ML20128G922
| ML20128G922 | |
| Person / Time | |
|---|---|
| Site: | Clinton  |
| Issue date: | 10/03/1996 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20128G919 | List: |
| References | |
| NUDOCS 9610090173 | |
| Download: ML20128G922 (4) | |
Text
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UNITED STATES p*
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,j NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20666-0001 o
,o SAFETY EVALUATION BY THE OFFICE OF NVCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO.107 TO FACILITY OPERATING LICENSE NO. NPF-62 ILLIN0IS POWER COMPANY. ET AL.
CLINTON POWER STATION. UNIT NO. 1 DOCKET NO. 50-461
1.0 INTRODUCTION
By letter dated June 28, 1996, and as supplemented by letter dated September 17, 1996, Illinois Power Company, the licensee, requested a revision to Facility Operating License No. NPF-62 for the Clinton Power Station. The proposed amendment would permit removal of the Inclined Fuel Transfer System (IFTS) primary containment blind flange while primary containment integrity is required. This modification to the Clinton Power Station Technical Specification (TS) Surveillance Requirement 3.6.1.3.3, associated with TS 3.6.1.3, " Primary Containment Isolation Valves (PCIVs)," will provide flexibility to operate the IFTS for the purpose of testing and exercising the system prior to a refueling outage.
2.0 BACKGROUND
The Mark III containment design of the Clinton Power Station includes an upper pool in the containment building. The spent fuel pool is physically located at a lower elevation in the adjacent Fuel Building.
During refueling outages, an inclined fuel transfer system (IFTS) is used to transfer fuel, control rods, defective fuel storage containers and other small items between the upper containment pool and the spent fuel pool. The IFTS includes a 23-inch ID stainless steel transfer tube enclosing a carriage that is used for transport. The IFTS is a fixed installation, consisting of the inclined fuel transfer tube, upper and lower upenders, valves at both ends of the fuel transfer tube, a carriage equipped with a calibrated positioning system, an electrically powered winch, a primary containment isolation assembly, and supporting instrumentation.
The IFTS penetrates primary containment and connects the containment and fuel building. The top end of the IFTS is located at the bottom of the containment building fuel transfer pool and is normally sealed by a 24-inch flap valve.
Located just inside of the containment liner is a containment isolation assembly consisting of a manual gate valve, containment bellows, and a primary containment blind flange. The blind flange is installed during operating modes 1, 2, and 3 when containment integrity is required to be maintained.
The blind flange establishes containment isolation and prevants movement of the carriage between containment and the fuel building. The bottom end of the 9610090173 961003 PDR ADOCK 05000461 P
. IFTS is fitted with a 24-inch gate valve and is located approximately 25 feet below the surface of the fuel building fuel transfer pool.
The IFTS is a complex system that remains idle during normal plant operation and is only used to support refueling activities. Once the plant is shutdown and containment integrity is no longer required, the licensee is allowed to loosen the containment bellows and remove the primary containment blind flange. System operation (from the top) is initiated by the upper pool upender in the containment building fuel transfer pool tilting the fuel to align with the fuel transfer tube. The 24-inch flap valve is opened and the fuel travels on the carriage within the transfer tube. After the carriage travels almost the entire length of the transfer tube, it stops within two feet of the bottom gate valve. At this point, the upper 24-inch flap valve is closed and the transfer tube is drained of water by opening both a 4-inch vent j
line (which opens to the containment atmosphere) and a separate 4-inch drain line that leads to the fuel pool cooling and cleanup system surge tank. The drain line has both a motor-operated and manual isolation valve in series.
When the transfer tube is drained, the remaining head of water in the tube is equal to the height of water in the fuel building fuel transfer pool.
The lower 24-inch gate valve is then opened allowing the carriage to travel to the lower pool upender where the fuel is uprighted for long-term storage.
System l
operation initiating from the bottom is similar except that once the carriage enters the transfer pool and the bottom 24-inch gate valve is closed, a fill valve and the vent valve are opened to flood the transfer tube.
The IFTS system is maintained in an idle condition for up to 18 months between refueling outages. Due to containment isolation requirements, the licensec is prohibited from removing the blind flange during operating modes 1, 2, and 3 to test and inspect the system. During previous refueling outages, the licensee has experienced significant operational difficulties with the IFTS.
This has resulted in IFTS start-up operations becoming " critical path" activities.
The licensee has indicated a desire to inspect and exercise the IFTS prior to operating it in continuous duty during a refueling outage. Therefore, by letter dated June 28, 1996, the licensee proposed a modification to the Clinton Power Station Technical Specifications that would permit them to remove the primary containment blind flange of the IFTS during plant operations in order to make NCessary Component adjustments and demonstrate system operation. This submittal was supplemented by a September 17, 1996, response to a staff request for additional information.
The licensee has i
proposed inserting a note to Surveillance Requirement 3.6.1.3.3, associated with Technical Specification 3.6.1.3, " Primary Containment Isolation Valves (PCIVs)." The note specifies those conditions when the IFTS blind flange could be removed during operating modes 1, 2, and 3.
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. 3.0 EVALUATION Surveillance Requirement (SR) 3.6.1.3.3, associated with Technical Specification 3.6.1.3, " Primary Containment Isolation Valves (PCIVs)" states that the licensee shall:
Verify each primary containment isolation manual valve and blind flange that is located inside primary containment, drywell, or steam tunnel and is required to be closed during accident conditions is closed.
The Frequency of the above SR is " Prior to entering MODE 2 or 3 from MODE 4, if not performed within the ptevious 92 days."
The licensee has proposed inserting the following note to SR 3.6.1.3.3:
Not required to be met for the Inclined Fuel Transfer System (IFTS) penetration when the associated primary containment blind flange is removed, provided that the fuel building fuel transfer pool water level is maintained 2 el. 753 ft. and the IFTS transfer tube drain valve (s) remain (s) closed, except that the IFTS tube drain valve (s) may be opened under administrative controls.
The licensee has identified an alternate means to ensure isolation of the IFTS containment penetration in lieu of having the IFTS blind flange in place.
This alternate means takes credit for the fact that the IFTS transfer tube terminates deep in the fuel building fuel transfer pool, effectively sealing the tube and precluding it from becoming a potential leak path of the containment atmosphere (into the fuel building) in the event of a design basis accident.
The licensee has identified two scenarios where leakage from a design basis accident would be a concern when the blind flange is removed. The first scenario involves a design basis accident with the fuel transfer tube drained down to the drain line. The peak calculated containment internal pressure for the design basis loss of coolant accident (P is 9.0 psig.
Following a postulated accident,. containment atmosphere w,)ould travel directly through the 4-inch vent pipe to the water level in the fuel transfer tube. As previously stated, the water level in the fuel transfer tube would not go below the level of the fuel building fuel transfer pool. The peak calculated containment internal pressure, P is equivalent to a head of water of 21.7 ft. A review of as-built drawings,, indicate that the normal water level elevation in the fuel building fuel transfer pool is 754'0".
Considering that the 24-inch gate valve located at the bottom of the fuel transfer tube is located at elevation 728.9 ft, containment atmosphere would have to displace the equivalent of 25.1 ft (i.e., 754 - 728.9 ft).
This exceeds the equivalent head created by the l
l design basis accident by 3.4 ft. The proposed note in SR 3.6.1.3.3 will require a minimum water level elevation of 753 ft which will result in a l
minimum margin of 2.4 ft of water. Therefore, the staff concurs that l
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. containment atmosphere leakage through the length of the fuel transfer tube is not plausible.
The second scenario described by the licensee is containment atmosphere leakage past the open drain line directly to the fuel pool cooling and cleanup surge tank. As previously described, the two valves in this 4-inch drain line must be opened to drain the fuel transfer tube before opening the bottom 24-inch gate valve.
If a design basis loss of coolant accident occurs with these drain valves open, containment atmosphere could go directly through the 4-inch vent pipe, down the fuel transfer tube, down the drain line, to the surge tank. As described in the proposed note to SR 3.6.1.3.3, the drain valves will only be opened under administrative controls. The licensee's letter of September 17, 1996, describes the proposed administrative controls. A description of the administrative controls is also included in a proposed revision to the technical specification bases included in this letter. The individual at the IFTS controls in the fuel building, who is in continuous communication with the control room, will be responsible for remotely closing the automatic drain valve (IF42-F003) from the IFTS controls. The individual will then leave this station and locally close the associated manual valve (1F42-F301) using the gear operator mounted on top of the valve.
In this way, the penetration can be rapidly isolated.
In addition, the time that the drain valve would be open will be minimized.
The staff is familiar with past problems that the licensee has experienced with the IFTS. According to the licensee's submittal, a satisfactory check of the entire IFTS, including any subsequent adjustment of sensors or system repairs, can take several days.
Therefore, the licensee would likely be performing such testing and inspections of the IFTS during the last few weeks prior to a planned refueling outage. The staff considers the licensee's justification to be reasonable.
In response to a staff question, the licensee's letter of September 17, 1996, stated that "since potential air leakage pathways are either water sealed or can be rapidly isolated, a release to the Fuel Building atmosphere that could affect the ability of personnel to perform other safety functions associated with mitigating a postulated LOCA, or prevent them from maintaining the plant in a safe condition during or following a LOCA, would not be expected." The staff further notes that even if containment atmosphere enters the fuel building, it would be contained within the boundaries of the secondary containment and filtered by the Standby Gas Treatment System prior to release to the environment.
Therefore, based on the information described above, the staff finds the license's proposal acceptable.
4.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Illinois state official
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was notified of the proposed issuance of the amendment.
The state official had no comments.
5.0 ENVIRONMENTAL CONSIDERATION
This ainendment changes a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 or changes a surveillance requirement. The NRC staff has determined that the amendment involves no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative i
occupational radiation exposure. The Comission has previously issued a proposed finding that the amendment involves no significant hazards consideration and there has been no public comment on such finding (61 FR 40021). Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendment.
5.0 CONCLUSION
The staff has concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such j
activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributors: Douglas V. Pickett Richard M. Lobel Date: October 3, 1996 l
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