ML060400058

Enclosure 1 - Slides - NRC Briefing HPCI

ML060400058
Person / Time
Site:	Duane Arnold
Issue date:	12/31/2005
From:	Nuclear Management Co
To:	Office of Nuclear Reactor Regulation
spaulding D, NRR/DORL, 415-2928
References
Download: ML060400058 (12)

Text

Duane Arnold. .

Safe - Reliable - Predictable -

-Z77 NRC Briefing

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HPCI Nux Nuclear Eclec/

December 2005

Duane Arnold NRfC Briefing HPCI Operability Determination Interim Corrective Actions & Results vRoot Cause Evaluation

Further Analysis VI 2.K co NMC Nuclear Excellence 2 .

Operability Determination ssues Identified:

• Existence of a steam void at the top of the discharge pipe.

^ Identified non-conformances associated with T-TPflT A ; hgre1k Ad111V~

XX%-/X %.L im-,* a1LLgIe h er Luau design.

• Discharge piping should not have been insulated. (

• September 29 venting done at lower CAT eve

Operability Determination ctions Taken:

- Established Event Response Team

• Around-the-clock Engineering support.

• Obtained additional resources from Monticello and MPR.

- Successfully vented HPCI several times with higher CST level.

- Completed OE review:

• Internal

• External

• Operating Modes 7 -

JMC Ito Nu(I,IearExcellence 4

Operability Determination Actions Taken:

- Evaluated Non-Conformances (insulation and high pipe temperatures).

- Reviewed Transient Recorder data.

- Completed thorough system walkdown.

Note: Operations performs quarterly leakage detection walkdowns.

- Static and dynamic testing performed. (

• Static - with pressure transducer.

• Dynamic - with accelerometer.

- Conducted three NMC challenge-boards(' NM Comtdto Nuclear ExceS 5

Operability Determination Potential Causes of Steam Void Formation:

- Valve leakage.

- Heat conduction from feedwater line.

- Lower CST water level.

NMC Nuclear Excelenc 6

Operability Determination

==

Conclusions:==

- HPCI was capable of performing its safety function.

- Non-conformances do not impact system operability.

Steam volume near MO-23 12 disc does not cause ladetrimental later hammLer.

- Steam volume does not affect HPCI start times.

- Void size collapse similar for both surveillance and injection modes.

- No current or past evidence of water hammqr.

- HPCI declared Operable, but degraded & nod<

conforming on 10/12/05.

NMC to Nuclear Excellence 7 '

Interim Corrective Actions &

Results Interim Compensatory Actions:

1I. HPCI suction lined up to CST with water level of 15 ft or greater, otherwise HPCI keep fill system in service.

i2. Periodic venting of HPCI discharge piping.

- Started at an increased frequency then extended out to TS SR frequency based on results.

- Performed to validate conclusions of OPR.

3. Shiftly monitoring of HPCI discharge piping temperatures.

- Performed to verify void size does not change. // N "IC V m7 td to Nuclear Excellenc

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Interim Actions & Results

-0Results:

-- Discharge pipe temperatures monitored shiftly.

- Acceptance criteria: < 115 'C.

- Results: Upper pipe temp steady @ - 113 'C.

- Table below summarizes venting and temperature monitoring results

ate Oct 14 Oct 17 Oct 21 Oct 26 Nov I Nov 8 Nov 22 Dec 6 ent 24 sec 8 sec 11 sec 28 sec 21 sec 15 sec 6.3 se seQc pe 113 0 C 1130 C 113 0 C 1130 C 113 0 C 1130 C 114 0 C emp _ . __ _ _ _

Results support original conclusions i N CE 3C itted to Nuclear N-L

Root Cause Evaluation Root Causes Ieeffects of "turbulent penetration" were not taken into account in the original HPCI system design.

<- Unknown to the site, thermal energy was being delivered to MO-23 12 via the nhenornenon of turbulent penetration.

Thermal energy is being conducted through MO-2312's valve disc.

- Steam is being produced on the low-pressure sice of the MO-2312 valve disc due to higher than designed temperature existing.

Root Cause Evaluation

'urbulent Penetration:

- Previously un-recognized phenomena.

- Discussed in:

• IAEA-TECDOC- 136 1, Assessment and management of aging of major nuclear power plant components important to safety, dated Juy20

• EPRI MRP-32, Thermal Fatigue Monito ing Guidance, dated April 2001.

NMC Ito Nuclear Excellence I11I

Further Analysis Analysis to be performed:

- Determine bounding void size.

- Determine minimum CST water level to assure

- Determine effects of pipe movement with determined void size and collapse underma.

and automatic start scenarios.

- Complete a past operability determin iŽ Current Schedule.,