an operating
license and within 60 days for facilities with a construction permit,
your plan of action and schedule with regard to Items 1, 2 and 3.
Reports should be submitted to the Director of the appropriate NRC
Regional Office and a copy should be forwarded to the NRC Office of
Inspection and Enforcement, Division of Reactor Operations Inspection,
Washington D. C. 20555.
Approved by GAO, B180225 (R0072); clearance expires 7-31-80. Approval was
given under a blanket clearance specifically for identified generic
Extract from Bergen-Paterson
letter dated April 6, 1978
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Extract from Bergen-Paterson Advisory Letter
SUBJECT:B/P Hydraulic Snubbers
HSSA Accumulator Spring
Bergen-Paterson advises that broken accumulator spring coils have been found
in a number of early model hydraulic snubbers at the time when units were
being dissembled for seal replacement purposes. The early models noted are
identified as being the external pipe design having serial numbers between
487,000 and 515,000 and F60,635 through F75,000. These units were initially
furnished with music wire or chrome silicone spring material both coated
with a rust preventative. All later external pipe design units were
initially furnished with springs having the same material as noted above;
however, all coils were teflon coated. Our current model units are furnished
with stainless steel coils. Both the teflon coated and stainless coils have
been found to give satisfactory service.
It is specifically pointed out that a unit remains functional even with a
broken spring; however, the possibility does exist that the debris from a
broken spring coil could in fact cause damage to the Accumulator Piston
U-Cup Seal resulting in possible leakage of fluid. The remote possibility
for the Accumulator Piston to become jammed in the tube also exists
although, however, this has not been experienced.
Bergen-Paterson has issued this advisement to make users aware of the
possibility of broken accumulator springs and recommends that units having
uncoated coils be refitted with either teflon coated or stainless steel
coils at the next refueling shutdown.
Very truly yours,
BERGEN-PATERSON PIPE SUPPORT CORP.
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