05000382/LER-2010-001, For Waterford 3 Steam Electric Station, Regarding Spent Fuel Pool Cooling Single Failure

For Waterford 3 Steam Electric Station, Regarding Spent Fuel Pool Cooling Single Failure

ML100560031
Person / Time
Site:	Waterford
Issue date:	02/23/2010
From:	Murillo R Entergy Nuclear South
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
W3F1-2010-0013 LER 10-001-00
Download: ML100560031 (9)

LER-2010-001, For Waterford 3 Steam Electric Station, Regarding Spent Fuel Pool Cooling Single Failure

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(viii)(B) 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 10 CFR 50.73(a)(2)(ii)
3822010001R00 - NRC Website

text

Entergy Nuclear South Entergy Operations, Inc.

17265 River Road Killona, LA 70057-3093 Tel 504 739 6715 Fax 504 739 6698 rmurill@entergy.com Robert J. Murillo Licensing Manager Waterford 3 W3Fl-2010-0013 February 23, 2010 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001

Subject:

Licensee Event Report 2010-001-00 Waterford Steam Electric Station, Unit 3 (Waterford 3)

- Docket No. 50-382 License No. NPF-38

Dear Sir or Madam:

Entergy is hereby submitting Licensee Event Report (LER) 2010-001-00 for Waterford Steam Electric Station Unit 3. This report provides the details associated with an unrecognized single failure vulnerability associated with the Spent Fuel Pool (SFP) level switch which supplies the low level trip function for both the SFP cooling pumps and the SFP purification pump.

This report contains no new commitments. Please contact Robert J. Murillo at (504) 739-6715 if you have questions regarding this information:

Sincerely, RJM/WJS Attachment: Licensee Event Report 2010-001-00

W3F1-2010-0013 Page 2 cc:

Mr. Elmo E. Collins, Jr.

Regional Administrator U. S. Nuclear Regulatory Commission Region IV 612 E. Lamar Blvd., Suite 400 Arlington, TX 76011-4125 NRC Senior Resident Inspector Waterford Steam Electric Station Unit 3 P.O. Box 822 Killona, LA 70066-0751 U. S. Nuclear Regulatory Commission Attn: Mr. N. Kalyanam Mail Stop O-07D1 Washington, DC 20555-0001 Wise, Carter, Child & Caraway ATTN: J. Smith P.O. Box 651 Jackson, MS 39205 Winston & Strawn ATTN: N.S. Reynolds 1700 K Street, NW Washington, DC 20006-3817 Morgan, Lewis & Bockius LLP ATTN: T.C. Poindexter 1111 Pennsylvania Avenue, NW Washington, DC 20004 R.K. West, lerevents@inpo.org - INPO Records Center

Attachment W3F1-2010-0013 Licensee Event Report 2010-001-00

NRC FORM 366 U.S. NUCLEAR REGULATORY APPROVED BY OMB NO. 3150-0104 EXPIRES 8/31/2010 COMMISSION (9-2007)

Estimated burden per response to comply with this mandatory information collection request:

80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />. Reported lessons learned are incorporated into the licensing process and fed back to industry. Send comments regarding burden estimate to the Records Management Branch EVENT REPORT (LER)

(T-6 E6), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by intemet e-LICENSEE mail to bjsl@nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, NEOB-10202 (3158-0104), Office of Management and Budget, Washington, DC 20503. If a means used-to impose information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the (See reverse for reqruired number of information collection.

digits/characters for each block) informationcollection.

3. PAGE Waterford 3 Steam Electric Station 05000382 1 OF 6

4. TITLE Spent Fuel Pool Cooling Single Failure

5. EVENT DATE

6. LER NUMBER

7. REPORT DATE

8. OTHER FACILITIES INVOLVED FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR iSEQUENTIALuME REVo MONTH DAY YEAR N

50 NUMBER NO HNDA Y

AR N

T_

FIITY NAME DOCKET NUMBER 1

13 2010 2010 - 001 - 00 2

23 2010 NA NA

9. OPERATING MODE

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

El 20.2201(b)

El 20.2203(a)(3)(i)

• [ 50.73(a)(2)(i)(C) 0 50.73(a)(2)(vii)

[E 20.2201(d)

El 20.2203(a)(3)(ii)

[I 50.73(a)(2)(ii)(A) 0l 50.73(a)(2)(viii)(A)

El 20.2203(a)(1)

El 20.2203(a)(4)

. Z 50.73(a)(2)(ii)(B)

[1 50.73(a)(2)(viii)(B)

El 20.2203(a)(2)(i)

El 50.36(c)(1)(i)(A)

El 50.73(a)(2)(iii)

El 50.73(a)(2)(ix)(A)

10. POWER LEVEL El 20.2203(a)(2)(ii)

Ej 50.36(c)(1)(ii)(A)

E] 50.73(a)(2)(iv)(A)

El 50.73(a)(2)(x)

E] 20.2203(a)(2)(iii)

[] 50.36(c)(2)

El 50.73(a)(2)(v)(A)

El 73.71(a)(4) 100 El 20.2203(a)(2)(iv)

El 50.46(a)(3)(ii)

El 50.73(a)(2)(v)(B)

El 73.71(a)(5)

El 20.2203(a)(2)(v)

[I 50.73(a)(2)(i)(A)

El 50.73(a)(2)(v)(C)

El OTHER Specify in Abstract below or in

__ 20.2203(a)(2)(vi)

El 50.73(a)(2)(i)(B)

[3 50.73(a)(2)(v)(D)

REPORTABLE OCCURRENCE This condition meets two reporting criteria:

10CFR50.73(a)(2)(ii) and 1 OCFR50.73(a)(2)(vii)

On January 13, 2010 as a result of continued evaluation of the unrecognized single failure vulnerability associated with FS ILS2000 A2 (FUEL POOL WATER LOW LEVEL SWITCH) [LS], it was determined that this condition is reportable under 10CFR50.73(a)(2)(ii) (Degraded or Unanalyzed Condition) and 10CFR50.73(a)(2)(vii) (Common Cause Inoperability of Independent Trains or Channels) due to one failure being able to disable the safety function of both SFP cooling pumps [DA]. The Updated Final Safety Analysis Report (UFSAR) and General Design Criteria (GDC) require the SFP cooling pumps to meet single failure independence. No actual FS ILS2000 A2 failure occurred, this condition was identified during work preparation.

INITIAL CONDITIONS This condition was identified during a work planning review. No failure of FS ILS2000 A2 occurred.

This was a previously unrecognized single failure that could result in the loss of multiple SFP cooling pumps.

EVENT DESCRIPTION

Spent Fuel Pool Level Switch FS ILS2000 A2 supplies the low level trip function for both the Spent Fuel Pool (SFP) cooling pumps "A" and "B" and the SFP purification pump. Failure of the level switch or loss of power to the level switch will cause all three pumps to trip with no restart capabilities.

This condition is reportable under 10CFR50.73(a)(2)(ii) as described in NUREG-1022 (Event Reporting Guidelines) Section 3.2.4 (Degraded or Unanalyzed Condition).

NUREG-1022 Section 3.2.4 lists a reportable event as an unanalyzed condition that significantly degraded plant safety due to the discovery that a system required to meet the single failure criterion does not do so.

EVENT DESCRIPTION CONTINUED NUREG-0787 (Safety Evaluation Report related to the Operation of Waterford Steam Electric Station Unit No. 3) Section 9.1.3 has the following statement:

The fuel pool pumps can. be powered from redundant divisions of the emergency (Class 1 E) power supplies. Thus, the requirements of GDC 44, "Cooling Water," are met.

10CFR50 Appendix A (General Design Criteria (GDC)) 44 Cooling Water lists the following requirements:

A system to transfer heat from structures, system, and components important to safety, to an ultimate heat sink shall be provided. The system safety function shall be to transfer the combined heat load of these structures, systems, and components under normal operating and accident conditions.

Suitable redundancy in components and features, and suitable interconnections, leak detection, and isolation capabilities shall be provided to assure that for onsite electric power system operation (assuming offsite power is not available)'and for offsite electric power system operation (assuming onsite power is not available) the system safety function can be accomplished, assuming single failure.

UFSAR 9.1.3.1 states the following:

The assumed single failure for a partial core discharge is the failure of a divisional electrical bus which takes out a redundant train of cooling water pumps.

The limiting single failure in calculation ECM98-067'(Limiting Single Failure Thermal Hydraulic Analysis of Waterford 3 Spent Fuel Pool) is the failure of a divisional electrical bus and is non conservative because the newly identified limiting single failure is more adverse.

Based upon the unrecognized single failure identified in the corrective action program condition report (CR-WF3-2009-4908), the requirements of GDC 44 are not met and the UFSAR 9.1.3.1 and ECM98-067 limiting single failures are non conservative. NUREG-1022 reportability criteria is met due to a system required to meet single failure criterion not meeting this requirement.

EVENT DESCRIPTION CONTINUED The FS ILS2000 A2 failure mechanism is also reportable under 10CFR50.73(a)(2)(vii) as described in NUREG-1 022 Section 3.2.8 (Common Cause Inoperability of Independent Trains or Channels).

NUREG-1022 Section 3.2.8 states:

Trains or channels for reportability purposes are defined as those redundant, independent trains or channels designed to provide protection against single failures.

Analysis of events reported under this part of the rule may identify previously unrecognized common-cause (or dependent) failures and system interactions. Such failures can be simultaneous failures that occur because of a single initiating cause (i.e., the-single cause or mechanism serves as a common input to the failures); or the failures can be sequential (i.e.,

cascading failures), such as the case where a single component failure results in the failure of one or more additional components.

The 10CFR50.73(a)(2)(ii) discussion above provides the same details on why this condition meets the reportability criteria under 1 OCFR50.73(a)(2)(vii).

CAUSAL FACTORS This was a latent issue that was present in the spent fuel pool cooling design. UFSAR Section 9.1.3.2.4.3(a) states that the fuel pool water level is monitored by a level switch. This switch actuates a high and a low alarm locally and in the main control room to warn the operator of a system malfunction and trips the pumps. This information has existed since the initial FSAR.

NRC F ORM 366A (9-2007)

CORRECTIVE ACTIONS

This condition and associated corrective actions have been entered and are being tracked in the Waterford 3 Corrective Action Program (CAP).

A temporary modification to jumper the FS ILS2000 A2 level switch was created such that the switch may be easily bypassed by operators if necessary to restore fuel pool cooling.

Operations procedure OP-901-513 (Spent Fuel Pool Cooling Malfunction) will be updated to include contingency steps to recover pumps by alternate means by using the temporary jumper to override the erroneous low level condition.

The temporary modification to jumper the FS ILS2000 A2 level switch will be evaluated to determine if it should be made a permanent modification and associated actions will be taken.

The engineering calculation ECM98-067 (Limiting Single Failure Thermal Hydraulic Analysis of Waterford 3 Spent Fuel Pool) and the UFSAR will be updated.

SAFETY SIGNIFICANCE

UFSAR 9.1.3.3 states the following:

Although it is unlikely that all cooling could be lost to the spent fuel storage pool, it would take approximately2.89 hours0.00103 days <br />0.0247 hours <br />1.471561e-4 weeks <br />3.38645e-5 months <br /> for the bulk pool temperature to rise from 152 0F to 212 0F. This is based on a full core offload discharged starting three days after reactor shutdown. The corresponding heat load is 51.5 x 1 0E6 Btu/hr. This time period allows sufficient time for the operators to intervene and line up an alternate source of replenishing the pool inventory and removing the decay heat.

The temporary modification provides a preplanned method to jumper FS ILS2000 A2 level switchý which would ensure the UFSAR previously stated operator action to restore spent fuel pool cooling could be met.

The failure of the level switch from loss of power is extremely unlikely as it is powered from a static uninterruptable power supply.

9M2007)

SAFETY SIGNIFICANCE CONTINUED Prior to the temporary modification being completed, the FS ILS2000 A2 failure mechanism would not have prevented -operations from replenishing and ensuring the spent fuel remained covered.

Spent fuel pool cooling would have still been capable of being restored but the duration may have been longer than the limiting (full core offload) time of 2.89 hours0.00103 days <br />0.0247 hours <br />1.471561e-4 weeks <br />3.38645e-5 months <br /> but should have still been within the near term. The loss of both SFP cooling pumps caused by the failure of this level switch would generate an immediate alarm in the main control room and an additional control room alarm would be generated as fuel pool temperature increased. With the control room alarms, operations would enter their off normal procedure and take the actions needed to restore SFP cooling. Technicians are continually staffed and would have been available to assist in troubleshooting and installing jumpers around the SFP level switch.

If boiling were.to occur in the SFP, SFP makeup would still ensure that spent fuel remained covered which would ensure the fuel clad temperatures remained within the design limits.. Boiling temperatures are slightly above the SFP component design temperatures (refer to UFSAR Table 9.1-3) but for a short term transient is judged to still be able to perform their intended function once the SFP cooling pumps are returned to service. The other primary concern is associated with potential dose consequences due to boiling. With the spent fuel remaining covered and spent fuel pool cooling being restored in the near term, the potential event consequences are judged.to remain bounded by the fuel handling accident (UFSAR Section 15.7.3.4). This condition is considered to have a low safety significance.

SIMILAR EVENTS

None

ADDITIONAL INFORMATION

Energy industry identification system (EIIS) codes are identified in the text within brackets [].

9-2007)