IR 05000416/1993021

Insp Rept 50-416/93-21 on 931129-1203.No Violations Noted. Major Areas Inspected:Design & Testing of Mod.Insp Reviewed Licensee Implementation of Rwl Indication Ref Leg Backfill Mod

ML20059B572
Person / Time
Site:	Grand Gulf
Issue date:	12/23/1993
From:	Steven Rudisail, Shymlock M NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
To:
Shared Package
ML20059B540	List: IR 05000416/1993021 ML20059B535
References
50-416-93-21, NUDOCS 9401040188
Download: ML20059B572 (6)

Text

UNITED STATES

'/g nech NUCLEAR REGULATORY COMMISSION

[. .~t

%

REGION 11 101 MARIETTA STREET, N.W., sVITE I'900

.

ATLANTA, GEORGIA 303234193 9,

%q o~g s

- ....+

Report No.: 50-416/93-21 Licensee: Entergy Operations, In Jackson, MS 39205 Docket No.: 50-416 License No.: NPF-29 Facility Name: Grand Gulf Inspection Conducted: November 29 through December 3, 1993 Inspector: . 1L/2//</3

~ Rudisail Date Signed Approved by:~ ) N frideb # 25 '/3 Date Signed M.ShymlockMChief Plant Systems Section Engineering Branch Division of Reactor Safety SUMMARY Scope: ,

This routine, announced inspection was conducted in the area of design and testing of modifications. This inspection reviewed the licensee l implementation of a Reactor Water Level Indication Reference leg Backfill  ;

Modification. This system was installed to provide corrective action required '

l by NRC Bulletin 93-03, Resolution of the Issues Related to Reactor Vessel Water Level Instrumentation in BWR Results:

In the areas inspected, violations or deviations were not identified. The implementation of the Reactor Water Level Indication Reference Leg Backfill I Modification was well planned with appropriate levels of engineering and technical support for the desio,n and implementation of this modification. The scope of testing was adequate to ensure system operation as designed. Minor testing problems occurred t.ut the problems were satisfactorily resolved and- ,

subsequent testing acceptable. Appropriate installation and design l instructions, codes and standards were used in the developnaent and l

~

implementation of this modificatio j l

.

9401040188 931228 PDR ADOCK 05000416 G PDR;

'

f

_ _

. . . . _ . -. _ __

'

.

'

REPORT DETAILS j

' Person Contacted Licensee Employees  ;

• D. Berryhill, Engineering Supervisor

• L. Daughtery, Plant Licensing Superintendent

• J. Dianmette, Manager,- Performance & Systems Engineering

• C. Dugger, Manager, Operations

• E. Harris, Technical Coordinator Systems Engineering  !

• C. Hayes, Director Quality  :

• R. Hutchinson, Vice President  ;

• A. Khanifar, Manager Engineering

_ T. Matson, Systems Engineering .

• D. Pace, General Manager ,

R. Patterson, Engineering Supervisor

• R. Ruffin, Licensing Specialist j

• S. Saunders, Systems Engineering Superintendent

• Vining, Manager, Plant Modifications & Construction Other licensee employee contacted during this inspection included craftsmen, engineers, technicians, and administrative personnel, a

Other NRC Employees: i

• R. Bernhard, Senior Resident Inspector  ;

C. Hughey, Resident inspector  ;

.M. Sykes, Intern, Resident Inspector i

• Attended exit interview i Background l On May 28, 1993, the Nuclear Regulatory Commission (NRC) issued Bulletin ~

93-03, Resolution of Issues Related to Reactor Vessel Water Level J Instrumentation.in Boiling Water Reactors (BWRs). .This bulletin ~ :

discussed new information concerning level indication errors that may 1 occur during plant depressurization. NRC Bulletin'(NRCB) 93-0 !

requested certain actions by BWR licensees and required that the licensees notify the NRC of the actions associated with this bulleti ,

Grand Gulf issued their response, to the bulletin on July 30, 1993 for.- !

Grand Gulf Unit 1. The licensee's response stated that the short term '

corrective actions required by NRCB 93-03 had been implemented. The response also stated that the licensee had initiated a project to ,

'

develop and implement a hardware modification to the reactor vesse ' level' instrumentation system to provide the.long term functional reliability required by NRCB 93-03. Also',-in the response'to NRCB 93-03 t the licensee stated'their intent to install a modification that would provide enhanced water level indication' in the core zone rang !

,

!

- ~ . . .- . . - .

'

.

'

2 s Reactor Water Level Leg Continuous Backfill Modification

'

The inspector reviewed the hardware implementation and associated design package. At the conclusion of this inspection the '

installation and testing of the reference leg backfill system was essentially complet The remaining testing was to be completed as the ,

plant came back on-line and increased power level. The licensee was '

monitoring the water level indication to ensure no adverse affects from the backfill flow were introduced into the -level indication. After the plant had increased to 95 percent power, the remainder of the system was placed on-line. For additional information on this portion of the >

modification testing see NRC Inspection Report 50-416/93-2 There are four reference legs in the Reactor Water Level Indication [

system at Grand Gulf. The reference leg backfill system at Grand Gulf used the Control Rod Drive (CRD) Charging System as it's source of water. The system was connected to the CRD charging header through a root valve. Downstream of the root valve was a flowmeter. This was the Brook Model 1452 high pressure indicating flowmete It is a variable glass tube flow rate indicating device using a float in a tapered glass tube. Downstream of the flowmeter were two check valves preceding the i flow restricting orific Grand Gulf utilized the flow restricting orifice to maintain a constant flow rate of approximately 2 to 6 pounds '!

mass per hour. Grand Gulf considered this method of regulating flow .

'

advantageous to regulating flow with a flow regulating valve. The purge flow system has an isolation valve for isolation from the reference legs. Additional valves were installed for venting and draining the syste Overall, the design of the system resulted in a simple layout and configuratio The selection of components such as the use of the flow restricting orifice were pruden Calculations which were required to ,

support the design of the system were reviewed. All calculations i necessary to support the design and installation of the modification had .'

been completed. The inspector reviewed several of the calculation Calculations MC-QlB21-93016, Orifice Sizing Calculation' and Q1B121- <

D101A/D, CRD Charging Water to Reactor Vessel Water Reference leg were reviewed. This calculation supported the selection of the orifice to .

ensure that the specified flow rates would be attainable. The inspector '

also reviewed Calculation CC-QlB21-93018, Qualification of Tubing / Valve Racks for RVLIS Purge Line The calculations appeared correct and ;

supportive of the conclusions reache ,

The inspector also reviewed GENE-637-019-0893, Revision 0, Analysis Guidelines for Backfill Modification of RPV Water Level Instrumentatio '

These guidelines were prepared for the BWR Owners' Group by General Electric (GE). These guidelines were prepared to assist the utilities l in performing analyses to support the Reactor Pressure Vessel (RPV) ;

Water Level Instrumentation System Backfill Modification. This document '

established a procedure for evaluating the effects of-thermal stresses

I

. . . . - _ .

. . . . . ._ _ _ _-

.,

e i

i. -

!

<

3 [

'

on the reference leg condensing pots. The inspector reviewed the scope of the analyses performed by the licenste for this modification. The analyses were consistent with the guidelines and GE recommendation ;

In addition to the installation of the backfill system, Grand Gulf performed a modification to improve the reliability of reactor vessel water level instrumentation. This modification consisted of omitting'

'

the use of the condensing pot reference leg for the fuel zone monitoring instrumentation and expanding the range of the fuel zone instrumentation i by 100 inche The omission of the condensing pot reference leg _ :

connection was replaced by connecting the reference leg side of the l transmitter to the variable leg of the narrow range transmitter. This connection is at a point high enough on the vessel to be above the level '

needed for the expanded range for the fuel zone instrumentation. This

.

modification enhances the reliability of the fuel zone level instrumentation by precluding the effects of non-condensible gasses which were forming in the reference legs with condensing pot The inspector considered these additional measures pruden This gave l the licensee fuel zone instrumentation an expanded range that was not susceptible to the problems from the condensing pot reference leg Also this provided an additional measure of reliable instrumentation i should the backfill purge flow system become inoperabl !

!

4. Testing .

The inspector reviewed the scope of testing that was used to ensure that the installation met the design requirements of the system and that the operation of the system met the design objective Prior to pre-operational testing, the licensee conducted construction '

tests and inspections were performed. Piping and pipe support  ;

installations were inspected to ensure they met the applicable design requirement Visual examinations of piping welds, piping supports :

and piping hangers were performed in accordance with the licensee requirement '

Pressure testing of the system was not required. A visual examination I for leaks was required after the system had been placed in normal operating conditions. _ Hydrostatic testing was required for the piping that was installed at the tie in point of the CRD system to the root !

valve downstream. Inservice leak testing was also performe The inspector reviewed the scope of the testing and the results and considered the testing adequate to demonstrate.that the system had been ;

installed properly and was verified to be ready for pre-operational >

testin l

!

!

. . _ .

.

'

L

-

!

p 4 i

'

Prior to placing the reference leg backfill purge system in service .

preoperational testing was performed. The scope of testing consisted of verification of adequate reactor water vessel reference leg purge performance and verification that the purge function did not adversely !

affect operation of the reactor vessel water level instrumentatio i To accomplish these objectives testing was performed in various modes'of ;

operation as the plant was brought back on-line after a refueling outag During Mode 4, testing was performed to fill and vent the system. Back flow testing of the check valves was performed and a forward flow test ,

of the flow restricting orifice was performed. After fill and vent was completed and the check valves and orifice were tested, the reference leg purge was placed in service. After establishing a flow through the reference leg, various operations were conducted to measure their effect ,

on the reactor vessel water level indication with the purge flow established. CRD pumps were rotated, started and stopped, and control rods were notched in and ou ,

!

The inspector reviewed the results of this phase of testing. During the backflow test of the check valves, the initial test failed because the valves failed to seat. The valves were replaced and the subsequent reverse flow test of these valves was acceptable. When opening the CR0 root valve a water hammer occurred causing the flowmeters to malfunction. The flowmeters were repaired and reinstalled._ The flowmeters have been determined to be extremely susceptible to water hammer. Subsequent to this determination, the licensee used extreme ;

care when opening the CRD root valves. Other minor testing problems such as a leak at the orifice and initial inability to establish acceptable flow were encountered during this phase of testing. These-problems were resolved and the testing satisfactorily complete ;

Disturbances in the Reactor Water Level Instrumentation were noted whe l the purge flow was initially placed in service. The disturbances ranged from 3 inches on the narrow range to 16 inches on the wide rang The ;

licensee attributed the differences in the range of disturbances between

'

the various reference leg to the rate at which the purge flow isolation q valve was operate .

In Mode 2, the reference leg purge flow was -initiated during heat-up. A 1 high speed transient recorder was used to monitor any effects _the purge _ !

flow could produce in the reactor pressure vessel level instruments- i during the ascension to power. Safety relief valves were also cy'cled j during this phase of the testing and the effect of this operation  :

monitored for possible effects on the reactor water level -

instrumentation. This phase of the testing demonstrated that the system operated well during heat-up and perturbations on the system were negligibl I

,,

n

e i ,, u . - , - -. . - , - . ,

,

'

,

. s

.

.;

,

5 .i i System Operation j

,

The inspector reviewed the procedures that were developed to operate the j reference leg backfill system. Operation round sheets were also ,

reviewed. The inspector considered that the procedures and round sheets t were appropriate for the proper operation and monitoring of the syste l

.

The inspector noted that the periodic calibration of the flowmeter had I not been resolved. However, the licensee is evaluating.and determining  !

the frequency and type of periodic check the flowmeter will require to

~

.

accurate indication of purge flo ! Safety Evaluations )

i The inspector reviewed the safety evaluations which were preformed for i the modification on' the reactor water level instrumentation system. The i evaluation were thorough and addressed the applicable concerns. The .i conclusions reached were supporte ;

. Exit Meeting j i

The inspection scope and findings were summarized on November 5, 1993, i'

with those persons. indicated in Appendix A. The inspector described

'

those areas inspected and discussed in detail the inspection result ;

Dissenting comments were not received from the license Proprietary -l information is not contained in this repor l

Acronyms and Abbreviations j l

BWR Boiling Water Reactor i CRD Control Rod Drive 1 GE General Electric .l NRC Nuclear Regulatory Commission  !

NRCB Nuclear' Regulatory Commission Bulletin l RPV Reactor Pressure Vessel ]

RVLIS Reactor Vessel Level Indication System ,

4

i

, ..

, . , . . . - _ _.. .. _

_ . _ _ . . . _ .