ML18158A528
ML18158A528 | |
Person / Time | |
---|---|
Issue date: | 06/07/2018 |
From: | Steve Jones NRC/NRR/DSS/SCPB |
To: | |
Jones S, NRR/DSS/SCPB, 415-2712 | |
References | |
Download: ML18158A528 (24) | |
Text
EPRI Hoisting, Rigging and Crane User Group Presentation:
Control of Heavy Loads Steve Jones, Senior Reactor Systems Engineer Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission June 13, 2018 1
Purpose
- Communicate background information regarding existing licensing basis for control of heavy loads
- Communicate operating experience important to NRC regulation and interface with industry initiative activities
- Discuss relationship with ASME Cranes for Nuclear Facilities Committee 2
Heavy Load Issue Timeline GL 85-11 GSI-186 RIS GL81-07 Two Yellow Violations Opened 2008-28 RIS for Stator Drop GL 80-113 2005-25 Closure of GSI-186 Bulletin 96-02 Stator Drop NUREG 0612 and Temp Rig NUREG-1774 NUREG-0554 (Operating Collapse Task A-36 Experience)
ASME Issues NOG-1 ASME Issues Reactor Vessel Comparison Matrix Crane O&M First Dry Fuel Storage Head Lift Issues Standard?
Installation Licensed Industry Initiative 3
Analysis of Issue
- Task A-36:
- Analyze current licensing criteria
- Analyze measures that ensure safe handling of heavy loads.
- Recommend changes
- NUREG-0612 (July 1980)
- Overview of potential consequences of a load drop
- Summary of current licensee programs
- Review of Historical Data
- Guidelines and Recommendations
- Procedures and safe load paths
- Consistency with industry standards
- Assurance that critical SSCs adequately protected 4
Heavy Load Handling Program
- Licensees review heavy load programs against NUREG-0612 guidelines
- Requested responses in two phases to determine how NUREG-0612 guidelines would be met 5
Phase I and II Guidelines:
- Phase I [prevention]:
- Phase II [protection or
- Safe load paths consequence analysis]:
- Load handling procedures - Stops or interlocks prevent
- Periodic inspection and testing movement of load over critical
- Operator qualification SSCs, OR;
- Lifting device standard - Overhead crane and lifting devices designed to be single
- Sling standard failure proof, OR;
- Crane design standard - Load drop analyses
- Interim Technical Specifications demonstrate acceptable consequences.
6
Review of Phase I and II
- All licensees submitted Phase I and II information
- Resource intensive reviews confirmed conformance with Phase I guidelines
- Phase II responses sampled
- Phase II responses generally enhanced Phase I implementation through limited load drop analyses and administrative controls (where single-failure-proof cranes were not installed) 7
Resolution of Phase II (GL 85-11)
- Greatest risk - heavy loads over irradiated fuel
- Risk to safe-shutdown systems considered small
- Full implementation of Phase II unjustified
- Phase II responses did not identify additional concerns; no need for further generic action
- However, Phase II responses captured in licensing basis 8
- Handling of dry storage casks began after establishment of heavy load programs
- Bulletin initiated because of proposed movement of dry storage casks at power in a BWR
- Potential for cask drop to initiate transient and damage key equipment
- Reinforced requirement to evaluate changes in operations through safety analysis report change process (10 CFR 50.59) 9
Heavy Load Generic Issue
- Generic Issue 186 was opened in 1999 to determine the need for more regulatory action
- Operating experience review published as NUREG-1774
- RIS 2005-025 in October 2005 and Supplement in May 2007 reemphasized expectations regarding heavy load handling
- Identified focus areas based on operating experience 10
Operating Experience Findings
- Most heavy lift accidents due to below the hook issues (human errors, rigging failures, etc.) vice crane deficiencies
- Industry standard provides clear single failure proof criteria for cranes
- Consequence and load drop analysis methodologies vary between licensees
- Three >30 ton load drops between 1980 and 2002, all due to rigging failures (not crane failures) 11
Key Insights
- Three recurring causes of load drops at nuclear power plants:
- Two-blocking
- Intermediate hoists
- Inadequate sling protection
- Human performance important to prevention
- Additional measures can reduce risk
- Limit height of lift
- Redundant equipment available
- Use specially designed lift rigs 12
Two Blocking
- Three drops due to cutting of wire rope
- 1970-Palisades (Polar Crane Aux Hoist; Prior to Operation; Limit Switch Bypassed)
- 1985-Browns Ferry (Unloaded Turbine Aux Hoist)
- 1993-Calvert Cliffs (Unloaded Turbine Aux Hoist)
- Relationship to nuclear safety
- Aux hoist faster than main hoist; less time for operator action
- Main hoists carry heaviest loads
- Two Blocking is a credible cause of load drops 13
Intermediate Hoists
- Hoist failure - Comanche Peak - 1999
- 20 foot drop of 45 ton motor
- Snag avoided RCS impact
- Plant was defueled
- Chain failure - Peach Bottom - 2002
- 10 inch drop of 24 ton motor
- No damage to RCS; fuel in vessel
- Load path issue - South Texas - 2003
- 50 ton motor moved over operating RHR heat exchanger (in containment)
- Double-capacity lift rig specified in heavy load program not used 14
Intermediate Hoists (Continued)
- Relationship to nuclear safety
- Intermediate hoist increases failure probability
- Failures could threaten decay heat removal
- Regulatory Insights
- Not addressed in heavy load guidelines
- Redundant capabilities unaffected by potential load drop should be available to manage risk pursuant to 10 CFR 50.65(a)(4) 15
Slings
- Three drops of very heavy loads
- 2001 at San Onofre (mobile crane dropped from turbine bldg crane)
- 2001 at Turkey Point (mobile crane dropped form turbine bldg crane)
- 2005 at Browns Ferry (old trolley dropped from reactor building crane temp hoist)
- All outside scope of heavy load program 16
Slings (Continued)
- Nuclear safety insights
- Failed slings used in basket configuration
- Slings used as part of cask lifting device with special fittings
- Operating experience suggests synthetics more susceptible to cutting than steel
- Training and procedures may improve identification of incorrect sling usage
- Steel slings may allow more time to correct inadequate corner softening 17
Continued Heavy Load Issues
- Mid-2000s: refueling delays
- Regulatory Issue: unclear licensing bases (particularly reactor head lifts)
- Safety Issue: potential damage that precludes adequate cooling of irradiated fuel
- Desired Resolution: improved practices aligned with licensing basis 18
Industry Initiative
- NEI proposed industry initiative related to heavy load handling:
- Safety basis for key heavy lifts
- Safety basis incorporated in FSAR
- Develop industry guidance for reactor head lifts (load drop analyses and single-failure-proof crane equivalence)
- Enforcement discretion during implementation
- NRC held public meetings with NEI to speed guideline development 19
Industry Guidelines (NEI 08-05)
- Realistic reactor head drop analysis methodology
- Single-failure-proof handling system equivalence for head lifts
- Maintenance rule risk management
- NRC staff endorsed the NEI guidelines, with some exceptions 20
Safety Significance
- PWR Head Lifts
- Significant portion of lift at height/location where drop could severely damage vessel
- High lift - increased potential for two-blocking, an important cause of drops
- Crane inspection/maintenance on or near critical path
- Vulnerable to single failures/operator error
- BWR Cask Movements
- Potential for drops from high elevations over sensitive structures (e.g., spent fuel pool floor and torus)
- Often performed with reactor operating at power 21
Load Drop Probabilities
- NUREG-0612, 1980 (Navy Data):
6.3 E-05 Drops/Lift
- NUREG-1774, 2003 (>30 Ton Lifts):
5.6 E-05 Drops/Lift
- DOE WIPP Study
- Crane Failure (Navy Data):
2.5 E-06 Failures/Lift
- Human Error Probability (Failure of Lifting Device):
8 E-07 Failures/Lift
- Estimates uncertain due to limited data 22
- Collapse due to buckling of unstable column assembly
- New configuration
- Not load tested
- Adverse impacts
- Loss of electric power
- Trip of adjacent unit
- Flooding
- Safety Significance
- Mechanical damage and flooding impacted all sources of AC power except EDGs
- Unit 1 EDG work not coordinated with stator move 23
Ongoing Activities
- Policy is to endorse consensus standards where appropriate
- Participation with ASME for standards development
- ASME NOG-1, 2010 and later include matrix to NUREG-0554 guidelines for single failure proof cranes
- ASME HRT-1 addressed heavy component replacement activities following ANO stator drop
- ASME developing operation and maintenance standard addressing scope of NUREG-0612
- Inspection and licensing
- Consolidated interim fuel storage license application
- At-reactor independent fuel storage facilities
- Reactor refueling activities 24