05000321/LER-2004-002
| Edwin I. Hatch Nuclear Plant - Unit 1 | |
| Event date: | 2-24-2004 |
|---|---|
| Report date: | 4-23-2004 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3212004002R00 - NRC Website | |
DOCKET
05000-321 LER NUMBER (6
PLANT AND SYSTEM IDENTIFICATION
General Electric - Boiling Water Reactor Energy Industry Identification System codes appear in the text as (EIIS Code XX).
DESCRIPTION OF EVENT
On 2/24/2004 at 1730 ET, Unit 1 was in the Refueling mode. At that time, an investigation of the As Found Local Leak Rate Test (LLRT) failures on five of the twelve suppression chamber to drywell vacuum breakers' air actuators (replaced during the spring 2002 refueling outage) determined that the internal seal arrangement had been changed. This change resulted in the deletion of the inboard primary containment isolation barriers (EIIS JM) for this penetration.
During the spring 2002 refueling outage, all twelve of the Unit 1 suppression chamber to drywell vacuum breakers air actuators (manufactured by Hiller) were replaced with new actuators. The actuators being replaced were dual acting actuators which had two internal seals located on the piston enabling the piston to be driven in either direction depending on the location of the air supply (see attached figure). The actual installation of these actuators at the plant relied on air for moving the piston in only one direction. The air supply moved the piston in a direction that would open the vacuum breaker. The plant installation relied on an internal spring in the actuator to return the piston after the air was isolated thereby allowing the vacuum breaker to close. The unused air supply connection is vented to the primary containment atmosphere inside the torus. Therefore, although the plant did not rely on one of the seals for moving the piston within the actuator, the plant did rely on this seal for a primary containment isolation barrier. Because of previous problems with the vacuum breaker closed position indication not picking up when cycling the vacuum breakers for the required 31 day functional test, these new actuators were being changed to use a heavier return spring. During the change process to install the heavier springs, the vendor increased the length of the actuator. The lengthening of the actuator created an interference with other plant equipment and the new actuators were returned to the vendor to be shortened. In order to shorten the actuators, the vendor reworked the piston seal arrangement and eliminated the seal being relied upon for a primary containment isolation barrier.
A successful LLRT was performed after the installation of these new actuators during the spring 2002 refueling outage. Discussions with the vendor concerning the successful results of this LLRT concluded that they passed because of the close tolerance fit of the piston in the new actuators along with the lubricating oil applied to the piston. A review by the plant concluded that the method of testing this barrier is acceptable and that it adequately simulates the conditions for which primary containment is designed. Although it can not be positively determined when the primary containment barrier would have failed to meet its ability to isolate primary containment atmosphere, it most likely did occur sometime early in the operating cycle (on 4/18/2002 at 1226 ET the plant entered mode 2 from the spring 2002 refueling outage) after stroking the vacuum breakers several times.
FACILITY NAME (1) DOCKET � LER NUMBER (6 PAGE (3) A review of procurement and design documentation was performed concerning this change to the actuators. This review determined that:
1) Information concerning the change to the design of the piston actuator assembly was not incorporated into the procurement documents governing the purchase of the actuator assemblies, and 2) What was ultimately shipped to the site by the vendor was not in accordance with the provisions of the original purchase order, and 3) The planes design records did not clearly describe the primary containment isolation barrier function for this actuator, in that design assembly drawings were not available to the plant staff depicting the required dual seal arrangement. Thus, the focus of the change was on the requirement for the heavier spring. An Equivalency Determination (ED) was performed for the new actuators but this ED only addressed the change to a heavier spring.
A review of the Unit 2 air actuators determined that they are made by a different manufacturer and do not have this problem.
CAUSE OF EVENT
The cause of the event was that design records did not clearly specify the dual seal arrangement of the component being purchased. The focus of the change was therefore on the need for a heavier spring and, consequently, there was insufficient information for the vendor to understand that the second seal was a required design feature for these actuators. Thus, the vendor eliminated the second seal and, as a consequence, the primary containment isolation barrier.
REPORTABILITY ANALYSIS AND SAFETY ASSESSMENT
This report is required by 10 CFR 50.73(a)(2)(i)(B) because a condition existed that was prohibited by the planes Technical Specifications in that the actions required by TS LCO 3.6.1.3 for a failed PCIV were not taken. Although the actuator seal is not a valve and the LLRT testing performed for this device is a type `1 test, the TS Bases background for LCO 3.6.1.3 states that, with respect to PCIVs, `these isolation devices are either passive or active (automatic):' Examples of passive devices include closed systems and blind flanges. Based on the examples of passive devices that are listed, it is concluded that this actuator seal meets the intent of a PCIV passive device.
Unit 1 FSAR 5.2.2.5.4.2 states, in part, that these twelve lines penetrate the torus shell to supply air to piston operators on the vacuum breaker valves. These lines meet the requirements of Safety Guide 11, since they do not penetrate the RCPB and do not open to the primary containment atmosphere. One solenoid valve for each line is located close to the penetration outside the torus shell. The valves are manually controlled from the MCR. With this seal absent in these actuators, the lines would in fact communicate with the primary containment atmosphere.
DOCKET
05000-321 LER NUMBER (6 In this event, because all of the outboard PCIVs associated with these actuators successfully passed their as found LLRT this outage, the minimum-pathway leakage for each of these penetrations was acceptable throughout the operating cycle. Additionally, the outboard PCIVs remained closed throughout the cycle except to perform the required TS Surveillance (SR) 3.6.1.8.2. This SR calls for performing a functional test of each required vacuum breaker every 31 days. If the outboard PCIV would have been inadvertently left open, then the associated vacuum breaker would have opened and Hatch Unit 1 would have been required to enter TS LCO 3.6.1.8, Condition B which requires the vacuum breaker to be closed within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />. Therefore, all of the actions required by the TS action for an INOPERABLE PCIV were met with the exception of the requirement to deactivate (i.e., pulling a fuse) the outboard PCIVs. Because the outboard PCIVs were maintained closed with the exception of opening them for required TS surveillance testing it may be concluded that this event did not adversely impact nuclear safety or the health and safety of the public and did not represent a substantial safety hazard.
CORRECTIVE ACTIONS
All of the twelve suppression chamber to drywell vacuum breakers air actuators were rebuilt during the spring 2004 refueling outage to install the two internal seals restoring the inboard primary containment isolation barrier. These rebuilt actuators all successfully passed LLRT.
A statement has been added to the existing standard procurement paragraph which discusses vendor notifications of exceptions and changes to items. The statement clarifies that if a vendor is required to make additional changes to an item, these changes will be approved by Southern Nuclear prior to shipment of the item, and that the vendor not ship items which do not agree with the requirements/description stated in the purchase order.
Following discussions between the vendor and the plant staff, a detailed design drawing was obtained from the vendor depicting the configuration of the replacement actuator and actuator seals. This drawing has been associated with the plant equipment via the planes configuration control procedures.
ADDITIONAL INFORMATION
No systems other than those previously described in this report were affected by this event.
This LER does not contain any permanent licensing commitments.
There were no previous similar events reported in the past two years in which the plant entered a condition prohibited by Technical Specifications as the result of design and procurement records not clearly depicting the required configuration of the component being purchased.
FACILITY NAME (1) DOCKET LER NUMBER (6 PAGE (3) Edwin I. Hatch Nuclear Plant - Unit 1 05000-321
FAILED COMPONENT INFORMATION:
Master Parts List: 1T48-F323A-L Manufacturer: Hiller Manufacturer Code: H198 Model Number: 2 /2 SA-A041 Type: Air Cylinder / Coil Spring Actuator EIIS System Code: JM EIIS Component Code: ISV Root Cause Code: B Reportable to EPIX: Yes AMIEVAIVIIMPAIWAWAIIIIYAMVAINP21111IAINFAIIIIIIIIIIIVIIIIIIIA111211112111/21111151111112111/411reFir41111/41110 Leakage Path Air connection vented to containment Outside Containment Containment Directional Seal for air supply Spring to return piston to rest position Piston actuating rod for vacuum breaker testing Sectional view of vacuum breaker actuator Shorter Piston and Containment Seal Missing