05000334/LER-2008-001, Control Room Envelope Air Intake During Normal Operation Higher than Assumed in Design Basis Accident Dose Calculations
| ML090130091 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 01/09/2009 |
| From: | Sena P FirstEnergy Nuclear Operating Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| L-08-387 LER 08-001-00 | |
| Download: ML090130091 (6) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(ii) 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 |
| 3342008001R00 - NRC Website | |
text
C,
'9 FENOC FirstEnergy Nuclear Operating Company Beaver Valley Power Station P.O. Box 4 Shippingport, PA 15077 Peter P. Sena III Site Vice President 724-682-5234 Fax: 724-643-8069 January 9, 2009 L-08-387 10 CFR 50.73 ATTN: Document Control Desk U. S. Nuclear Regulatory Commission Washington, DC 20555-0001
SUBJECT:
Beaver Valley Power Station, Unit Nos. 1 and 2 BV-1 Docket No. 50-334, License No. DPR-66 BV-2 Docket No. 50-412, License No. NPF-73 LER 2008-001-00 Enclosed is Licensee Event Report (LER) 2008-001-00, "Control Room Envelope Intake During Normal Operation Higher Than Assumed in Design Basis Accident Dose Calculations." This event is being reported in accordance with 10 CFR 50.73(a)(2)(i)(B).
There are no regulatory commitments contained in this submittal. Any actions discussed in this document that represent intended or planned actions are described for the NRC's information, and are not regulatory commitments.
If there are any questions or if additional information is required, please contact Mr. Colin P. Keller, Manager, Regulatory Compliance at 724-682-4284.
Sincerely, Peter P. Sena III Attachment cc:
Mr. S. J. Collins, NRC Region I Administrator Mr. D. L. Werkheiser, NRC Senior Resident Inspector Ms. N. S. Morgan, NRR Project Manager INPO Records Center (via electronic image)
Mr. L. E. Ryan (BRP/DEP)
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150-0104 EXPIRES 08/31/2010 (9-2007)
, the NRC may digits/characters for each block) not conduct or sponsor, and a person is not required to respond to, the information collection.
- 3. PAGE Beaver Valley Power Station Unit Number 1 05000334i 1 of 5
- 4. TITLE Control Room Envelope Air Intake During Normal Operation Higher Than Assumed In Design Basis Accident Dose Calculations 5.
- 8. OTHER FACILITIES INVOLVED FACILITY NAME MONTH I DAY I YEAR YEAR I
NO, 11 10 2008 2008 -
001 00
- 9. OPERATING MODE 1
- 10. POWER LEVEL 100 %
- 11. THIS REPORT LI 20.2201(b)
[
20.2201(d)
[
20.2203(a)(1)
LI 20.2203(a)(2)(i)
LI 20.2203(a)(2)(ii)
Ej 20.2203(a)(2)(iii)
E] 20.2203(a)(2)(iv)
E] 20.2203(a)(2)(v)
[] 20.2203(a)(2)(Vi)
IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)
[] 20.2203(a)(3)(i)
F] 50.73(a)(2)(i)(C)
LI 50.73(a)(2)(vii)
E] 20.2203(a)(3)(ii)
E] 50.73(a)(2)(ii)(a)
E] 50.73(a)(2)(viii)(A)
E] 20.2203(a)(4)
[] 50.73(a)(2)(ii)(B)
LI 50.73(a)(2)(viii)(B)
E] 50.36(c)(1)(i)(A)
E] 50.73(a)(2)(iii)
LI 50.73(a)(2)(ix)(A)
E] 50.36(c)(1)(ii)(A)
E] 50.73(a)(2)(iv)(A)
LI 50.73(a)(2)(x)
E] 50.36(c)(2)
F] 50.73(a)(2)(v)(A)
F] 73.71(a)(4)
[j 50.46(a)(3)(ii)
LI 50.73(a)(2)(v)(B)
F] 73.71(a)(5)
E] 50.73(a)(2)(i)(A)
[
50.73(a)(2)(v)(C) rI OTHER Specify in Abstract below
[
50.73(a)(2)(i)(B)
[
50.73(a)(2)(v)(D) or in DESCRIPTION OF EVENT (Continued)
The subject CRE tracer gas in-leakage testing also identified that the inleakage during the control room recirculation ventilation mode (outside air is isolated, but CREVS fans have not yet been manually started) was 292 +/- 23.cfm, which could be slightly above the assumed design value of 300 cfm if the full tolerance of +23 cfm is assumed.
The limiting BVPS Unit 1/Unit 2 calculated control room dose which credits CREVS occurs during a DBA Loss of Coolant Accident (LOCA). Although the normal unfiltered intake flow value may only be utilized for a very short time in the limiting LOCA dose calculation (i.e.,
the first 77 seconds - time for full CRE isolation as initiated by a Containment Isolation-Phase B signal), the contribution of normal unfiltered intake flow to the calculated control room operator'post-DBA dose is not insignificant for all DBA dose calculations.
There was no need to credit CREVS actuation for some DBAs described in the Units' UFSARs since assuming continuous normal control room intake for 30 days post-DBA yielded acceptable calculated control room doses. The effect of an excessive normal intake flow rate is more pronounced for those DBAs which do not credit CREVS initiation in their control room design basis dose calculation than for the DBAs which do credit CREVS initiation. For example, the current BVPS Unit 1 Steam Generator Tube Rupture (SGTR)
DBA dose calculated for the control room operator does not credit any CRE isolation or CREVS operation and produced a calculated control room dose which was smaller than the limiting LOCA control room dose which does credit CREVS operation. However, re-calculating control room dose using the recently measured excessive normal operation air intake value would cause the BVPS Unit 1 SGTR DBA control room dose to exceed the value currently listed in the UFSAR for SGTR and also above the current limiting LOCA calculated control room dose. Thus, the excessive normal operation air intake value creates an inadequate CRE boundary since it, by itself, invalidates the bounding control room dose calculation by resulting in a calculated control room dose which exceeds the current BVPS Unit 1 and Unit 2 bounding control room dose. An inadequate CRE boundary represents a condition prohibited by plant Technical Specification 3.7.10 for CREVS.
CAUSE OF EVENT
The cause of this event was less than adequate (LTA) CRE boundary definition stated in site procedures which resulted in the failure to ensure adequate maintenance and surveillance activities on appropriate CRE components.
The three different modes of the control room ventilation operation (i.e., Normal, Recirculation, and Pressurization Modes) and their effect on the CRE boundary (as addressed by Technical Specification 3.7.10) was not described in site procedures. The
CAUSE OF EVENT (Continued) current site procedures are inadequate since they mainly describe only the CRE building structure components. As a result of this LTA CRE boundary definition, the function of the event related dampers to establish a CRE in-leakage boundary in the Normal Mode of operation had not been clearly recognized as a critical aspect of CREVS operability. In the Pressurization Mode of operation (i.e., post-DBA), two upstream series isolation dampers are closed to form the ventilation boundary - not the event related (normal intake throttle) dampers. The common site understanding of the definition of the CRE boundary was typically associated with the Pressurization Mode of operation. Therefore, the need to establish periodic preventative maintenance tasks and/or flow, measurements to maintain normal intake flow rates within limits for the event-related dampers was not recognized until after the dampers degraded to the point that the in-leakage flow rates in the normal mode of operation exceeded the maximum value of 500 cfm.
ANALYSIS OF EVENT
The BVPS Unit 1 intake purge damper (1VS-D-40-1G) was degraded by a hole created by corrosion (which was subsequently determined to have been potentially accelerated by ice-removal material spread for winter walkway clearance). Corrosion is a slow process which does not occur in a short time frame. Hence, this was firm evidence that the abnormally high CRE intake flow, exacerbated by the 1VS-D-40-1G pathway hole, existed prior to the recent tracer gas testing. This flow rate through the closed purge damper would have been in addition to any flow via the normal intake pathways, and would have exceeded the licensing basis analyses limit for the total normal intake flow rate assumed in the dose calculations of record (less than 500 cfm total intake limit). This would have caused a higher-than-bounding CRE dose and hence, an insufficient CRE boundary.
Technical Specification 3.7.10 Action B applies for an inoperable CRE boundary and contains three Required Actions with Completion Times ranging from 'Immediately' to '90 days'. The inadequate CRE boundary' would have been a condition prohibited by plant Technical Specifications for greater than the time frames allowed by Technical Specification Action B completion times. Therefore, this is reportable pursuant to 10 CFR 50.73(a)(2)(i)(B).
The potential higher than design inleakage during the control room recirculation ventilation mode (292 cfm +/- 23 cfm) was not caused by'the 1VS-D-40-1G corrosion hole, and thus, it was not a firm pre-existing condition. Therefore, this was not reportable pursuant to 50.73(a)(2)(i)(B).
An evaluation was performed to assess the impact of the changes in the control room ventilation intake/inleakage flows measured by the tracer tests on the control room N
ANALYSIS OF EVENT (Continued) operator dose following a design basis accident. The evaluation determined that the regulatory limit of 5 REM TEDE would not be exceeded following any DBA. Therefore, no significant impact on the control room operators to perform their duties following postulated design basis accidents are expected, and this event is considered to have very low safety significance.
There was no loss of safety function for the CRE pursuant to 1 OCFR 50.73(a)(2)(v) since the largest increase in calculated control room dose resulting from the measured increase in normal intake air flow would not have exceeded the General Design Criteria 19 regulatory limit of 5 REM TEDE, even though the dose increase would have been more than the bounding value currently listed in the Unit's UFSAR.
CORRECTIVE ACTIONS
- 1. Immediate actions included closing both Units' CREVS isolation dampers to reduce the normal intake of unfiltered air to a value less than assumed in the DBA dose calculations.
- 3. A site document will be developed to clearly define the CRE boundary to also include boundaries used during normal and recirculation modes of control room ventilation modes of operations, and not just the post-CREVS initiation pressurization mode of operation.
- 4. Periodic preventative maintenance and periodic intake flow measurements will be incorporated for the normal CRE intake dampers.
Completion of the above and other corrective actions are being tracked through the BVPS corrective action program.
PREVIOUS SIMILAR EVENTS
A review found no prior BVPS Unit No. 1 or BVPS Unit No. 2 Licensee Event Report within the last three years for an event involving the control room boundary/envelope.
CR 08-49260