United States Nuclear Regulatory Commission - Protecting People and the Environment

Alternative Requirements for Snubber Visual Inspection Intervals and Corrective Actions (Generic Letter 90-09)



December 11, 1990


T0:       ALL LIGHT-WATER REACTOR LICENSEES AND APPLICANTS

SUBJECT:  ALTERNATIVE REQUIREMENTS FOR SNUBBER VISUAL INSPECTION INTERVALS 
          AND CORRECTIVE ACTIONS (GENERIC LETTER 90-09)


Technical Specifications (TS) impose surveillance requirements for visual 
inspection and functional testing of all safety-related snubbers.  A visual 
inspection is the observation of the condition of installed snubbers to 
identify those that are damaged, degraded, or inoperable as caused by 
physical means, 1eakage, corrosion, or environmental exposure.  To verify 
that a snubber can operate within specific performance limits, the licensees 
perform functional testing that typically involves removing the snubber and 
testing it on a specially-designed test stand.  Functional testing provides 
a 95 percent confidence level that 90 percent to 100 percent of the snubbers 
operate within the specified acceptance limits.  The performance of visual 
examinations is a separate process that complements the functional testing 
program and provides additional confidence in snubber operability.

The TS specifies a schedule for snubber visual inspections that is based on 
the number of inoperable snubbers found during the previous visual 
inspection. The schedules for visual inspections and for the functional 
testing assume that refueling intervals will not exceed 18 months.  Because 
the current schedule for snubber visual inspections is based only on the 
number of inoperable snubbers found during the previous visual inspection, 
irrespective of the size of the snubber population, licensees having a large 
number of snubbers find that the visual inspection schedule is excessively 
restrictive.  Some licensees have spent a significant amount of resources 
and have subjected plant personnel to unnecessary radiological exposure to 
comply with the visual examination requirements.

To alleviate this situation, the staff has developed an alternate schedule 
for visual inspections that maintains the same confidence level as the 
existing schedule and generally will allow the licensee to perform visual 
inspections and corrective actions during plant outages.  Because this 
line-item TS improvement will reduce future occupational radiation exposure 
and is highly cost effective, the alternative inspection schedule is 
consistent with the Commission's policy statement on TS Improvements.

The alternative inspection schedule is based on the number of unacceptable 
snubbers found during the previous inspection in proportion to the sizes of 
the various snubber populations or categories.  A snubber is considered 
unacceptable if it fails the acceptance criteria of the visual inspection.  
The alternative inspection interval is based on a fuel cycle of up to 24 
months and may 


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be as long as two fuel cycles, or 48 months for plants with other fuel 
cycles, depending on the number of unacceptable snubbers found during the 
previous visual inspection.

Guidance on implementing the alternative TS requirements for visual 
inspection intervals is provided in Enclosures A and B.  Licensees and 
applicants are encouraged to propose changes to their TS that are consistent 
with this guidance.  The NRC project manager will expeditiously review 
conforming amendment requests for the facility.  Questions on this matter 
should be addressed to the contact listed below or to the project manager.

This request is covered by Office of Management and Budget Clearance Number 
3150-0011, which expires January 31, 1991.  The estimated average number of 
burden hours is 40 person hours per licensee response, including searching 
data sources, gathering and analyzing the information, and writing the 
requested reports.  Send comments regarding this burden estimate or any 
other aspect of this collection of information, including suggestions for 
reducing this burden, to the Information and Records Management Branch, 
Division of Information Support Services, Office of Information and 
Resources Management, U.S. Nuclear Regulatory Commission, Washington, D.C. 
20555; and to the Paperwork Reduction Project (3150-0011), Office of 
Management and Budget, Washington, DC 20503.

                              Sincerely,


                              James G. Partlow
                              Associate Director for Projects 
                              Office of Nuclear Reactor Regulation

Enclosure:
As stated

Contact:  Jai Rajan (301) 492-0788
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                                                                 Enclosure A


               ALTERNATIVE REQUIREMENTS FOR DETERMINING THE INTERVAL
                    FOR THE VISUAL INSPECTION OF SNUBBERS


An alternate method for determining the next interval for the visual 
inspection of snubbers is provided based upon the number of unacceptable 
snubbers found during the previous inspection, the total population or 
category size for each snubber type, and the previous inspection interval.  
A snubber is considered unacceptable if it fails to satisfy the acceptance 
criteria of the visual inspection.  Snubbers may be categorized, based upon 
their accessibility during power operation, as accessible or inaccessible.  
These categories may be examined separately or jointly.  However, the 
licensee must make and document that decision before any inspection and 
shall use that decision as the basis upon which to determine the next 
inspection interval for that category.

If a licensee's review and evaluation can not justify continued operation 
with an unacceptable snubber, the licensee shall declare the snubber 
inoperable and shall meet the applicable action requirements.  To determine 
the next surveillance interval, the licensee may reclassify an unacceptable 
snubber as acceptable if it can be demonstrated that the snubber is operable 
in its as-found condition by the performance of a functional test and if it 
satisfies the acceptance criteria for functional testing.

The next visual inspection interval may be twice, the same, or reduced by as 
much as two-thirds of the previous inspection interval.  This interval 
depends on the number of unacceptable snubbers found in proportion to the 
size of the population or category for each type of snubber included in the 
previous inspection.  Table 4.7-2 in Enclosure B replaces the existing TS 
requirements for determining the next visual inspection interval.  
Generally, the existing TS requirements establish inspection intervals of 18 
months (the length of a nominal fuel cycle) or a fraction thereof based on 
the number of inoperable snubbers of each type for the previous inspection 
period.

The alternative provided herein allows inspection intervals to be compatible 
with a 24-month fuel cycle.  Also, the interval may be increased to every 
other refueling outage for plants on a 24-month fuel cycle or up to 48 
months for plants with other fuel cycles if few unacceptable snubbers were 
found from the previous inspection.  Table 4.7-2 establishes three limits 
for determining the next visual inspection interval corresponding to the 
population or category size for a given type of snubber.  The three limits 
are listed in Columns A, B, and C of Table 4.7-2 for representative sizes of 
snubber populations or categories.  For a population or category that 
differs from the representative size provided, the values for the limits may 
be found by interpolation from the limits provided in Columns A, B, and C 
for determining the next inspection interval.  Where the limit for 
unacceptable snubbers in Columns A, B, or C is determined by interpolation 
and includes a fractional value, the limit may be reduced to the next lower 
integer.

The limits in columns A, B, and C of Table 4.7-2 are applied as follows to 
determine the next inspection interval.  If the number of unacceptable 
snubbers is less than or equal to the number in Column A, the next 
inspection interval may be twice the previous interval but not greater than 
48 months, excluding the TS provisions to extend surveillance intervals.  If 
the number of unaccept-able snubbers is greater than the number in Column A 
but less than or equal to

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the number in Column B, the next inspection interval shall be the same as 
the previous interval.  If the number of unacceptable snubbers is equal to 
or greater than the number in Column C, the next inspection interval shall 
be reduced to two-thirds of the previous interval.  However, if the number 
of unacceptable snubbers is less than the number in Column C and greater 
than the number in Column B, the next inspection interval shall be reduced 
proportionally by a factor that is one-third of the ratio of the difference 
between the number of unacceptable snubbers and the number in Column B to 
the difference between the numbers of Columns B and C.

Enclosure B is a sample of the changes that should be proposed for TS that 
are based upon the format of the current Standard Technical Specifications 
(STS). For plants that have TS in a format different from the STS, proposed 
TS changes should be consistent with the changes provided in Enclosure B.  
The changes for this alternative are underlined, and Table 4.7-2 has been 
added.

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