United States Nuclear Regulatory Commission - Protecting People and the Environment

ACCESSION #: 9812140022


2/10/1998

U.S. Nuclear Regulatory Commission Operations Center Event Report

Page 1

Other Nuclear Material Event# 35129
Rep Org: FISHER-ROSEMOUNT Notification Date / Time: 12/09/1998
12:17 (EST)
Licensee: FISHER-ROSEMOUNT Event Date / Time: 12/09/1998
11:17 (CST)
Last Modification: 12/09/1998
Region: 3 Docket #:
City: Eden Prairie Agreement State: No
County: License #
State: MN
NRC Notified by: JERRY HANSON Notifications: MARK RING R3
HQ Ops Officer: JOHN MacKINNON VERN HODGE NRR
Emergency Class: NON EMERGENCY JOHN ROGGE R1
10 CFR Section: DAVID GRAVES R4
21.21 UNSPECIFIED PARAGRAPH CHARLES OGLE R2

10 CFR PART 21 REPORT REGARDING ROSEMOUNT MODEL 710 TRIP UNITS

Rosemount Nuclear Instrumentation, Inc. (RNII) has determined that they have a potential deviation related to certain 710DU0TS 4-20 mA master trip units. A jumper wire (J1) may be incorrectly installed on the circuit card assembly (CCA) of the master trip units. This jumper should only be installed on the CCA's of Mode 710DU0TS slave trip units. This jumper bypasses a buffer circuit that serves to protect the 1-5 volt bus of the master trip unit from electrical faults on a slave unit(s). This circuit configuration places the master trip unit in an unqualified (untested) condition and may expose the master trip unit to an unanalyzed failure mode.

FISHER-ROSEMOUNT

Rosemount Nuclear Instruments, Inc.
12001 Technology Drive
Eden Prairie, MN 55344-3695
USA


DATE: December 9, 1998 PAGE(S) INCLUDING LEAD SHEET: 8
COMPANY: NRC FAX NUMBER: (612) 828-8280
ATTENTION: Document Control Desk SENDER: Jerry Edwards
FAX NUMBER: (301) 816-5151 PHONE NUMBER: (612) 828-3951
SUBJECT:
 
CC: Rosemount Nuclear Instruments

Rosemount Nuclear Instruments, inc.
12001 Technology Drive
Eden Prairie, MN 55344 USA
Tel 1(812) 828-8252
Fax 1(812) 828-8280

9 December 1998

Re: Notification under 10 CFR Part 21 for Rosemount Model 710 Trip Unit

Pursuant to 10CFR Part 21 Paragraph 21.21 (b), Rosemount Nuclear Instruments, Inc, (RNII) is writing to inform you of a potential deviation related to certain 710DU0TT 4-20 mA master trip units. A jumper wire (J1) may be incorrectly installed on the circuit card assembly (CCA) of the master trip units. This jumper should only be installed on the CCA's of Model 710DU0TS slave trip units. This jumper bypasses a buffer circuit that serves to protect the 1-5 volt bus of the master trip unit from electrical faults on a slave unit(s). This circuit configuration places the master trip unit in an unqualified (untested) condition and may expose the master trip unit to an unanalyzed failure mode.

References:
1) Schematic Diagram, Fig 21, 710 Service Manual (MAN 4471-2, October 1987) Included as Attachment A
2) Circuit Card Assembly Schematic, Fig 13, 710 Service Manual (MAN 4471-2. October 1987) Included as Attachment B

1.0 Name and address of the individual providing the information:

Mr. Jeffrey W. Schmitt
Vice President & General Manager
Rosemount Nuclear Instruments, Inc.
12001 Technology Drive
Eden Prairie, MN 55344

2.0 Identification of items supplied

Certain Model 710DU0TT master trip units identified in Attachment C.

3.0 Identification of firm supplying the item:

Rosemount Nuclear Instruments. Inc,
12001 Technology Drive
Eden Prairie, MN 55344

4.0 Nature of the failure and potential safety hazard:

Presence of the J1 jumper does not necessarily affect the Analog to Slave Output Signal (Ref 1, Pin 12) since the bypassed circuitry is a unity gain buffer and would supply the same voltage to Pin 12 as the jumpered circuit under normal operating conditions. However. since the buffer is bypassed when the jumper is installed, (Ref 1, Note 14. and Ref 2) the 1-5 volt bus on the master trip unit is not protected from transient conditions that could possibly exist in the slave unit. This condition may introduce an added failure mode of the master trip unit should abnormal circuit conditions in a slave unit be fed back through Pin 12, bypass the buffer circuit via the jumper, and potentially lead to false master trip unit outputs. RNII does not have sufficient information to determine the safety impact related to plant applications. Licensees must determine the impact on plant operations and plant safety and take action as deemed necessary.

5.0 The corrective action which is taken, the name of the individual or organization responsible for that action and the length of time taken to complete that action:

The manufacturer of the CCA used for the 710DU0TT master trip unit has been notified and process changes to preclude this jumper installation on the master trip unit will be implemented immediately. Verification of proper configuration for the CCA will be accomplished by in-circuit testing on an on going basis.
The 710DU0TT master trip units identified in Attachment C should be inspected for presence of the J1 jumper (See figure of Ref 2 for jumper location). If installed, one of the following courses of action must be taken:
1) Return the unit to Rosemount Nuclear Instruments Inc. for jumper removal.
2) Contact Rosemount Nuclear Instruments Inc. to obtain an approved Rework Procedure. Use this procedure to remove the jumper and verify master trip unit functionality.
No further action related to this issue is expected. Mr. Schmitt is responsible should any further action related to this issue be necessary.

6.0 Any advice related to the potential failure of the item:

The end user must determine the full scope of this deviation as it relates to plant operations and plant safety and take action as deemed necessary,
Rosemount Nuclear Instruments, Inc. has a strong commitment to the nuclear industry and assures you that we are dedicated to the supply of high quality products and services to our customers. We are sorry for any inconvenience. If there are any questions, or you require additional information related to this issue, please contact Jerry Edwards (612) 828-3951, Mike Dougherty at (612) $28-5626 or Gerard Hanson at (612) 828-3480.
Sincerely,

ROSEMOUNT NUCLEAR INSTRUMENTS, INC.

Jeffrey W. Schmitt
Vice President & General Manager

FISHER-ROSEMOUNT


Attachment A: Schematic Diagram

Figure 21, 710 Service Manual

(MAN 4471-2, October 1987)

Figure 21. "Schematic Diagram - 710DU Master/Slave Trip Unit (4-20 mA Input). omitted.


Attachment B: Circuit Card Assembly Schematic

Figure 13, 710 Service Manual

(MAN 4471-2, October 1987)

Figure 13, Master Trip Unit (4-20 mA Input) - Circuit Card Assembly." omitted.


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