05000336/LER-1997-011-02, :on 970402,improperly Adjusted Dual Function Valves Occurred.Caused by Insufficient Program to Ensure, Facility Procedures Clearly Addressed All Related Design Basis Functions.Affected Valves Will Be Adjusted

:on 970402,improperly Adjusted Dual Function Valves Occurred.Caused by Insufficient Program to Ensure, Facility Procedures Clearly Addressed All Related Design Basis Functions.Affected Valves Will Be Adjusted

ML20138J699
Person / Time
Site:	Millstone
Issue date:	05/02/1997
From:	Joshi R NORTHEAST NUCLEAR ENERGY CO.
To:
Shared Package
ML20138J688	List: 05000336/LER-1997-011, Forwards LER 97-011-00,documenting Event Occurred at Unit 2 on 970402.Commitments Made within Ltr Listed 05000336/LER-1997-011-02, :on 970402,improperly Adjusted Dual Function Valves Occurred.Caused by Insufficient Program to Ensure, Facility Procedures Clearly Addressed All Related Design Basis Functions.Affected Valves Will Be Adjusted
References
LER-97-011-02, LER-97-11-2, NUDOCS 9705080299
Download: ML20138J699 (4)

LER-1997-011, on 970402,improperly Adjusted Dual Function Valves Occurred.Caused by Insufficient Program to Ensure, Facility Procedures Clearly Addressed All Related Design Basis Functions.Affected Valves Will Be Adjusted

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(viii) 10 CFR 50.73(a)(2)(ii) 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability
3361997011R02 - NRC Website

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N,RC FORM 366 U.s. NUCLEAR REGULATORY COMMisslord APPROUED B7 OMB NO. 3160-0104 (4-95)

EXPtRES 04/30/S'D

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0 FCCluTY NAME 41)

DOCKET NUMBER (2)

PAGE (3)

Millstone Nuclear Power Station Unit 2 05000336 1OF4 TITLE 44)

Improperly Adjusted Dual Function Valves EVENT DATE (5)

LER NUMBER (6)

REPORT DATE (7)

OTHER FACILITIES INv0LVED (8) sEQUg AL RE $ N MONTH DAY YEAR YEAR MONTH DAY YEAR U

U R

04 02 97 97

- 011 --

00 05 02 97 OPERATING THIS REPORT IS ' UBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR 5: (Check one or more) (11)

MODE (9)

N 20.2201(b) 20.2203(a)(2)(v)

So.73(a)(2)(i) 50.73(a)(2)(viii)

POWER 20.2203(a)(1) 20.2203(a)(3)(i)

X 50.73(a)(2)(ii) 50.73(a)(2)(x)

LEVEL (10) 000 20.2203(a)(2)(i) 20.2203(aH3)(ii) 50.73(a)(2)(iii) 73.71 20.2203(a)(2)(ii) 20.2203(a)(4)

So.73(al(2)(iv)

OTHER

^

20.2203(a)(2)(iv)

So.36(c)(2)

X So.73(a)(2)(vii)

IPf NRC Form 366A LICENSEE CONTACT FOR THIS LER (12)

NAME TELEPHONE NUMBER (include Area Codel R. G. Joshi, MP2 Nuclear Licensing (860) 440-2080 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

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CAUSE

SYSTEM COMPONENT MANUFACTURER

CAUSE

SYSTEM COMPONENT MANUFACTURER ONPRDS PRD l

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SUPPLEMENTAL REPORT EXPECTED (14)

EXPECTED MONN DAY YEAR YES SUBMISslON (If yes, complete EXPECTED sVBMisslON DATE).

X NO DATE (15)

ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines) (16)

On April 2,1997 a report was made to the Nuclear Regulatory Commission (NRC) which documented an event where the closing force for multiple dual function valves [ISV) had been improperly set, resulting in the valves being incapable of closing to a leaktight condition against normal operating systern pressure (NOSP). Eleven of the 23 valves tested were not capable of providing an adequate closing force. This deficiency could result in the potential for a release of radioactive materials to the Auxiliary Building greater than analyzed in the facility Final Safety Analysis Report (FSAR).

The cause of this event was an insufficient program to ensure that facility procedures clearly addressed all related design basis functions.

i T o correct these deficiencies, the affected valves will be adjusted to ensure they property close against containment design pressure and NOSP, and the appropriate procedures shall be revised to ensure that proper valve control parameters are specified and verified after any maintenance activities are performed that could affect dual function valve closing forces.

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PDR ADOCK 05000336 S

PDR MRC FORM 366 (4-95) a v

.U.s. NUCLEAR REGULATORY Commission

1. 4-h5)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME (1)

DOCKET LER NUMBER ' 6)

PAGE (3)

SEQUENTIAL REVislON YEAR NUMBER NUMBER 2OF4 Millstone Nuclear Power Station Unit 2 05000336 97

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00 TEXT W more space is required, use additional copies of NRC Form 366A) (17) 1.

Description of Event

On April 2,1997 a report was made to the Nuclear Regulatory Commission (NRC) which documented an event where the closing force for multiple dual function valves (ISV] had been improperly set, resulting in the valves being incapable of closing to a leaktight condition against normal operating system pressure (NOSP). Eleven of the 23 valves tested were not capable of providing an adequate closing force. This deficiency could result in the potential for a release of radioactive materials to the Auxiliary Building greater than analyzed in the facility Final Safety Analysis Report (FSAR). At the time of discovery of this event, the unit was defueled.

The closing force for these valves was incorrectly set during maintenance activities which occurred between October 1986 and March 1996. These deficiencies were identified as a result of an inspection of the unit's dual function valves which was completed on March 14,1997. The as-found testing was performed as part of a follow-up action to establish controls over the set-up and retesting of valves that must isolate against two different pressure requirements - Containment Design Pressure and NOSP. Testing was initiated because records documenting setpoints for valve closing force against NOSP were not available, in each case, system pressure is greater than primary containment [NH] design pressure. Analysis of the test results revealed that 11 of the 23 valves tested did not have adequate closing force to close tightly or remain closed against NOSP, resulting in a potential failure to isolate upon receipt of a signal to close. Initial Appendix J, Type C Leakage Rate testing indicated that all of these dual function valves were adequately adjusted to isolate against primary containment design pressure.

This condition affected 11 valves in three systems. The affected system, associated containment penetration and valve function are as follows:

Chemical Volume & Control System (CVCS) [CB] - Penetration number 2 (Letdown), Penetration number 3 (Charging), and Penetration number 43 (Reactor Coolant Pump [P] Controlled Bleedoff);

Reactor Coolant Sample Systern - Penetration number 21 (Reactor Coolant System sampling); and e

Liquid Radwaste System [WD]- Penetration number 35 (primary drain tank pump discharge).

e If a failure had occurred in the downstream piping of the letdown line in the Auxiliary Building and if all three of the letdown dual function valves had failed to close tightly against NOSP, a release of radioactive materials outside containment greater than assumed in the FSAR could have occurred, resulting in a higher than assumed offsite radiation dose. Therefore, this event / condition is being reported in accordance with the requirements of 10 CFR 50.73(a)(2)(ii)(a), operating the plant in an unanalyzed condition significantly compromising plant safety.

This condition is also being reported in accordance with the requirements of 10 CFR 50.73(a)(2)(v)(C) and 10 CFR 50.73(a)(2)(v)(D) as a condition that alone could have prevented the fulfillment of a safety function needed to control the release of radioactive material or to mitigate the consequences of an accident.

The remaining eight valves in the Reactor Coolant Sample System, Liquid Radwaste System, and the CVCS (Charging and Reactor Coolant Pump Controlled Bleedoff) isolate lines which are significantly smaller and do not challenge the FSAR assumptions for radioactive releases outside containment. Therefore, these valves are not reportable under 50.73(a)(2)(ii) or 50.73(a)(2)(v).

The three letdown dual functions valves were benchset at varying intervals between August 1993 and March 1996. The benchset values prior to these adjustments are not known. Therefore, the point in time at which all three valves were set below their calculated closing force is unknown. However, at the time of the March 1997 test it was discovered that all three valves were set below their calculated closing force. Therefore, the CVCS RRC FORM 366A (4-95)

NFjC FORM 366A U.S. NUCLEAR REGULATORY COMMisslOM (4-95) 1 LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME (1)

DOCKET LER NUMBER 16)

PAGE (3)

SEQUENTIAL REVislON YEAR NUMBER NUMBER 3OF4 Millstone Nuclear Power Station Unit 2 05000336 97 - 011 -

00 TEXT (11more space is required. use additional copies of NRC Form 366A) t17) dusi function valves for Facility 1 and Facility 2 could not be relied upon to perform their isolation safety function.

This condition is being reported in accordance with the requirements of 10 CFR 50.73(a)(2)(vii)(C) and 10 CFR 50.73(a)(2)(vii)(D) as a common cause that resulted in independent trains or channels becoming inoperable in systems designed to control the release of radioactive material or to mitigate the consequences of an accident.

For the two liquid radwaste dual function valves, which isolate the pump discharge from the primary drain tank, it is believed that both valves have always been adjusted to a closing force below the force required to close I

against NOSP. Therefore, the liquid radwaste dual function valves for Facility 1 and Facility 2 probably would not have performed their isolation safety function. This condition is being reported in accordance with the requirements of 10 CFR 50.73(a)(2)(vii)(C) and 10 CFR 50.73(a)(2)(vii)(D) as a common cause that resulted in independent trains or channels becoming inoperable in systems designed to control the release of radioactive material or to mitigate the consequences of an accident.

i

11. Cause of Event

The cause of this event was an insufficient program to ensure that facility procedures clearly addressed all related design basis functions.

Ill. Analysis of Event The term " dual function valve" refers to a valve that has two separate pressure isolation functions. The first i

function requires the valve to close against containment pressure if a containment isolation signal is received.

The second function requires the valve to isolate against NOSP if operational problems occur. For the 11 dual function valves discussed herein, each valve is part of a system that has a NOSP greater than containment design pressure. Therefore, the valves would isolate properly against containment pressure, but may not isolate properly against NOSP.

Of the 11 deficient valves, eight valves located in the CVCS and Reactor Coolant Sample System isolate lines which are small enough that their failure to isolate would not significantly affect existing assumptions on radioactive releases. However, if a line break occurred outside containment the three letdown valves may have failed to isolate, resulting in a release of radioactive material outside containment beyond the amount postulated in the FSAR. Therefore, this event is considered to be potentially safety significant.

IV. Corrective Action

As a result of this event, the following actions have been, or will be, performed.

1.

Appropriate procedures shall be revised prior to entry into Mode 4 from the current outage to ensure that proper valve control parameters (benchset, air regulator, and stroke length) are specified and verified after any maintenance activities are performed that could affect dual function valve closing forces.

2. The affected valves will be adjusted to ensure they properly close against containment design pressure and NOSP, arid they will be tested to ensure Appendix J, Type C leakage rate testing criteria are met.

These activities will be performed prior to entry into Mode 4 from the current outage.

3.

In the response to NOV 50-336/93-20-06 (NNECO Commitment No. B14747, March 14,1994), Millstone Unit No. 2 committed to specifying retest requirements verifying isolation against full system pressure, as well as containment design pressure for all valves which function in a dual role. This activity is complete.,

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,NRc FOQM 366A U.S. NUCLEAR REGULATORY COMMisslON (4-9 51 LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME (1)

DOCKET LER NUMBER I 6)

PAGE (3)

SEQUENTIAL REVislON EAR NUMBER NUMBER 4OF4 Millstone Nuclear Power Station Unit 2 05000336 97

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00 TEXT (11more space is required, use additional copies of NRC Form 366A) (17)

Current programmatic controls are sufficient to ensure appropriate and adequate procedural reviews. Therefore, corrective action to address identified programmatic deficiencies are not required.

V.

Additional Information

i f

Similar Events

Similar events involving improperly set dual function valves include:

i LER 93-023: On August 30,1993, an engineering analysis conc!Ucied that leakage had occurred earlier that year j

past the seats of two letdown isolation valves. Seat leakage of approximately 2 to 40 gallons per minute was caused by insufficient preload on the actuator spring, which was n e to a lack of detail in the valve overhaul procedure. The spring preloads for the two valves was propert t justed and a plant maintenance procedure was developed which detailed spring bench setting and retest requirements for this type of valve actuator.

Energy Industry identification System (Ells) codes are identified in the text as [XX].

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