Issue 176: Loss of Fill-Oil in Rosemount Transmitters

DESCRIPTION

Historical Background

The Rosemount Transmitter Review Group (RTRG) was established[1] 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,[2] 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,[3] 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 memorandum[4] to RES in February 1996.

Safety Significance

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.

Possible Solution

The staff determined that actions were needed by licensees to ensure that safety-related functions were maintained. These actions were first identified in Bulletin 90-01[5] and subsequently modified in Bulletin 90-01,[6] 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,[7] Supplement 1, and the plan was intended only as confirmation of the adequacy of the actions called for in the Bulletin.[8]

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,[9] 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.

CONCLUSION

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

s

Rosemount transmitter loss of fill-oil issue by, in general, following the requested actions of Bulletin 90-01,[10] 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,[11] 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,[12] 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,[13] 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.[14]