Information Notice 1990-78, Previously Unidentified Release Path from Boiling Water Reactor Control Rod Hydraulic Units

Previously Unidentified Release Path from Boiling Water Reactor Control Rod Hydraulic Units

ML031130145
Person / Time
Site:	Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, Mcguire, Nine Mile Point, Palisades, Palo Verde, Perry, Indian Point, Fermi, Kewaunee, Catawba, Harris, Wolf Creek, Saint Lucie, Point Beach, Oyster Creek, Watts Bar, Hope Creek, Grand Gulf, Cooper, Sequoyah, Byron, Pilgrim, Arkansas Nuclear, Three Mile Island, Braidwood, Susquehanna, Summer, Prairie Island, Columbia, Seabrook, Brunswick, Surry, Limerick, North Anna, Turkey Point, River Bend, Vermont Yankee, Crystal River, Haddam Neck, Ginna, Diablo Canyon, Callaway, Vogtle, Waterford, Duane Arnold, Farley, Robinson, Clinton, South Texas, San Onofre, Cook, Comanche Peak, Yankee Rowe, Maine Yankee, Quad Cities, Humboldt Bay, La Crosse, Big Rock Point, Rancho Seco, Zion, Midland, Bellefonte, Fort Calhoun, FitzPatrick, McGuire, LaSalle, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant
Issue date:	12/18/1990
From:	Rossi C E Office of Nuclear Reactor Regulation
To:
References
IN-90-078, NUDOCS 9012120148
Download: ML031130145 (11)

UNITED STATES NUCLEAR REGULATORY

COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 December 18, 1990 NRC INFORMATION

NOTICE NO. 90-78: PREVIOUSLY

UNIDENTIFIED

RELEASE PATH FROM BOILING WATER REACTOR CONTROL ROD HYDRAULIC UNITS

Addressees

All holders of operating

licenses or construction

permits for boiling water reactors (BWRs).

Purpose

This information

notice is intended to alert addressees

to potential

problems pertaining

to a previously

unidentified

release path from the control rod drive hydraulic

systems in boiling water reactors that may lead to design basis accident radiation

doses significantly

exceeding

the values specified

in the Final Safety Analysis Report. It is expected that recipients

will review the information

for applicability

to their facilities

and consider actions, as appropriate, to avoid similar problems.

However, suggestions

contained

in this information

notice do not constitute

NRC requirements;

therefore, no specific action or written response is required.Description

of Circumstances:

In June 1989, a design review for unmonitored

release paths at Washington

Nuclear Power Plant Unit 2 resulted in the discovery

of a previously

unidenti-fied radiation

release path in the control rod drive hydraulic

system. This path is postulated

to result from the following

sequence of conditions.

The two control rod drive pumps are shut down following

a design basis accident.There is a break outside of the reactor building (secondary

containment)

in the non-seismically

qualified

piping or tankage to which the control rod hydraulic

system is connected (see Figure 1). Reactor coolant leaks past the double seals in any of the 185 control rod drives and the valves in their associated

hydraulic

control units. The leakage flows back through one or more of the four headers connecting

each of the 185 hydraulic

control units to the common control rod drive (CRD) pump header. The leakage then flows through the CRD pump header and the control rod drive pumps to the break or the conden-sate storage tank located outside of the reactor building.Much of the pathway to the condensate

storage tank lies outside of the reactor building and includes piping that is not seismically

qualified.

In addition, this piping passes close to the air intakes for the control room ventilation

system. Consequently, a failure of the supply piping for the drive pumps s3 -1D8W- /'C

IN 90-78 December 18, 1990 during an accident would not only greatly increase the potential

external release, but could increase the radiation

dose to the control room operators.

General Electric-Nuclear

Energy performed

calculations

for the newly postulated

release path for a design basis accident with concurrent

failure of the non-seismically

qualified

supply piping for the control rod drive system at Washington

Nuclear Power Plant Unit 2. The calculations

incorporated

the source terms specified

in Regulatory

Guide 1.3 and assumed that 10% of the iodine would escape as a gas from the liquid release. These calculations

produced a 30-day thyroid dose for control room operators

of 121 rem per gpm of leakage, a 30-day thyroid dose at the outer boundary of the low-population

zone of 86 rem per gpm of leakage, and a 2-hour thyroid dose at the exclusion

zone boundary of 36 rem per gpm of leakage. A generic communication

discussing

this concern was sent by General Electric-Nuclear

Energy to each BWR utility in July 1989.Discussion:

For the control rod hydraulic

systems at General Electric boiling water reac-tors, the inboard isolation

for the primary containment

is provided by the double seals in the control rod drives, and the outboard isolation

for the primary containment

is provided by valves within the hydraulic

control units.However, past leak tests of the rod drive seals that were performed

by General Electric produced a maximum of 5 gpm per drive. Leakage from the hydraulic control units can also be significant.

As shown in Figure 1, four paths lead from each of the 185 hydraulic

control units to the common CRD pump header. Three of these paths, the accumulator

charging header, the drive header and the cooling header include check valves to prevent the return of water from the hydraulic

units. In addition, water escaping through the accumulator

charging header must leak through the insert side scram valve, and water escaping through the drive header must leak through one of the directional

control valves. However, the check valve in the exhaust header is oriented so as to permit the flow of water back to the CRD pump header.The exhaust water then flows via the CRD pump header back to the reactor vessel (or, as at Washington

Nuclear Power Plant Unit 2, to the reactor water cleanup system) along with the excess pump flow. Therefore, only one normally closed valve prevents water that is leaking out of each of the 185 control rod drives from returning

through the associated

exhaust header to the CRD pump header.During startup testing at Limerick Unit 1, and at Susquehanna

Unit 1, the total leakage from all of the hydraulic

control units combined was measured at 5 gpm and 11 gpm, respectively.

Both of these reactors include additional

check valves at the discharge

of the control'rod

drive pump (area A in Figure 1). A partial audit by the NRC staff indicates

that many of the newer BWR plants have check valves installed

in the discharge

pipe of the control rod drive pumps. However, this audit also showed that other BWR plants, mostly the earlier ones, did not have such check valves. The control rod drive system for BWR/6 plants is de-signed with a testable check valve and a motor-operated

isolation

valve. There-fore, this pathway is applicable

to pre-BWR/6 plants only.

Ie IN 90-78 December 18, 1990 Combining

the General Electric dose calculations

for the postulated

path with the leak rates measured from the hydraulic

units at either Limerick or Susquehanna

produces dose rates significantly

in excess of the values in the Final Safety Analysis Report. Independent

calculations

by the NRC staff pro-duced offsite dose values that were comparable

to the General Electric results.Radiation

release by this path is not possible as long as the control rod drive pumps are kept running. However, continued

operation

of these pumps following an accident cannot be assured, particularly

if the non-seismically

qualified suction piping were to fail.This problem was resolved at Washington

Nuclear Power Plant Unit 2 by the installation

of two check valves in series in the common discharge

pipe from the control rod drive pumps (at area A in Figure 1) to prevent backflow out of the reactor building (secondary

containment).

The Washington

Nuclear Power Plant Unit 2 installation

includes provisions

for leak testing the valves and a leak rate criterion

of 0.01 gpm was established

for these valves.This information

notice requires no specific action or written response.

If you have any questions

about the information

in this notice, please contact one of the technical

contacts listed below or the appropriate

NRR project manager.Division of Operational

Events Assessment

Office of Nuclear Reactor Regulation

Technical

Contacts:

Charles R. Nichols, NRR (301) 492-0854 Donald C. Kirkpatrick, NRR (301) 492-1849 Attachments:

1. Figure 1. BWR Control Rod Drive System 2. List of Recently Issued NRC Information

Notices

Note: At Washington

Nuclear Power Plant, Unit 2, the control rod drive return water Is piped to the reactor w water cleanup system SvITE..t.

.... \SECONDONDARY

OAin4Z( EXHAUST CWHIOL VALV(S CONTAINMENT

~I ~>*PCV "(E S CU OUTSIDE OF DRV BUILDINGA-H

AREA A SCIM VALVIE 6TaLQUT1 COTROL4MmuMRG

RMOO140MIX

ROD To OTHE CONTARNEN

R-OD I.-AJ___ -. CrI DRIVEPUMPSM

~j 0 c Figure 1. BWR CONTROL ROD DRIVE SYSTEM

Attachment

2 IN 90-78 December 18, 1990 LIST OF RECENTLY ISSUED NRC INFORMATION

NOTICES Information

Date of Notice No. Subject Issuance Issued to 90-77 88-23, Supp. 3 90-76 90-75 90-74 90-73 90-72 90-71 90-70 90-38, Supp. 1 Inadvertent

Removal of Fuel Assemblies

from the Reactor Core Potential

for Gas Binding of High-Pressure

Safety Injection Pumps During A Loss-Of-Coolant

Accident Failure Of Turbine Overspeed Trip Mechanism

Because Of Inadequate

Spring Tension Denial Of Access To Current Low-Level

Radioactive

Waste Disposal Facilities

Information

on Precursors

To Severe Accidents Corrosion

Of Valve-To-Torque Tube Keys In Spray Pond Cross Connect Valves Testing of Parallel Disc Gate Valves In Europe Effective

Use of Radi-ation Safety Committees

to Exercise Control Over Medical Use Programs Pump Explosions

Involving Ammonium Nitrate License and Fee Require-ments for Processing

Fin-ancial Assurance

Submittals

for Decommissioning

12/12/90 12/10/90 12/7/90 12/5/90 12/4/90 11/29/90 11/28/90 11/6/90 11/6/90 11/6/90 All holders of OLs or CPs for pressurized- water reactors (PWRS).All holders of OLs or CPs for pressurized- water reactors (PWRs).All holders of OLs or CPs for nuclear power reactors.All Michigan holders of NRC licenses.All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.All NRC licensees authorized

to use by-product material for medical purposes.All uranium fuel fabrication

and conversion

facilities.

All fuel facility and materials

licensees.

OL = Operating

License CP = Construction

Permit

IN 90-78 December 18, 1990 Combining

the General Electric dose calculations

for the postulated

path with the leak rates measured from the hydraulic

units at either Limerick or Susquehanna

produces dose rates significantly

in excess of the values in the Final Safety Analysis Report. Independent

calculations

by the NRC staff pro-duced offsite dose values that were comparable

to the General Electric results.Radiation

release by this path is not possible as long as the control rod drive pumps are kept running. However, continued

operation

of these pumps following an accident cannot be assured, particularly

if the non-seismically

qualified suction piping were to fail.This problem was resolved at Washington

Nuclear Power Plant Unit 2 by the installation

of two check valves in series in the common discharge

pipe from the control rod drive pumps (at area A in Figure 1) to prevent backflow out of the reactor building (secondary

containment).

The Washington

Nuclear Power Plant Unit 2 installation

includes provisions

for leak testing the valves and a leak rate criterion

of 0.01 gpm was established

for these valves.This information

notice requires no specific action or written response.

If you have any questions

about the information

in this notice, please contact one of the technical

contacts listed below or the appropriate

NRR project manager.Origina Signkd IN Charles E Rossi Charles E. Rossi, Director Division of Operational

Events Assessment

Office of Nuclear Reactor Regulation

Technical

Contacts:

Charles R. Nichols, NRR (301) 492-0854 Donald C. Kirkpatrick, NRR (301) 492-1849 Attachments:

1. Figure 1. BWR Control Rod Drive System 2. List of Recently Issued NRC Information

Notices*12/11/90 NJDi *C/OGCB:DOEA:NRR

CHBerlinger

12/L~/jW 111/09/90*OGCB:DOEA:NRR

• SPLB:DST:NRR

• C/SPLB:DST:NRR

• D/U ST:NRR *RPB:ADM DCKirkpatrick

CRNichols

CMcCracken

AThadani TechEd 08/17/90 08/20/90 09/24/90 10/30/90 08/06/90 DOCUMENT NAME: IN 90-78 IN 90-XX August xx, 1990 for these and other plants produced offsite dose values that were comparable

to the General Electric results and that could also significantly

exceed the values specified

in the Final Safety Analysis Report. Radiation

release by this path is not possible as long as the control rod drive pumps are kept running. However, continued

operation

of these pumps following

an accident cannot be ensured, particularly

if the non-seismically

qualified

suction piping were to fall.This problem was resolved at Washington

Nuclear Power Plant Unit 2 by the installation

of two check valves in series in the common discharge

pipe from the control rod drive pumps to prevent back flow out of the secondary

contain-ment. The Washington

Nuclear Power Plant Unit 2 installation

includes provisions

for leak testing the valves. Washington

Nuclear Power Plant Unit 2 planned to establish

a leak rate criterion

for these valves of 0.01 gpm.The control rod drive system for BWR/6 plants is designed with a testable check valve and a motor-operated

isolation

valve, therefore

this pathway is applicable

to only pre-BWR/6 plants.This information

notice requires no specific action or written response.

If you have any questions

about the information

in this notice, please contact the technical

contact listed below or the appropriate

NRR project manager.Charles E. Rossi, Director Division of Operational

Events Assessment

Office of Nuclear Reactor Regulation

Technical

Contacts:

Charles R. Nichols, NRR (301) 492-0856 Donald C. Kirkpatrick, NRR (301) 492-1849 Attachments:

1. Figure of Control Rod Hydraulic

System 2. List of Recently Issued NRC Information

Notices Document Name: UNIDENTIFIED

RELEASE PATH IN*SEE PREVIOUS CONCURRENCES

D/DOEA:NRR

C/OGCB:DOEA:NRR

CERossi CHBerlinger

10/ /90 10/ /90 OGCB:DOEA:NRR

SPLB:DST:NRR

C/SPLB:DST:NRR

D/DST:NRRK4 RPB:ADM DCKirkpatrick*

CRNichols*

CMcCracken*

AThadani TechEd*08/17/90 08/20/90 09/24/90 10M /90 08/06/90

1990 Page 3 f 3 Combining

the General Electric dose calculations

for the postulated

path with the leak rates measured from the hydraulic

units at either Limerick or Susquehanna

produces dose rates significantly

in excess of the values specified in the Final Safety Analysis Report. Independent

calculations

by the NRC staff produced offsite dose values that were comparable

to the General Electric results and that could also significantly

exceed the values specified

in the Final Safety Analysis Report. Radiation

release by this path is not possible as long as the control rod drive pumps are kept running. However, continued operation

of these pumps following

an accident cannot be assured, particularly

if the non-seismically

qualified

suction piping were to fail.This problem was resolved at Washington

Nuclear Power Plant Unit 2 by the installation

of two check valves in series in the common discharge

pipe from the control rod drive pumps (at area A) to prevent backflow out of the reactor building secondary

containment.

The Washington

Nuclear Power Plant Unit 2 installation

includes provisions

for leak testing the valves and a leak rate criterion

of 0.01 gpm was established

for these valves.This information

notice requires you have any questions

about the of the technical

contacts listed no specific action or written response.

If information

in this notice, please contact one below or the appropriate

NRR project manager.Charles E. Rossi, Director Division of Operational

Events Assessment

Office of Nuclear Reactor Regulation

Technical

Contacts: Charles R. Nichols, NRR (301) 492-0854 Donald C. Kirkpatrick, NRR (301) 492-1849 Attachments:

1. Figure 1. BWR Control Rod Drive System 2. List of Recently Issued NRC Information

Notices Document Name: RELEASE PATH NOTICE D/DOEA:NRR

CERossi 11/ /90*D/DST:NRR

AThadani 10/30/90 ok 1vko .*C/OGCB:DOEA:NRR

CHBerlinger

11/09/90*RPB:ADM TechEd 08/06/90*OGCB:DOEA:NRR

DCKirkpatrick

08/17/90*SPLB:DST:NRR

CRNichols 08/20/90*C/SPLB:DST:NRR

CMcCracken

09/24/90

IN 90-XX August xx, 1990 this path is not possible as long as the control rod drive pumps are kept running. However, continued

operation

of these pumps following

an accident cannot be ensured, particularly

if the non-seismically

qualified

suction piping were to fail.This problem was resolved at Washington

Nuclear Power Plant Unit 2 by the installation

of two check valves in series in the common discharge

pipe from the control rod drive pumps to prevent back flow out of the secondary

contain-ment. The Washington

Nuclear Power Plant Unit 2 installation

includes provisions

for leak testing the valves. Washington

Nuclear Power Plant Unit 2 planned to establish

a leak rate criterion

for these valves of 0.01 gpm.This information

notice requires no specific action or written response.

If you have any questions

about the information

in this notice, please contact the technical

contact listed below or the appropriate

NRR project manager.Charles E. Rossi, Director Division of Operational

Events Assessment

Office of Nuclear Reactor Regulation

Technical

Contacts: Charles R. Nichols, NRR (301) 492-0856 Donald C. Kirkpatrick, NRR (301) 492-1849 Attachments:

1. Figure of Control Rod Hydraulic

System 2. List of Recently Issued NRC Information

Notices Document Name: UNIDENTIFIED

RELEASE PATH IN*SEE PREVIOUS CONCURRENCES

OGCB:W EA:NRR DOrirkpathick

08/e 9/90 VC<SPLB:DST:NRR

CRNichols 08AV2/9M;*^

CISPLB:DST:NRR

CMcCracken

OF/p/90 D/DOEA:NRR

CERossi 08/ /90 D/DST:NRR AThadani 408/ /90 V1 C/OGCB:DOEA:NRR

CHBerlinger

08/ /90*RPB:ADM TechEd 08/06/90

IN 90-XX August xx, 1990 The Washington

Nuclear power installation

includes provisions

for leak testing the valves. Washington

Nuclear Power has established

a very low leak rate criterion

for these valves (.01 gpm was indicated).

A partial check by the NRC staff indicates

that many of the newer BWR plants already have check valves installed

in the control rod drive pump discharge

pipe. However, this check also showed that other BWR plants, mainly the earlier ones, did not have such check valves.This information

notice requires no specific action or written response.

If you have any questions

about the information

in this notice, please contact the technical

contact listed below or the appropriate

NRR project manager.Charles E. Rossi, Director Division of Operational

Events Assessment

Office of Nuclear Reactor Regulation

Technical

Contact: Charles R. Nichols, NRR (301) 492-0854 Attachments:

1. Figure of Control Rod Hydraulic

System 2. List of Recently Issued NRC Information

Notices Document Name: UNIDENTIFIED

RELEASE PATH IN D/DOEA:NRR

CERossi 08/ /90 D/DST:NRR AThadani 08/ /90 C/OGCB:DOEA:NRR

CHBerlinger

08/ /90 RPB:ADM TechEd J ai P 08/C /90 OGCB:DOEA:NRR

SPLB:DST:NRR

DCKirkpatyi

.- CRNichols 08/' /9 xF 08/ /go C/SPLB:DST:NRR

CMcCracken

08/ /90