05000461/FIN-2009004-04
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Finding | |
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| Title | RPV Head Strongback, Dryer/Separator Strongback and RPV Head Lifting Lugs Did Not Demonstrate Single Failure Proof Requirements of NUREG 0612, Control of Heavy Loads at Nuclear Power Plants, Section 5.1.6 |
| Description | The inspectors identified an Unresolved Item concerning whether the design of the RPV head strongback, dryer/separator strongback and RPV head lifting lugs was in conformance with the licensing and design basis for single failure proof requirements of NUREG 0612, Section 5.1.6. Specifically, the RPV head strongback, dryer/separator strongback and RPV head lifting lugs did not meet design factors of safety versus yield and ultimate strengths consistent with the guidelines of NUREG 0612, Section 5.1.6. The inspectors reviewed the following licensee submittals: 1. Illinois Power Letter U-0249 L30-81 (06-19)-L to NRC, Subject: December 22, 1980, letter on Control of Heavy Loads, June 22, 1981; 2. Illinois Power Letter U-0294 L30-81 (09-25)-L to NRC, Subject: Clinton Power Station Units 1 and 2 Docket Nos. 50-461 and 50-462, September 25, 1981; 23 Enclosure 3. Illinois Power Letter U-06850982-L L30-83 (12-21)-L to NRC, Subject: Clinton Power Station Unit 1 Control of Heavy Loads (NUREG-0612), December 21, 1983; and 4. Illinois Power Letter U-0800 L30-85(02-21)-6 B48-85(02-21)-6 1A.120 to NRC, Subject: Clinton Power Station Unit 1 Control of Heavy Loads (NUREG-0612), February 21, 1985. As a result of this review, the inspectors identified several assurances from the licensee that the RPV head strongback, dryer/separator strongback and RPV head lifting lugs were in conformance with the single failure proof requirements of NUREG 0612, Section 5.1.6. The letter dated June 22, 1981, identified the RPV head strongback and dryer/separator strongback as carrying heavy loads such as the RPV head, drywell head, steam dryer and steam separator over safety-related equipment. The licensee had evaluated the hazard of either of the RPV head strongback or dryer separator being dropped as a heavy load over safe shutdown equipment and determined the likelihood of handling system failure for this load is extremely small (i.e., Section 5.1.6 NUREG 0612 satisfied). The letter dated September 25, 1981, responded to an NRC request to provide an evaluation of the lifting devices for each single-failure-proof handling system with respect to the guidelines of NUREG 0612, Section 5.1.6. The licensees response was that the two lifting devices are currently anticipated to be used to accomplish lifts with the polar crane over the refueling floor. Both are supplied by General Electric. They are the steam separator/dryer strongback and the RPV head carousel strongback. Each strongback is provided with four lift points to the load. General Electric states that two of the four attachments are capable of supporting the load. A single failure is considered as the loss of one lift point only. The strongbacks are attached to the polar crane redundant sister hook through the use of a hook box on top of the strongbacks and through two six-inch-diameter link pins. General Electric terms the strongbacks single-failure proof. The letter dated September 25, 1981, responded to an NRC request to provide an evaluation of the interfacing lift points with respect to the guidelines of NUREG 0612, Section 5.1.6. The licensees response was that the four lifting lugs are used on the RPV head. After failing two lugs, each of the remaining two lugs would have to support 63,100 pounds. These two remaining lugs are assumed to be opposed on the head so that the head would remain level. Based on a tensile strength of 80,000 psi and a cross-sectional analysis on the lug only 18 inches squared, the remaining two lugs in cross-section have a design margin of approximately 22. The cross-sectional area above also applies to the steam separator and the steam dryer lugs. The letter dated December 21, 1983, responded to an NRC request, which stated that the dryer/separator strongbacks load test does not meet the formal requirements of a 150 percent test. The 125 percent load test may be acceptable, however, more information should be provided. Basically, if the device is Single-Failure-Proof, a description of the device and the meaning of the load test is needed. If the device isnt Single-Failure-Proof, the device description should be accompanied by a discussion of potential load drop consequences. The licensees response was that the strongback will be upgraded to a factor of safety of ten in compliance with Section 5.1.6(1a), Single Failure Proof Handling Systems, of NUREG-0612. The letter dated February 21, 1985, responded to an NRC request to confirm the actual number of special lifting devices. Verify that each meets American National Standards Institute (ANSI) N14.6-1978 and all are designed for static plus maximum dynamic loads. The licensees response was two special lifting devices will be used at Clinton, the RPV head strongback and the RPV dryer/separator strongback, both of which have been designed and supplied by General Electric to accomplish their intended reactor vessel servicing and refueling functions. Both strongbacks are designed to be single failure proof and should adequately comply with NUREG 0612, Paragraph 5.1.1(4). The inspectors were concerned that the RPV head strongback, dryer/separator strongback and RPV head lifting lugs did not meet design factors of safety versus yield and ultimate strengths consistent with the guidelines of NUREG 0612, Section 5.1.6. In order to meet the intent of NUREG 0612, Section 5.1.6, the following design factors were satisfied: (a) Provide redundancy or duality such that a single lift point failure will not result in uncontrolled lowering of the load; lift points should have a design safety factor with respect to ultimate strength of five times the maximum combined concurrent static and dynamic load after taking the single lift point failure. Additionally, the device should have a design safety factor with respect to yield strength of three after taking the single lift point failure; or (b) a non-redundant or non-dual lift point system should have a design safety factor of ten times the maximum combined concurrent static and dynamic load. Additionally, the device should have a design safety factor with respect to yield strength of six. If the design factors were not satisfied, these guidelines require that entire heavy load path be analyzed for a heavy load drop and the results show that dropping a heavy load such as the RPV head, drywell head, steam dryer and steam separator did not create an unacceptable risk. The intent was to ensure safe handling of heavy loads in areas where a load drop could impact fuel in the reactor core, or equipment that may be required to achieve safe shutdown or permit continued decay heat removal. In response to the concern, the licensee initiated AR 00938280 on July 2, 2009. This issue is considered an Unresolved Item (URI 05000461/2009004-04) pending additional inspector discussion with the Office of Nuclear Reactor Regulation staff to determine licensing basis requirements for Clinton Power Station, specifically whether these lifting devices needed to meet NUREG 0612 Section 5.1.6 |
| Site: | Clinton  |
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| Report | IR 05000461/2009004 Section 1R20 |
| Date counted | Sep 30, 2009 (2009Q3) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.2 |
| Inspectors (proximate) | A Scarbeary B Kemker D Lords J Bozga M Mitchell M Ring S Mischke |
| INPO aspect | |
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Finding - Clinton - IR 05000461/2009004 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Clinton) @ 2009Q3
Self-Identified List (Clinton)
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