05000293/LER-1916-010-01, Re MSIV Inoperability
| ML17174A674 | |
| Person / Time | |
|---|---|
| Site: | Pilgrim |
| Issue date: | 06/14/2017 |
| From: | Perkins E Entergy Nuclear Operations |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 2.17.045 LER 16-010-01 | |
| Download: ML17174A674 (7) | |
| Event date: | |
|---|---|
| Report date: | |
| 2931916010R01 - NRC Website | |
text
~Entergx June 14, 2017 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001
SUBJECT:
Licensee Event Report, 2016-010-01, MSIV lnoperability Pilgrim Nuclear Power Station Docket No. 50-293 Renewed License No. DPR-35 LETTER NUMBER: 2.17.045
Dear Sir or Madam:
Entergy Nuclear Operations, Inc.
Pilgrim Nuclear Power Station 600 Rocky Hill Road Plymouth, MA 02360 The enclosed Licensee Event Report (LER) 2016-010-01, MSIV lnoperability, is submitted in accordance with Title 10 Code of Federal Regulations 50. 73. Revisions to the previously submitted LER will be annotated by a vertical bar to the right of the wording changes.
If you have any questions or require additional information, please contact me at (508) 830-8323.
There are no regulatory commitments contained in this letter.
Sincerely, Evc~in::J~ ~
Manager, Regulatory Assurance EPP/sc
Attachment:
Licensee Event Report 2016-010-01, MSIV lnoperability (4 pages)
Entergy Nuclear Operations, Inc.
Pilgrim Nuclear Power Station cc:
Mr. Daniel H. Dorman Regional Administrator, Region I U.S. Nuclear Regulatory Commission 2100 Renaissance Blvd., Suite 100 King of Prussia, PA 19406-2713 Mr. John Lamb, Senior Project Manager Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Mail Stop 0-8C2A Washington, DC 20555 NRC Senior Resident Inspector Pilgrim Nuclear Power Station Letter No. 2.17.045 Page 2 of2
Attachment Letter Number 2.17.045 Licensee Event Report 2016-010-01 MSIV lnoperability (4 Pages)
NRCFORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 0113112017 (02-2014)
, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
- 6. LERNUMBER
- 3. PAGE YEAR I
SEQUENTIAL I REVISION NUMBER NUMBER 2016
- - 010
- - 01 2 OF4 tThe function of the Main Steam Isolation Valves (MS IVs) is to prevent reactor coolant inventory loss in the event of a steam line break outside primary containment. Also, MS IVs provide a primary containment boundary after a loss of coolant accident inside primary containment. The MS IVs are 20-inch air/spring operated, balanced "Y"-type globe valves. There are four main steam lines. Each steam line has two MSIVs; one inside primary containment and one outside of primary containment. The MSIV outboard valves are located inside the steam tunnel in secondary containment.
tThe MS IVs are part of the primary containment isolation system (PCIS) which provides timely protection against
~he gross release of radioactive materials from the fuel, nuclear system process barrier, and from the primary containment. The PCIS automatically initiates whenever monitored variables exceed preselected operational limits. Immediate shutdown of the reactor is appropriate in such a situation. The scram initiated by the MSIV closure anticipates a reactor vessel low water level scram. The main steam line isolation scram setting is selected
~o give the earliest positive indication of isolation valve closure.
EVENT DESCRIPTION
On December 15, 2016, at 1500 [EST], with the reactor at approximately 22 percent power, while performing a steam tunnel walkdown the MS IVs 2C (A0-203-2C) and 2D (A0-203-2D) were discovered to have steam leaks.
MSIV 2D, had a valve body to bonnet steam leak, and MSIV 2C had a valve packing leak.
~fter the body to bonnet seal weld on MSIV 2D, a post-maintenance test of the valve was completed to check for valve stem leakage. The testing method pressurized main steam pipeline 'D' between the respective inboard and outboard MS IVs. A leak rate test cart was used to pressurize the pipeline with air to perform a soap bubble leak check of the flange. The plant operator who used the leak rate test cart for this purpose related that the total boundary leakage between MSIV 2D and MSIV 1 D was sufficiently low such hat the leak rate test cart's limited air delivery rate easily pressurized the pipe line between the inboard and outboard MS IVs (demonstrating no evidence of gross seat leakage through MSIV 1 D). Therefore, it was reasonable (and within the PNPS licensing basis) to assume the leakage rate through MSIV 1 D was consistent with its RFO 20 as-left Local Leak Rate Test (LLRT) leakage rate for purpose of determining the past operability of penetration X-7D (i.e., Appendix J minimum path leakage limit for penetration X-7D was met).
After the packing on MSIV 2C was partially replaced, a post-maintenance test of the valve was completed to check for valve stem leakage. The testing method pressurized main steam pipeline 'C' between the respective inboard and outboard MS IVs. A leak rate test cart was use8 to pressurize the pipeline with air to perform a soap bubble leak check of the flange. The plant operator who used the leak rate test cart for this purpose related that the total boundary leakage between MSIV 2C and MSIV 1 C was sufficiently low such
~hat the leak rate test cart's limited air delivery rate easily pressurized the pipe line between the inboard and outboard MSIVs (demonstrating no evidence of gross seat leakage through MSIV 1 C). ~herefore, it was reasonable (and within the PNPS licensing basis) to assume the leakage rate through MSIV 1 C was consistent with its RFO 20 as-left LLRT leakage rate for purpose of determining the past operability of penetration X-7C (i.e., Appendix J minimum path leakage limit for penetration X-7C was met). U.S. NUCLEAR REGULATORY COMMISSION (02-2014)
- 1. FACILITY NAME LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET
- 2. DOCKET
- 6. LERNUMBER Pilgrim Nuclear Power Station 05000293 YEAR I
SEQUENTIAL I REVISION NUMBER NUMBER 2016
- - 010
- - 01
- 3. PAGE 3 OF4 On April 15, 2017, during Refueling Outage 21 (RFO 21 ), both the inboard MSIV 1 D and the inboard MSIV 1 C
&ailed their respective LLRT. This was discussed in LER 2017-005-00, 10 CFR 50, Appendix J, Option B, Leak Rate Criteria Exceeded.
SAFETY CONSEQUENCES
There were no consequences to the safety of the public, nuclear safety, industrial safety or ~adiological safety due o this event. Main Steam Line D was isolated on December 15, 2016, in accordance with Technical Specifications (TS) requirements. The MSIV 2D valve body to bonnet flange leak would have created a pathway for release of radioactive material from primary containment. However, the steam leakage from the body to bonnet flange of the outboard MSIV 2D would not have left the secondary containment barrier and would have been processed by standby gas treatment system.
Main Steam Line C was isolated on December 17, 2016, also in accordance with TS requirements. In addition, on December 17, 2016 the plant was shut down and the two outboard MSIVs were repaired and returned to service.
The MSIV 2C valve packing leak with the MSIV 1C valve seat leakage would have compromised the MSIV capability to limit the release of radioactive material from primary containment. However, the steam leakage from the packing leak of the outboard MSIV 2C would not have left secondary containment barrier and would have been processed by standby gas treatment system.
No actions to reduce the frequency or consequence are necessary.
CAUSE OF THE EVENT
The cause of the MSIV 2D leakage in December 2016 was that the gasket used in the valve body to bonnet I
interface was out of specification; resulting in excessive valve body to bonnet gap.
rThe cause of the RFO 21 MSIV 1 D exceeding its leak rate test criteria limits was because the internal guide rib I wear had caused seat damage to the valve.
The cause of the MSIV 2C valve packing leakage in December 2016 was worn packing from scoring on the valve j
stem. The valve stem was polished to remove obtrusions for a smoother finish.
The cause of the RFO 21 MSIV 1 C exceeding its leak rate test criteria limits was because of pilot poppet wear at he stem connection.
In addition, a possible contributing cause during RFO 21 was that the MSIV's were closed at a different time than
- hey normally would have been during most RFOs. Because of extenuating plant conditions the MSIV's were kept open approximately an additional 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. This created a situation where the MSIV's were not closed using steam pressure to close the disk into the seat. Instead the valves were in a cold condition when closed. Normally
~he valves would have been in a hot condition which could obtain better seating.
CORRECTIVE ACTIONS
rThe immediate corrective action to reduce the probability of similar events occurring in the future, in December, 2016, was to seal weld the MSIV 2D valve body to bonnet flange to prevent future leaks. The MSIV 12D then had Post Work Tested (PWT) performed, and the valve was returned to service. (02*2014)
- 1. FACILITYNAME LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET
- 2. DOCKCT" U.S. NUCLEAR REGULATORY COMMISSION
- 6. L.ER NUMBER
- 3. PAGE YEAR I
SEQUENTIAL I REVISION NUMBER NUMBER Pilgrim Nuclear Power Station 05000293 4 OF4 2016
- - 010
- - 01 rThe corrective action to reduce the probability of similar events occurring in the future, for the inboard MSIV 1 D, during RFO 21, was to disassemble and repair the valve body, replace internal parts and perform PWT and return
~he valve to service.
rrhe immediate corrective action to reduce the probability of similar events occurring in the future, in December, 2016, was to partially replace the outboard MSIV 2C valve packing and polish the valve stem.
rThe corrective action to reduce the probability of similar events occurring in the future, for the outboard MSIV 12C, during RF021, wa~ to replace the valve stem, inspect the valve, make needed repairs, replace the packing, perform PWT on the valve and return it to service.
lrhe immediate corrective action to reduce the probability of similar events occurring in the future, for the inboard MSIV 1 C during RFO 21 was to rebuild the valve, perform PWT on the valve and return it to service.
REPORT ABILITY Pilgrim Nuclear Power Station is making this submittal to provide the NRC with additional information regarding he condition of the plant's MSIV's.
/
PREVIOUS EVENTS A review of Pilgrim Nuclear Power Station Licensee Event Reports for the past five years only identified LER 2016-010-00, MSIV lnoperability Led To Condition 'Prohibited By The Plants TS, which was the predecessor. to this supplemental submittal.
REFERENCES:
CR-PN P-2016-1 0039 CR-PN P-2016-10040 CR-PNP-2017-03531 CR-PNP-2017-03588 CR-PNP-2017-05075