ML20029C847
| ML20029C847 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 04/19/1994 |
| From: | Richard Anderson NORTHERN STATES POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| IEB-93-002, IEB-93-2, NUDOCS 9405020061 | |
| Download: ML20029C847 (7) | |
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s Northem States Power Company 414 Nicollet Mall Minneapolis, Minnesota 55401 1927 Telephone (612) 330-5500 April 19, 1994 NRCB 93-02 Supp 1 U S Nuclear Regulatory Commission Attnt Document Control Desk Washington, DC 20555 MONTICELLO NUCLEAR GENERATING PLANT Docket No. 50-263 License No. DPR-22 Initial (60 day) Response to NRC Bulletin 93-02 Supplement 1,
" Debris Pluccina of Emeroency Core Coolina Suction Strainers" The purpose of this letter is to provide our initial (60 day) response to NRC Bulletin 93-02 Supplement 1, dated February 18, 1994.
The bulletin describes staff concerns related to the potential loss of Emergency Core Cooling Systems (ECCS) due to the possibility of suction strainer plugging and lequests that licensees implement certain interim actions until the issue is resolved.
Reporting Requirement No. 1 of the bulletin supplement required chat all action addressees submit, within 60 days of the date of the bulletin supplement, a written report indicating whether or not the addressee intends to comply with the actions requested therein, a description of the planned actions, and the schedule for completing them.
We have completed our review and assessment of the bulletin and will concit to comply with the interim actions contained therein pending final resolution of this issue.
Details concerning specific planned actions and the schedule for those actions are provided as Attachment 2 to this letter.
As suggested in the bulletin, we are working with the BWROG to obtain a final resolution of this issue.
This letter (including Attachment 2) contains the following new NRC commitments:
1.
We will comply with the interim actions requested in NRC Bulletin 93-02 Supplement 1 pending final resolution of this issue.
2.
The EOP contingency procedures will be revised to add a caution statement regarding the use of containment sprays to address the potential for wash down of post-LOCA debrio. This action will be completed by May 19, 1994.
3.
A new procedure is being developed to formally document our normal inopection of the drywell for foreign materials prior to startup.
This 9.O n n 9405020061 940419
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t USNRC NORTHERN STATES POWER COMPANY April 19, 1994 Page 2 procedure will be available for use by May 19, 1994.
4.
Operator training on the new abnormal procedure ("ECCS Suction Control During LOCA") will be completed by May 19, 1994.
Please contact Terry Coss, Sr Licensing Engineer, at (612) 295-1449 Af you require any additional information concerning this submittal.
(
Y Roger O Anderson 3
Director j
Licensing and Management Issues j
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cca Regional Administrator-III, NRC NRR Project Manager, NRC Resident Inspector, NRC State of Minnesota, Attnt Kris Sanda J Silberg Attachment (1):
Affidavit to the US Nuclear Regulatory Commission Attachment (2):
Monticello 60 Day Response to NRCB 93-02 Supplement 1
4 UNITED STATES NUCLEAR REGULATORY COMMISSION NORTHERN STATES POWER COMPANY MONTICELLO NUCLEAD, GENERATING PLANT DOCKET NO. 50-263 Initial (60 day) Response to NRC Bulletin 93-02 Supplement 1,
" Debris Pluccino of Emeroency Core Coolina Suction Strainers" Northern States Power Company, a Minnesota corporation, hereby provides the 60 day response information required by NRC Bulletin 93-02 Supplement 1.
This letter contains no restricted or other defense information.
NORTHER STATES POWER CO ANY k.
By MA
, /ftoger o Anderson Director Licensing and Management Issues Onthis/4 day of
/(f6 before me a notary public in and for said ([ounty, perscdially appeared 'Rclger O Anderson, Director, Licensing and Management Issues, and being first duly sworn acknowledged that he is authorized to execute this document on behalf of Northern States Power Company, that he knows the contents thereof, and that to the best of his knowledge, information, and belief the statements made in it are true an that it is not interposed for delay.
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k~ JUDY L. KLAPPERICK
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f NOTARY PUBUC W:NNESOTA ANOKA COUNTY My Commisskm Expirn sept 29 9p$
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4 Monticello 60 Day Response to NRCB 93-02 Supplement 1 The following is the 60-day Monticello response to NRC Bulletin 93-02, Supplement 1.
Action Recuested
" Provide training and briefings to apprise operators and.other appropriate emergency response personnel of the information contained
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herein and in the referenced information notices regarding the potential
'l for suppression pool strainer clogging."
Monticello Response j
l A shift seminar was held to inform Operations personnel and emergency response personnel of concerns with potential ECCS suction strainer plugging. This training included a requirement to read NRCB 93-02 and Supplement 1, as well as NRC Information Notices 88-28, 90-07, 92-71 and 93-34, to assure personnel were familiarized with industry events related to the suction strainer clogging concern.
Action Reauested
" Assure that the emergency operating procedures (EOPs) make the operator aware of possible indications of ECCS strainer clogging and provide guidance on mitigation."
Monticello Response A combination of existing plant procedures, training, and a new event-based abnormal operating procedure (titled "ECCS Suction Control During LOCA")
satisfies this requested action. The new abnormal operating procedure, used in conjunction with the EOPs, gives the operator clear direction if clogging of the ECCS strainers is thought to have occurred. An abnormal procedure is
- the appropriate means to address strainer clogging because abnormal proce'ures d
are event based rather than symptom based an is the case for the EOPs.
This abnormal procedure has been implemented and Operator training on the new procedure will be completed by May 19, 1994.
Action Reauested 4
" Institute procedures and other measures to provide compensatory action to prevent, delay or mitigate a loss of available NPSH margin under LOCA conditions. Such measures should be consistent with providing the~
design basis emergency' system functions for core'and containment
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April 19, 1994 Page 2 cooling. Actions to assure sufficient core and containment cooling may includet
- Reduction of flow (consistent with delivering the required ECCS flow) through the strainers to reduce head loss and extend the time for debris deposition."
Mgnticello Response Current procedures allow ECCS pumps to be throttled or secured if reactor water level reaches the desired band, and allow the operator to ignore NPSH limits if level is below the top of active fuel (TAF).
The new abnormal operating procedure will instruct operators to throttle the in service ECCS division as needed to meet demand.
These actions will help reduce entrainment of debris and deposition on the auction strainers, thus prolonging the operability of the in service ECCS division.
" Operator realignment of existing systems to allow back flushing of clogged strainers."
Nonticello Responsg A review by Monticello operations and Engineering personnel indicates there is no existing back flushing capability which would be effective following a LOCA.
" Operator realignment of existing systems to allow injection to the core from water sources other than the suppression pool. "
M2nt;1g_e11o Feenonae Presently, the EOPs provide guidance regarding the allowed injection sources into the Reactor Pressure Vessel. Many of the available preferred injection systems have pump suction sources other than the suppression pool (e.g. CRD, condensate /feedwater, j
HPCI, RCIC, and Core Spray).
HPCI, RCIC and Core Spray are capable of taking a suction from either the condensate Storage Tanks (CSTs) or the suppression pool. The normal and preferred suction source for HPCI and RCIC is the CSTs.
The EOPs address overriding automatic suction transfer signals when necessary so
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n April 19, 1994 Page 3 that HPCI and RCIC remain aligned to the CSTs.
The EOPs also allow manually aligning Core Spray suction to the CSTs.
If these preferred injection systems are inadequate or unavailable, alternate injection systems would then be used for vessel level control.
For examples RHR Service Water (via RHR-RHRSW cross tie),
- Fire Water (via Fire Water-RHR cross tie),
- Service Water (to Condenser via SW emergency makeup connection, then to Reactor Vessel via condensate and Feedwater system)
Other possible methods that are not specifically addressed by the EOPs but are addressed by other plant procedures aret Service water to Condenser via SW emergency makeup connection, then Condensate and Feedwatec to CSTs,.then to Reactor Vessel using ECCS pumps,
- Fill CSTs from local fire hose stations, inject into Reactor Vessel using ECCS pumps,
- Fill CSTs using fire pumper truck, inject into reactor Vessel using ECCS pumps.
" Intermittent operation of the containment sprays, when possible, to reduce the transport of debris to the' strainers."
Monticello Response The EOP contingency procedures will be revised to add a caution statement regarding the use of containment sprays to address the potential for wash down of post LOCA debris.
This action will be I
completed by May 19, 1944.
"Other plant-specific measures which' assure availability of sufficient core and containment cooling to meet the design basis
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of the plant."
I Monticello Response Monticello has many normal and alternate methods of core cooling.
These plant-specific methods are' reflected in existing procedures, training,;and the new abnormal operating procedure as discussed above.
The following additional actions have already been taken-
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April 19, 1994 Page 4 or will be taken by the indicated date:
A precaution has been added to the RHR'and Core Spray-Operations Manuals to remind operators of the ECCS suction strainer plugging concern.
The Operations Manual revisions have been issued and this action is complete.
- A new procedure is being developed to formally document our
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normal inspection of the drywell for foreign materials.
The procedure will require the removal of such materials prior to sealing of the drywell and plant start-up.
Review and approval of this procedure is nearly complete and it'will be available for use by May 19, 1994.
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- The procedure that controls and documents the internal inspection of the suppression chamber specifically addresses inspection of the suction strainers, including cleaning if required. The procedure, as written,' adequately addresses the concerns of NRCB 93-02 Supplement 1 and does not require revision.
The primary containment-hatch closure procedure specifically-calls for a cleanliness inspection of the. torus interior prior to closure.
The procedure, as written, adequately addresses the concerne of NRCB 93-02 Supplement 1 and'does not require revision.
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