05000440/LER-2006-002, Regarding Scaffold Built in the Containment Pool Swell Region

Regarding Scaffold Built in the Containment Pool Swell Region

ML060940641
Person / Time
Site:	Perry
Issue date:	03/24/2006
From:	Pearce L FirstEnergy Nuclear Operating Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
PY-CEI/NRR-2946L LER 06-002-00
Download: ML060940641 (5)

LER-2006-002, Regarding Scaffold Built in the Containment Pool Swell Region

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(ii) 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
4402006002R00 - NRC Website

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FENOC, FirstEnergy Nuclear Operating Company Perry Nuclear Power Station 10 Center Road Perry Ohio 44081 L. Wlliam Pearce Vice President 440-280-5382 Fax: 440-280-8029 March 24, 2006 PY-C:EI/NRR-2946L United States Nuclear Regulatory Commission DoCLment Control Desk Washington, DC 20555 Perry Nuclear Power Plant Docket No. 50-440 Ladies and Gentlemen:

Enclosed is Licensee Event Report (LER) 2006-002, Scaffold Built in the Containment Pool Swel Region.

There are no regulatory commitments contained in this letter or its enclosure. Any actions discussed in this document that represent intended or planned actions are described for the NRC's information, and not regulatory commitments.

If there are any questions concerning this matter, please contact Mr. Jeffery J. Lausberg, Manager-Regulatory Compliance, at (440) 280-5940.

Very truly yours, L.W. Pearce Enclcsure: LER 2006-002 cc: NRC Project Manager NRC Resident Inspector NRC Region Ill S

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NRC FORM 3B6 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150-0104 EXPIRES 6/30/2007 (6-2004)

, the NRC may (See reverse for required number of not conduct or sponsor, and a person is not required to rempond to, the digits/characters for each block) information collection.

3. PAGE Perry Nuclear Power Plant 05000440 1 OF IT

4. TITLE Scaffold E;uilt in the Containment Pool Swell Region

5. EVENT DATE

6. LER NUMBER

7. REPORT DATE

8. OTHER FACILITIES INVOLVED SEOUENTIAL REV FACILITY NAME DOCKET NUMBER MONTH DAY YEAR NUMBER NO.

MONTH DAY YEAR 2006 2006 002 000 03 24 2006 FACILITY NAME DOCKET NUMBER

9. OPERATING MODE

11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR 1: (Check all that apply)

El 20.2201(b) 0 20.2203(a)(3)(i)

El 50.73(a)(2)(i)(C)

D] 50.73(a)(28(vii) 1 _

20.2201(d) 0 20.2203(a)(3)(ii) 0 50.73(a)(2)(ii)(a) 0 50.73(a)(2l(viii)(A) 0 20.2203(a)(1) 0 20.2203(a)(4)

S 50.73(a)(2)(ii)(B)

El 50.73(a)(2l(viii)(B) 0E 20.2203(a)(2)(i) 0 50.36(c)(1)(i)(A) 5 50.73(a)(2)(iii) 0 50.73(a)(2)(ix)(A)

10. POWER LEVEL 5 20.2203(a)(2)(ii) 5 50.36(c)(1)(ii)(A) 5 50.73(a)(2)(iv)(A)

S 50.73(a)(2)(x) 0 20.2203(a)(2)(iii) 5 50.36(c)(2) 0 50.73(a)(2)(v)(A) 5 73.71(a)(4I 100%

0 20.2203(a)(2)(iv) 0 50.46(a)(3)(ii) 0 50.73(a)(2)(v)(B)

El 73.71(a)(5) 5 20.2203(a)(2)(v) 5 50.73(a)(2)(i)(A) 5 50.73(a)(2)(v)(C) a OTHER Specify in Abstract below 05 20.2203(a)(2)(vi) 0 50.73(a)(2)(i)(B) 5 50.73(a)(2)(v)(D) or in (If more space is required, use additional copies of NRC Form 366A)

INTRODUCTION

During the investigation of the program used to build scaffolding inside containment it was determined that the current evaluation was not adequate for scaffolding to be erected in the pool swell region. A condition report was written to determine if any past operability concerns existed for scaffolding that had been built within the pool swell region. This analysis was concluded on January 25, 2006 and it determined that scaffolding built on December 8, 2005 and December 28, 2005 with the plant operating in Mode 1 at 100% power was erected in the pool swell region of containment in support of maintenance activities. These scaffold builds were allowed based on engineering seismic evaluation and PSA risk analysis. It was later determined that this analysis was inadequate, and as a result of these reviews, the scaffold installed in the pool swell region placed the plant in an unanalyzed condition with respect to potential hydrodynamic missile hazards in the event of a design basis loss of coolant accident (LOCA).

Following E design basis LOCA in the dry well, the atmosphere is rapidly compressed due to blowdown mass and energy addition to the dry well volume. This compression is transmitted to the water in the weir annulus in the form of a compressive wave which propagates through the horizontal vent system into the suppression pool.

Following vent clearing, the air-steam-water mixture flows from the dry well through vents and is injected into the suppression pool. During vent flow the steam component of the flow mixture condenses in the suppression pool while the air, since it is non-condensable, is released to the suppression pool in the form of high pressure air bubbles. The continued addition and expansion of air within the suppression pool causes the volume to swell resulting in acceleration of the pool surface vertically upwards. The area in containment where this occurs is called the "Dool swell region".

EVENT DESCRIPTION

During the investigation of the program used to build scaffolding inside containment it was determined that the current evaluation was not adequate for scaffolding to be erected in the pool swell region. A condition report was written to d atermine if any past operability concerns existed for scaffolding that had been built within the pool swell region. This analysis was concluded on January 25, 2006 and it determined that scaffolding built Ofl December 3, 2005 and December 28, 2005 with the plant operating in Mode 1 at 100% power was erected in the pool swell region of containment in support of maintenance activities. The initial evaluation concluded that the use of an engineering seismic evaluation and a probability risk assessment without analyzing for pool swell hydrodynamic missile hazards to justify allowing scaffolding to be built in the pool swell region is not acceptable.

The investigation further determined that a review of systems, structures, and components (SSC) operability must be performed and appropriate Technical Specification Limiting Conditions of Operation (LCO) must be entered to allow scaffold builds in the pool. swell region. As a result of the inadequate reviews,tihe icffaId installed ithe pool swell region placed the plant in an unanalyzed condition with respect to potential hydrodynamic missile hazards in the event of a design basis loss of coolant accident. This was determined to be reportable per I OCFR(a)(2!)(ii)(B): Any event or condition that resulted in the nuclear power plant being in an unanalyzed condition that significantly degraded plant safety.

CAUSE OF EVENT

Multiple procedure changes were implemented as a result of 10CFR50.59 rule changes. Based on interpretation of the new 'ule, barriers were removed from existing procedures that prevented scaffold from being built in the pool swell region without proper evaluation. Specifically, procedure changes were implemented that did not require analysis of potential hydrodynamic missile hazards in the event of a design basis loss of coolant accident.

As a result, the necessary assessment of SSC operability was not performed and appropriate Technical Specification LCOs were not entered.U.S. NUCLEAR REGULATORY COMMISSION (1-.2001)

LICENSEE EVENT REPORT (LER)

1. FACILITY NAME

2. DOCKET

6. LER NUMBER

3. FAGE SEQUENTIAL REVISION YEAR NUMBER NUMBER Perry Nuclear Power Plant 05000440 l

U 3 0F 4 2006 002 000

17. NARRATI HE (If more space is required, use additional copies of NRC Form 366A)

EVENT ANALYSIS

Scaffolding built in the containment pool swell region has been analyzed from a Probabilistic Risk Assessment (PRA) perspective and is documented in Calculation PSA-009, Revision 3. This calculation assumes that if a large or intermediate Loss of Coolant Accident (LOCA) were to occur between the time a scaffold is built until it is removed that catastrophic damage would occur to mitigating systems and containment. The consequences of the damage assumed to be incurred by the mitigating systems is core damage and a large early release of radioactivity to the environment. This is a bounding assumption. A realistic expectation is that some of the mitigating systems will survive and core damage could be prevented. However, even with the bounding assumption, the PRA calculation concludes that the risk associated with work in the pool swell region of the containment for a limited duration is acceptable. The actual duration of work performed in the pool swell region for becemtler 8, 2005 `and December 28, 2005 is 6.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> and 8.25 hours2.893519e-4 days <br />0.00694 hours <br />4.133598e-5 weeks <br />9.5125e-6 months <br /> respectively. This duration did not exceed the acceptable limit established in PSA-009 of 125 hours0.00145 days <br />0.0347 hours <br />2.066799e-4 weeks <br />4.75625e-5 months <br />.

Calculation PSA-009, Revision 3 evaluates the risk associated with work performed in the pool swell region and having the potential for missile generation given a design basis LOCA. These work activities include the building and disassembling of scaffolds in the pool swell region. PSA-009 covers the period from initiation of any work, including the scaffold build to complete removal of any scaffolds.

In a risk informed environment it is acknowledged that events and their consequences have a probability of occurring. The goal of risk informed applications is to limit the probability of events that result in negative consequences to an acceptable level. Using the guidance in NUMARC 93-01, Section 11.3.7.2, metrics that determine an acceptable risk level with established risk management actions are:

Incremental core damage probability (ICDP) less than 1.OE-05.

Incremental large early release probability (ILERP) less than 1.OE-06.

Normal work controls are associated with an ICDP less then 1.0E-6 and a ILERP less then 1.OE-7. The time to achieve an ILERP of 1 E-7 (12.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />) is the limiting duration based on normal work controls. In accordance with NUMARC E3-01 the ICDP and ILERF can be increased to 1 E-5 and 1 E-6, respectively provided non-quantifiables (e.g., weather, etc.) and risk management actions (e.g., declaring protected trains, etc.) are established. Based on those provisions the limiting duration for work in the pool swell region can be increased to 125 hours0.00145 days <br />0.0347 hours <br />2.066799e-4 weeks <br />4.75625e-5 months <br /> over a 12 month period.

For work in the pool swell region of containment, core damage and a large early release will result if a large or intermediat3 LOCA occurs. This implies that the ICDP'and ILERP'are 'quival1nt and thiat-theacceptable 'riskis limited to an ICDP and ILERP of less than 1.0E-06. Based on these guidelines, PSA-009 concludes that the risk associated with work in the pool swell region of the containment, when limited in duration and governed ty risk manageme it actions, is acceptable. The actual duration of work in the pool swell region did not exceeded the acceptable limits.

Based upon the above information, this event is considered to be of very low safety significance.

CORRECTIVE ACTIONS

An Operations Standing Order was issued that did not allow scaffolding to be built in the pool swell region unt I procedure changes were completed.

Changes to PAP-0204 'Housekeeping/Cleanliness Control Program" were implemented to clarify that temporary alterations in support of maintenance cannot adversely affect USAR credited design functions unless an assessment on Technical Specification operability has been performed.U.S. NUCLEAR REGULATORY COMMISSION (1-2001)

LICENSEE EVENT REPORT (LER)

1. FACILITY NAME

2. DOCKET

6. LER NUMBER

3. FAGE SEQUENTIAL REVISION Perry Nuclear Power Plant 05000440 YEAR NUMBER NUMBER 2006 002 000

17. NARRATI /E (if more space is required, use additional copies of NRC Form 366A) o Requirements for performing an evaluation of hydrodynamic loads for building scaffold within the pool swell region were included.

Changes to GCI-0016 'Scaffolding Erection, Modification or Dismantling Guidelines" were implemented to clarify that temporary alterations in support of maintenance cannot adversely affect USAR crec ited design functions unless an assessment on Technical Specification operability has been performed.

o Requirements for performing an evaluation of hydrodynamic loads for building scaffold within the pool swell region were included.

PREVIOUS SIMILAR EVENTS

On November 23, 1987 plant personnel identified that scaffolding had been erected in the containment pool swell region without evaluating the potential hydrodynamic missile hazards. Corrective actions included changes to procedures to require a Mechanical Foreign Item (MFI) evaluation for scaffold to be built in the pool swell region.

Revision 0 of GCI-0016 "Scaffolding Erection, Modification or Dismantling Guidelines" contained the following note: "Scaffolds which are needed within the pool/weir swell region during Modes 1, 2, or 3 will require a 10CFR50.59 review and a Mechanical Foreign Item (M.F.I.) tag before installation per PAP-1402, "Temporary Modification Control". The pool/weir swell region is that area inside the Containment Wetwell below Elevation 623' 4" or in the Drywell between the Drywell wall and the Weir wall below Elevation 613' 0"". This note was replaced in a later revision with a Precaution and Limitation that stated "Scaffolds installed in Containment during Modes 1, 2, or 3 may be considered a Temporary Modification. Ensure requirements of PAP-1402 are satisfied prior to installation." The current revision of GCI-0016 (revision 6) has a Precaution and Limitation that states "Scaffolds shall not be installed in the Containment during Plant Modes 1, 2, or 3 unless Engineering authorizes the scaffold with a RFA CR." Precise guidance with respect to scaffold builds in the pool swell region was replaced over time with less prescriptive information.

PAP-1402, 'Temporary Modification Control", provided detailed guidance on requirements associated wit:1 scaffold builds in the pool swell region. Revision 13 of PAP-1402 (effective 8118/04) deleted reference to pool swell scaffcld requirements as these requirements were now located in PAP-0204, "Housekeeping/Cleanliness Control Program".

A 10CFR5C0.59 rule revision became effective in 2001. The new rule treated scaffolding as a Temporary Alteration in support of a maintenance activity. Because of this new philosophy, guidance for pool swell scaffold activities was removed from PAP-1402, 'Temporary Modification Control". Guidance on responsibilities associated with Temporary Alterations was added to revision i i of PAP-0204. This revision reqiuired only that a risk based assessment of Temporary Alterations in support of maintenance be performed in accordance with PAP-1 924, "Risk-informed Safety Assessment and Risk Management". The revision did not include the requirement to perform a Technical Specification operability evaluation in accordance with 10CFR50.65, "RequiremEnts for Monitoring the Effectiveness of Maintenance at Nuclear Power Plants". These procedure revisions removed the administrative barrier that prevented scaffolding from being built in the pool swell region during Mode 1 and created an unanalyzed condition if a design basis loss of coolant event were to occur.

No similar previous events were identified that had been reported via a Licensee Event Report. Over the past three years, two occurrences of scaffolding being installed in the containment pool swell region were identified at Perry. The se are the December, 2005 instances addressed by this LER.