Resolution of Generic Safety Issues: Issue 176: Loss of Fill-Oil in Rosemount Transmitters (Rev. 1) ( NUREG-0933, Main Report with Supplements 1–34 )
The Rosemount Transmitter Review Group (RTRG) was established1659 to perform an assessment of the actions taken to address Rosemount transmitter oil-loss concerns. This assessment included an evaluation of the adequacy of the information and actions specified in NRC Bulletin 90-01,1658 Supplement 1, which informed licensees of activities undertaken by the NRC and the industry in evaluating and addressing loss of fill-oil in Rosemount transmitters manufactured prior to July 11, 1989, and requested licensees to take actions to resolve the concerns.
An action plan was developed by the staff and integrated the following RTRG recommendations to address Rosemount transmitter loss of fill-oil concerns: (1) conduct temporary instruction (TI) inspections to verify commitments made by licensees to address the requested actions of NRC Bulletin 90-01,1658 Supplement 1, and to gather plant-specific data on Rosemount transmitter failures; (2) establish a dialogue with Rosemount, Inc., on Rosemount transmitter failure information; (3) review NPRDS data on Rosemount transmitter performance; and (4) review EPRI Report TR-102908, "Review of Technical Issues Related to the Failure of Rosemount Pressure Transmitters Due to Fill-Oil Loss," dated August 1994. This issue was identified in an NRR memorandum1601 to RES in February 1996.
Loss of fill-oil in Rosemount transmitters was determined to be a potentially undetected means of common mode failure. Such failures could result in loss of automatic reactor protection and engineered safety feature actuations.
The staff determined that actions were needed by licensees to ensure that safety-related functions were maintained. These actions were first identified in Bulletin 90-011658 and subsequently modified in Bulletin 90-01,1658 Supplement 1. The time frame for this action plan was based on the fact that licensees had implemented the requested actions of Bulletin 90-01,1658 Supplement 1, and the plan was intended only as confirmation of the adequacy of the actions called for in the Bulletin.1658
The activities specified in the action plan were completed as a follow-up and verification of the implementation of the requested actions in Bulletin 90-01,1658 Supplement 1. Licensees addressed the common mode failure concerns by either replacing affected transmitters with newly designed transmitters which corrected the oil leakage problem, or subjecting affected transmitters to enhanced surveillance monitoring to ensure their proper performance. A two-year period was established for completing the necessary verification activities recommended by the RTRG including TI inspections and reviews of recent Rosemount transmitter performance.
Temporary Instruction (TI) 2515/122, "Evaluation of Rosemount Pressure Transmitter Performance and Licensee Enhanced Surveillance Programs," was issued on March 17, 1994 and inspections were initiated in May 1994. Based on the results of the TI effort, the staff determined that licensees were effectively addressing the Rosemount transmitter loss of fill-oil issue by, in general, following the requested actions of Bulletin 90-01,1658 Supplement 1, and the manufacturer's drift trending guidance.
The staff met periodically (between January 1994 and September 1995) with Rosemount, Inc. to exchange information on Rosemount transmitter performance. In addition, the staff completed NPRDS reviews for Rosemount transmitter failure information during the same period. Based on the information presented by Rosemount, Inc. and the results of the NPRDS reviews, the staff concluded that there was a significant decrease in the number of fill-oil failures since the issuance of Bulletin 90-01,1658 Supplement 1.
On February 15, 1995, the staff completed its review of EPRI Report TR-102908 and confirmed that it was substantially in agreement with the previous conclusions, guidance, and requested actions contained in Bulletin 90-01,1658 Supplement 1.
Based on the results of the above activities completed, the staff confirmed that all pertinent information regarding loss of fill-oil in Rosemount transmitters was contained in Bulletin 90-01,1658 Supplement 1, and Rosemount technical guidance. Therefore, the staff concluded that the safety concern of the issue had been effectively resolved by the actions taken and no changes or additional actions were warranted. Thus, this issue was RESOLVED and no new requirements were issued.1731