The Snubber Utility Group began at a December 6, 1984 snubber information exchange meeting in St. Petersburg, Florida. Twenty-six attendees representing eighteen utilities attended the meeting, hosted by Florida Power Corporation. The attendees decided that a Snubber Utility Group would be formed with the following goals:
- Proactively interact as a united utility group with the NRC, vendors, and ASME Code Committees on snubber matters.
- Share snubber information among the member utilities.
- Increase utility members’ efficiency in the procurement of snubbers and snubber related materials through the use of a snubber database.
Two specific items were identified as immediate concerns to be addressed by the group:
- Attachment2 – 1984 Outline for OM-4 Response to NRC concerns regarding large bore snubbers (Generic Issue 113).
- Revision of Technical Specification requirements for visual examinations and ASME OM-4 (1983 design outline).
The newly formed group elected officers and a Core Committee to provide leadership and continuity. At that time, it was also determined that the group would meet on a semiannual basis.
Since those early meetings, the basic format of SNUG conferences has not changed significantly. Emphasis is placed upon interaction among the technical specialists and engineers directly responsible for the “hands-on” administration of their plant’s snubber program. Vendor participation is encouraged, and one conference generally provides vendors a platform to display their products in a trade show format each year. Representatives from the NRC are also invited and are often in attendance to participate in discussions. Allowances are made for confidential utility-only sessions where members may speak freely about problems or concerns.
SNUG is governed by it’s “By Laws and Policy Statements”. Until recently the only requirement for membership was active participation and the providing of input to a snubber information database that was created for SNUG. Efforts to update the database from the 1985 version resulted in the development of a much more comprehensive and useful database, which was accessible through the Internet. However, costs associated with both the development and projected maintenance of the database and its associated Internet website required that a small annual membership fee be required from each member plant. Funds from this fee would also help supplement costs associated with the conferences, reducing the burden on the volunteering host utilities. The amount of the fee was set and approved by the membership, based upon the projected budget needs. Changes to the charter to allow for the collection of fees also resulted in the incorporation of SNUG as a not-for-profit organization. This incorporation allowed SNUG to maintain itself as an independent organization governed by the participating members. This has resulted in a “freedom of action” that many industry groups lack. Indeed, it is this independence that provides SNUG with credibility within the industry.
SNUG has a rich history of success in addressing industry snubber concerns. SNUG’s efforts have directly resulted in significant cost reduction opportunities for utilities, as well as fostering improvement in the reliability of the industry’s snubber populations. Some of the more significant accomplishments are listed below:
- SNUG officers and members made a number of successful presentations to the NRC in support of closing out the large bore snubber issue, Generic Issue 113. Data gathered and presented by SNUG was instrumental in preventing the imposition of unrealistically stringent testing requirements for large bore snubbers.
- Visual examination requirements were drastically reduced by Generic Letter 90-09, which directly referenced SNUG data as a basis for the relaxed requirements. Incorporation of GL 90-09 can reduce the required frequency of 100% visual examinations from once per cycle to as much as 48 months. Most plants that have incorporated the letter have reduced their visual examination costs by at least 50%, some by much more.
- SNUG provided a documented response to Information Notice 94-48, Snubber Lubrication Degradation in High Temperature Environments. The SNUG response offered clarification of some misconceptions with regard to the event that resulted in IN 94-48. The response also detailed SNUG Working Group efforts that were already responding to lubrication concerns even prior to the notice. Working in cooperation with the involved manufacturer, SNUG has addressed many of the concerns with the lubrication issue, and has been able to place this regulatory concern into a realistic perspective.
- SNUG has been able to utilize multi-utility working groups to provide a number of position, or “white” papers on snubber issues. Among these is a white paper clarifying the purposes and significance of spacer washers and the associated end gaps in snubber attachments. This paper has been successfully referenced by several utilities in response to regulatory concerns. A more recent paper on fretting corrosion has been utilized by snubber personnel to more accurately identify vibration-induced degradation that had previously been assumed to be associated with lubricant degradation. The proper identification of the failure mechanism significantly changes the scale (and cost) of the corrective actions taken, in that what was once thought to be a generic concern becomes a location specific issue.
- A Seal Life Resource Manual for hydraulic snubbers was compiled and distributed by SNUG. This manual has proven to be a valuable resource for snubber personnel in determining the proper seal materials to specify, as well as enabling them to develop cost effective maintenance programs.
- A presentation was made to the ASME ISTD Working Group providing the basis and plan to eliminate visual examinations (ASME ISTD has developed Code Case OMN-13 in response to the information provided by SNUG).
- SNUG facilitated an EPRI project on the evaluation of snubber test methods. This included the benchmarking of snubber test equipment.
- Implementation of the Improved Technical Specifications (ITS) relocated snubber requirements to 10CFR50.59 programs. The 72 hour window previously used to remove and test snubbers without affecting the supported system is no longer available. This results in forcing plants to either enter the system action statement immediately or to perform a qualifying analysis prior to removal. Either of these options place an undue burden on the owner. SNUG worked with the NRC and NSSS Owner’s Groups to develop a resolution to this issue.
- SNUG has developed a generic outline for a snubber program document. The document is intended to provide guidance for individual plants in developing site specific documents that detail their snubber programs. The intent is to encourage completeness and consistency among programs industry wide.
Current and Planned Activities
Mechanical Snubber Issues Working Group:
The working group is chartered to identify, prioritize, and address significant issues associated with mechanical snubbers. The working group is involved in updating a previously compiled Mechanical Snubber Issues Manual, which will serve as a single resource to address these issues. A major component of the manual is expected to be a failure analysis guide. The guide will provide detailed direction on the proper identification of failure mechanisms and causes based upon careful visual examination of snubber external and internal indications. It is hoped that this guide will result in a more consistent approach to failure analysis throughout the industry, making the data base information even more useful. The manual itself will be comprised of sections which will include such things as significant white papers, industry documents such as regulatory bulletins and letters, references to EPRI and INPO documents, utility and vendor contact lists and cross references, and utility case histories of significance. The manual will be a “living” document that will be continue to be updated periodically.
Hydraulic Snubber Issues Working Group:
This working group is very similar in purpose and scope to the Mechanical Issues Group. The working group is working to identify hydraulic snubber issues and resources. One of the tasks for the group is to review and update the seal life resource manual, which was previously compiled by SNUG. A comprehensive manual similar to the mechanical issues manual will result from this group’s work.
It should also be noted that updates are routinely provided from the two ASME subcommittees that have the most potential impact on snubber personnel. The ASME OM Subcommittee on Dynamic Restraints (ISTD) is responsible for writing and revising ASME Code in-service testing standards. The ASME Qualification of Mechanical Equipment (QME) Subcommittee on the Qualification of Dynamic Restraints (QDR) is responsible for maintaining the standard for the initial design qualification of dynamic restraints, including snubbers. SNUG members currently chair each of these subcommittees and several SNUG officers and members participate as subcommittee members. This high level of participation enables SNUG to maintain an effective voice in the code process and provides opportunities for the SNUG membership to provide significant input.
Obviously a complete history of SNUG and an enumeration of all the current and planned activities is far too detailed for this site. It is hoped, however, that it is also obvious that SNUG is a vibrant, ambitious organization comprised of dedicated and knowledgeable individuals. In this age of workforce reductions the number of true subject matter experts in any field is rapidly dwindling, and the area of snubbers is no exception. SNUG is dedicated to maintaining an effective knowledge base of industry experience, but utility participation is vital to our success. For over thirty five years SNUG has worked to compile and disseminate information on snubber examinations, testing, and evaluation. SNUG has been and will continue to be active participants in the development of new snubbers, snubber replacement devices, snubber reduction strategies, and snubber test equipment. SNUG has developed working relationships with both manufacturers and regulators, and serves as an effective liaison to both.