ML20081D532

Requests That NRC Review & Approve Inservice Testing Program Relief Requests RSW-1 & NB-1

ML20081D532
Person / Time
Site:	Monticello
Issue date:	03/13/1995
From:	Hill W NORTHERN STATES POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9503200284
Download: ML20081D532 (8)

Text

, 3-l Northem States Power Company l l

414 Nicollet Mall Minneapolis, Minnesota 55401-1927 Telephone (612) 330-5500 March 13,1995 10 CFR Part 50 Section 50.55a US Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 MONTICELLO NUCLEAR GENERATING PLANT Docket No. 50-263 License No. DPR-22 Request for Review and Approval of Inservice Testino Proaram Relief Reauests RSW-1 and NB-1 Enclosed for NRC staff review are relief request RSW-1 and NB-1. Relief Request RSW-1 is a new request for relief from the code requirements for stroke time testing as applied to control valves in the Residual Heat Removal Service Water (RHRSW) system. This revision of Relief Request NB-1 revises the basis for relief from valve exercising testing of the Main Steam Safety / Relief Valves due to a change to the plant technical specifications goveming safety / relief valve surveillance requirements.

NRC Inspection Report 50-263/94008 identified unresolved item 94008-2 concerning testing of control valves in the RHRSW system. Monticello provided our resolution of the unresolved item by letter dated November 28,1994 and in discussions held with members of the NRC Staff on December 9,1994. Relief Request RSW-1 is provided to resolve the above open item as discussed during the December 9.1994 conference call and in NRC letter dated December 23,1994, with Subject " UNRESOLVED ITEMS (NRC INSPECTION REPORT NO.

50-263/94008(DRS)).

Relief Request NB-1 was submitted for NRC review by letter dated December 7,1992 with subject, " Revision 1 to Third Ten-Year Inservice Testing Program". Approval of Relief Request NB-1 was provided by NRC letter dated July 6,1993, with subject "MONTICELLO NUCLEAR GENERATING PLA.NT- APPROVAL OF THIRD TEN-YEAR INSERVICE TESTING PROGRAM *. NRC letter dated September 15,1994, issued Amendment 92 to Facility Operating License No. DPR-22 for the Monticello plant. This amendment revised the requirement which previously required a minimum of seven of eight safety / relief valves to be bench checked or replaced with bench checked valves each refueling outage. The revised requirement specifies that the valves be tested in accordance with Section XI Inservice Testing Requirements of the ASME Boiler and Pressure Vessel Code. ASME Section XI, Subarticle IWV-3200, states that pressure relief devices shall be tested in accordance with the requirements of ANSI /ASME OM-1-1981. Paragraph 1.3.3.1.2 of ANSI /ASME OM 1-1981 addresses the applicable test frequency of Class 1 pressure relief devices, and requires that:

9503200284 950313 PDR P

ADOCK 05000263 PDR

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.a USNRC! ' NORTHERN STATES POWER COMPANY. i March 13,1995 +

Page 2 "All valves of each type and manufacture shall be tested within each subsequent 5 year period with a minimum oi20% of tha valves tested within any 24 months. This 20% . j shall be previously untestec velds, if they exist." l Relief Request NB-1 provides an exception from the quarterly valve exercising tests specified in the ASME Code (Section XI, Subarticle IWV-3410) in recognition of the fact that testing of  !

the subject valves during power operation is impractical. However, the altamative testing of - i the relief request reflects our past practice by stating that all eight safety / relief valves are l bench checked or replaced each outage, which is no longer necessarily the case per the  ;

issued license amendment. The enclosed revision to NB-1 proposes revised altamative  !

testing.  ;

The proposed change will have no significant adverse impact on the reliability of the safety / relief valves. Although any single valve may ultimately have the safety function tested less frequently, we expect overall reliability to increase since the most common performance problems associated with these valves, seat leakage and setpoint drift, can be induced by  ;

valve handling or disassembly work. The proposed change would enable us to minimize such  !

work to the extent permitted by Section XI of the ASME Code and ANSI /ASME OM-1-1981. I These valves will be exercised each operating cycle to test the power operated function.

This letter contains no new NRC commitments, nor does it modify any prior commitments. This submittal does modify Monticello regulatory obligations regarding implementation of the ASME Code per 10 CFR 50.55a. Please contact Mary Engen, Sr Licensing Engineer, at (612) 295 -  !

4 1291 if you require further information.

// h., ' ff W J Hill Plant Manager Monticello Nuclear Generating Plant c: Regional Administrator- 111, NRC NRR Project !.5 nager, NRC Sr Resident inspector, NRC State of Minnesota 1 Attn: Kris Sanda J E Silberg

Enclosure:

Relief Request RSW-1 i Relief Request NB-1 l

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RELIEF REQUEST NUMBER RSW-1 System: Residual Heat Removal Service Water (RHRSW)

Valves: CV-1728 CV-1729 Class: B-1 Category: 3 ,

Function: To open, providing a flow path for RHRSW through the RHR heat exchanger.

Test Requirement from which Relief is Sought:

Section XI, paragraph IWV-3413, (a) The limiting value of Full-stroke time of each power operated valve shall be specified by the Owner. Full-stroke time is that time interval from initiation of the actuating signal to the end of the actuating cycle. ,

(b) The stroke time of all power operated valves shall be measured to the nearest second...whenever such a valve is full-stroke tested.

Section XI, Paragraph IWV-3417, ,

(a) If, for power operated valves, an increase in stroke time of 25% or more from the previous test, ... test frequency shall be increased to once each month until corrective action is taken....

Basis for relief:

10 CFR 50, Section 50.55a(f)(5) & (6) states, (in part):

(5)(iii) If the licensee has determined that conformance with certain code requirements is impractical for its facility, the licensee shall notify the commission....

(6)(i) ... The commission may grant relief and may impose altemative requirements ... giving due consideration to the burden upon the licensee....

In addition,10 CFR Part 50, Section 50.55a(a)(3) states (in part):

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RSW-1 Page 2 of 3 -

" Proposed alternatives to the requirements of paragraphs ... may be used when.. .

(i) The proposed alternatives would provide an acceptable level of quality' and safety...."-

lWV-3413 requires that a limiting value of full stroke time be established for a j power operated valve and that the stroke time be measured whenever such a j valve is full stroke tested. Performing full stroke time testing of these valves is i impractical based on the control scheme design of the valves, adverse plant j impact, and the functional requirements of the valves.

i IWV-3413 states that full stroke time is that time interval from initiation of the I actuating signal to the end of the actuating cycle. The control scheme design of these valves does not receive an actuation signal (neither by manual handswitch '

nor by automatic logic) to stroke to the position required to fulfill their safety function. RHRSW valves CV-1728 and CV-1729 pre air operated control valves on the outlet line of the RHRSW side of the "A" and "B" RHR heat exchangers,  :

respectively. These control valves maintain a differential pressure between the RHRSW process stream and the RHR process stream during RHRSW system ,

operation. The valves are controlled by a positioner, controlled by a differential pressure indicating controller (DPIC). The DPIC senses pressure.on the RHRSW discharge line and the RHR inlet line to the RHR heat exchanger. The-desired differential pressure control point, and thus the desired valve position for -

system flow, is manually set by the operator by manual adjustment of the DPIC .,

setpoint. The valve positioner positions the valve and modulates the valve  ;

position as necessary to maintain this control point. Stroke time testing of these  !

valves on quarterly basis is not consistent with the design of the valve's control scheme and is not in the interest of plant safety. l These valves are interlocked to receive a closed signal when the Residual Heat .l Removal Service Water (RHRSW) pumps are de-energized. This interlock is  ;

provided to ensure that system water inventory is not lost during system ,

shutdown. Stroke time testing of valves CV-1728 and CV-1729 when the Residual Heat Removal Service Water pumps are de-energized would result in the loss of liquid fill for a significant portion of the RHRSW system as well as  :

require the bypassing of an interlock designed to minimize the potential for water hammer. Such testing increases the possibility of an adverse water han.mer  :

during startup of the RHRSW system as well as requires filling and venting of  !

the system following the stroke time testing. In addition to the adverse impact on l plant operation, such testing results in an undesirable burden on plant resources - '

via the expenditure of person-hours and person-rem to perform system filling  !

and venting. l l

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' troke time testing of the valves during RHRSW pump operation negates the S

loss of system fill concern; however, this testing would also have an adverse impact on plant safety and equipment integrity. Stroke time testing during pump operation would require the valve be initially in the closed position during pump l operation. ' Establishing the initial test conditions of a closed valve during pump : '

operation would result in an undesirable deadheading of the pump. Subsequent opening of the valve to perform stroke time testing will result in pump runout if a single RHRSW pump is in operation, an undesirable condition which adversely _ -

impacts pump integrity and performance. The pump runout concern can be n addressed by stroke timing the valve open during operation of both RHRSW pumps; however this exacerbates the pump deadheading concerns and would result in undesirable transients on the system.

Proper stroke time testing would require the plant to modify the control logic of the valves. This hardship is not offset by an increase in public safety, in addition, the application of stroke time testing requirements to control valves has recently become an issue with the OM code committee and is subject to change and/or clarification. The proposed attemative testing is an effective means to ensure the valves perform their safety function and is consistent with other valve  !

category test requirements, such as check valve exercisinc  ;

Alternate Testing:

l IWV-3412 provides for demonstrating the necessary valve disk movement by observing indirect evidence (such as changes in system pressure, flow rate,  :

level, or temperature), which reflect stem or disk position. The most representative test of the capability of valves CV-1728 and CV-1729 to perform .

their intended function is performed during inservice testing of the RHRSW pumps. Quarterly testing of the RHRSW pumps verifies the capability of the valves to operate properly to pass the maximum required accident flow as well  ;

as the recording of the valve position necessary to achieve required flow f conditions. Testing of the valves in this manner demonstrates valve .

performance capability and provides a means to monitor for valve degradation.  !

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I RELIEF REQUEST NB-1 l l

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. System: Nuclear Boiler / Main Steam Va'ves:

I RV-2-71 A, RV-2-718, RV-2-71C, RV-2-71D, RV-2-71E, RV-2-71F, RV-2-71G, RV-2-71H Category: B, C-1 Class: 1 Function: To provide automatic depressurization or overpressure protection for the reactor coolant pressure boundary.

Code Test Requirement: IWV-3410, Valve Exercising Test i

Basis for Relief:

10 CFR 50, Section 50.55a(f)(5) & (6). states, (in part):

(5)(iii) If the licensee has determined that conformance with certain code requirements is impractical for its facility, the licensee shall notify the '

commission....

(6)(i) ... The commission may grant relief and may impose altemative requirements ... giving due consideration to the burden upon the licensee....

In addition,10 CFR Part 50, Section 50.55a(a)(3) states (in part): ,

" Proposed alternatives to the requirements of paragraphs ... may be used when... ,

(i) The proposed attematives would provide an acceptable level of quality and .

safety,..."

These valves have an active, self actuation safety function to open and relieve an overpressurization condition in the reactor vessel. The valves also have an auxiliary actuating device (as defined in OM-1-1981) that acts to open the valves and depressurivs the reactor vessel. This function allows low pressure emergency core cooling systems to inject during a LOCA (ADS) and also controls reactor pressure in

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, NB-1 Page 2 of 2 certain' design transients (Iow low set). The ADS automatic actuation provides for d'epressurizing the rector vessel to permit low pressure ECCS system injection during a loss of coolant accident. The low low set automatic actuation provides control of the opening and closing setpoint following s scram during pressurization transients.

Although ?hese valves have an auxiliary actuating device, they can not be treated and tested as category B, power operated valves. The requirements to stroke time them quarterly is not within the design capability f the valves or the plant. First of all, these valves have a passive safety function to remain closed and provide reactor coolant pressure boundary. Exercising them during power operation would cause a severe reactor power and pressure transient that could result in a reactor scram. It also increases the potential for second stage or pilot stage leakage due to seat wear or fouling. If this leakage is high enough, it can cause a spurious SRV lift and prevent e reclosure of the valve. This condition is equivalent to an unisolable small break LOCA event. The NRC states in several documents that such challenges to the ADS function of the main steam safety / relief valves should be minimized. Therefore, justification to perferm an exercise test on a once-per-cycle frequency is well established.

The reason the valves can not be stroke timed to provide meaningful data is that there is no direct indication of valve position. Their stroke time is less than one second and can only be measured by indirect means such as changes in SRV discharge line pressure and temperature indication. This results in a high degree of variability in the measured stroke times due to other plant variables such as valve pneumatic supply pressure, recctor pressure, turbine bypass valve condition, measuring instrumentation response time, etc. This prohibits repeatable test conditions without a heavy burden on the licensee to fix these parameters during each test to within a narrow enough range commensurate with a less than one second stroke time. This burden is not offset by an increase in public safety.

Alternative Testing:

These valves will be monitored for degradation by testing them in accordance with all applicable sections of OM-1-1981, including the requirement: ft,r auxiliary actuating devices. This testing is in accordance with the Monticello plant technical specifications.

The valves will also be tasted in accordance with Technical Specification 4.6.E which includes disassembly and inspection of at least two SRVs each refueling outage.

All SRVs will be exercised at reduced recctor pressure. M clace, each operating cycle to verify the open and close capability of the valve.

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TRANSMITTAL MANIFEST l NORTHERN STATES POWER COMPANY  :

3 NUCLEAR LICENSING DEPARTMENT MONTICELLO NUCLEAR GENERATING PL ANT  ;

Request for Review and Approval of inservice Testino Proaram Relief Reauests RSW-1_and NB-1 -

Correspondence Date: March 13,1995  ;

Monticello Intemal Site Distribution Special Instructions Kaleen Hilsenhoff......USAR file.. . . ...........Yes No_x_

Steve Ludders ..........NRC Commitment .....Yes No_x_

Lila Imholte.... ...........Monti OC Sec . . . ...Yes No_x_ - 11, No dist to OC members below if YES Mel Opstad.. . . ... .....Monti SAC Sec. .. ....Yes No_x_ - 5 l

Monticello Intemal Site Distribution:

• Monti Document Control File Monti Site L!c File W J Hill, Plant MGR Steve Ray, SR Res insp, NRC ,

Al Wojchouski ,

Steve Hammer '

Dean Carstens D:ve Pennington Jim Freborg NSP Intemal Distribution E L Watzl, VP Nuc Gen R O Anderson, Dir LMI, SAC Mike Wadley, Pl Communicat on Dept Yes No_x_  :

t Extemal NSP Distribution

<dese Centref Desh"40RCA. Kris Sanda, State of Minn Regional Admin-lli,NRC J E Silberg -

Beth Wetzel, NRR-PM, NRC

• Advance Distribution made by Site Licensing Manifest Date: March 14,1995