Information Notice 1988-61, Control Room Habitability - Recent Reviews of Operating Experience
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C.
20555
August 11, 1988
NRC INFORMATION NOTICE NO. 88-61:
CONTROL ROOM HABITABILITY - RECENT REVIEWS
OF OPERATING EXPERIENCE
Addressees
All holders of operating licenses or construction permits for nuclear power
reactors.
Purpose
This information notice is being provided to alert addressees to potential
problems resulting from design or analysis deficiencies identified in control
room ventilation systems.
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
The NRC has received several construction deficiency and licensee event
reports pertaining to safety systems that are used to ensure control room
habitability. These reports identified potential safety concerns resulting
from design deficiencies, which were attributed to inadequate analysis and
an inability to justify those conditions that were assumed in previous evalu- ations of plant design and operation. These reports are summarized below.
Comanche Peak 1 and 2:
On January 15, 1988, the permit holder determined that radiation doses to
control room operators for some postulated radiological accidents could
exceed the limits of General Design Criterion 19 of Appendix A to 10 CFR 50.
This determination was attributed to an inadequate analysis of control room
habitability systems for postulated radiological accidents.
Particular ac- cident scenarios that were incompletely analyzed included a fuel handling
accident and a rupture of a radioactive gaseous waste tank. To correct
this situation, the licensee is developing new calculations, upgrading the
existing control room intake radiation monitors and associated cables to
safety-related Class 1E requirements, and installing two additional safety- related Class 1E radiation monitors, one in each control room intake.
88850248 '
IN 88-61 August 11,
1988 Quad Cities:
on November 25, 1987, the licensee's engineering department discovered that
design basis assumptions used in the control room habitability study were
inconsistent with technical specification requirements.
The study was con- ducted to satisfy a requirement of the NRC's TMI Action Plan.
The adsorption
efficiencies of the standby gas treatment system and control room HYAC system
were assumed at 99 percent for organic iodide removal.
The relevant technical
specifications, however, require only an organic iodide removal efficiency more
than or equal to 90 percent. All the filters meet the technical specification
requirements.
Since December 31, 1984, tests of filter efficiencies indicate
that the relevant assumptions of the study were met with two exceptions. The
licensee attributes the cause for this condition to be an inadequate review of
design and analysis during the development of the study.
Vogtle 1 and 2:
On July 2, 1987, plant engineering personnel identified an inadequacy in the
dose analysis for control room operators. On receipt of a safety injection
signal or a control room outside air intake high radiation signal, the control
room heating, ventilating, and air conditioning (HVAC) system is automatically
transferred from the normal system units to the essential control room (ECR)
fan-filter units in the emergency mode of operation.
The ECR system consists
of two redundant and physically separated 100 percent capacity fan-filter units
for each side of the control room, associated with the corresponding reactor
unit (four for the combined Unit 1 and Unit 2 control room (Figure 1)).
Each
of the ECR units belongs to a different safety train, but portions of the out- side air intake ductwork and control room supply and return ductwork are common
to each of the units.
On initiation of the ECR system, the associated motor- operated dampers for the essential units are automatically opened and those
for the normal units are automatically closed.
When both of the ECR fan-filter units are operating, loss of power to one of
these units can reduce the amount of outside air available to pressurize the
control room.
This can happen because the dampers losing power fail in the
"as-is" position. At the time of the identification of the problem, no back- draft dampers were installed.
This degrades the ECR HVAC system by establishing
flowpaths through the common ductwork and the ductwork of the failed unit back
to the suction of the operating unit, which could potentially reduce the outside
air flow to the control room and reduce the control room pressure below the
design value. Maintenance of the design control room pressure is required to
minimize unfiltered inleakage.
The licensee concluded that the actual effect on control room pressure could
not be calculated in the absence of test data and decided to modify the system
by installing backdraft dampers, as noted on Figure 1, for the ECR HVAC systems
of both Units 1 and 2.
IN 88-61 August 11, 1988 On July 4, 1987, an additional condition was discovered that could have caused
an insufficient control room pressure.
air supply ductwork. The common air supply ductwork has intakes from the out- side atmosphere associated with both Units 1 and 2. Redundant isolation dampers
in series are provided for both Unit 1 and Unit 2 duct openings from the outside
atmosphere. During construction, the Unit 2 duct opening had been isolated by
locking the dampers closed. If one of the outside air isolation dampers for
Unit 1 had closed as the assumed single failure of an active component, no
source of outside air would be available to the control room (shared by both
Units) and the required pressure would not be maintained. Because the licensee
had removed chlorine gas sources from the site, the capability to isolate toxic
gases was no longer needed.
Thus, the licensee deactivated and tagged open the
outside air isolation dampers.
For all these problems, the licensee concluded that the defective conditions
would have been discovered earlier with an adequate failure modes and effects
analysis.
Beaver Valley 2:
On March 27, 1987, the permit holder determined that timers initiated by con- tainment isolation phase B signals were not served with uninterruptible power
as required. These timers are designed to actuate banks of compressed air to
supply the control room emergency pressurization system one hour after receipt
of the isolation signal.
They were powered from the respective fan control
circuit energized by an emergency ac distribution panel fed from an emergency
motor control center. Loss of offsite power would interrupt power to the motor
control center. If a loss of power occurred after timer initiation, the timers
would reset to the beginning of the timing cycle and would not begin the cycle
until power was restored to the emergency motor control center.
The compressed
air would thus not be supplied after one hour.
To enhance the reliability of
the safety systems, the licensee revised the circuitry to power the timers from
the Class lE 125-V dc battery system.
McGuire 1:
On November 5, 1987, the licensee discovered during an 18-month surveillance
test of the control area ventilation and chilled water system that control room
pressure was below the technical specification requirement. The licensee de- termined that the cause was leaking seals on seven control room doors.
The
doors were designed to seal by seating against sealing strips in the door
frames.
Although not visibly deteriorated, the sealing material apparently
had been deformed and compressed over time from normal use of the doors. The
licensee adjusted manual volume dampers to increase total train air flow and
the proportion of outside air flow to the maximum 60 percent allowed in the
I
IN 88-61 August 11,
1988 test procedure.
This action was effective in increasing control room pressure
to meet the technical specification requirement.
The licensee installed sealing
tape around the seven doors and established a preventive maintenance program to
inspect the seals on all control room doors every 6 months for a 1-year period.
The licensee plans to determine an appropriate frequency for preventive mainte- nance of the door seals.
The surveillance test of the control area ventilation
and chilled water system will also be repeated every 6 months until sufficient
information is obtained for determining an appropriate frequency.
Farley 1:
On June 5, 1987, the licensee discovered that none of four fire dampers in the
control room ventilation system would fully close and latch with or without air
flow because they had not been exercised and/or lubricated or, in one case, be- cause a latch was damaged.
In addition, investigation revealed that the dampers
would not have received an actuation signal from a Firestat set to sense 1600F
in the control room ceiling because of installation errors.
The licensee at- tributed the problems to three causes: a design deficiency pertaining to the
full closure and latching of the dampers, inadequate testing of the actuation
circuitry, and inadequate preventive maintenance of the dampers.
Discussion:
In addition to the above, the NRC has recently completed an engineering evalu- ation, "Design and Operating Deficiencies in Control Room Emergency Ventilation
Systems," AEOD/E802, April 1988 based on recent events that highlight single
failure vulnerabilities in control room emergency ventilation systems.* The
NRC also has recently conducted a survey of control room habitability systems
at 12 operating plants.
Numerous discrepancies were found between the analyzed
and actual performance of these systems.
For example, differences exist between
design, construction, operation, and/or testing of these systems and the de- scriptions and analyses provided in licensing documents, as for example in the
assumptions used in the toxic gas and radiation dose calculations.
In addition, analyses assumptions have not always been consistent with technical specifi- cation requirements.
The NRC has issued several information notices related
to this subject (see Attachment '2).
Resolution of Generic Issue 83:
Control
Room Habitability is also ongoing.
- A copy of the report is available in the NRC Public Document Room, 1717 h
Street, N.W., Washington, D.C.
20555, for inspection and copying.
IN 88-61 August 11,
1988 No specific action or written response is required by this information notice.
If you have any questions about this matter, please contact one of the techni- cal contacts listed below or the Regional Administrator of the appropriate
regional office.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contacts: Vern Hodge, NRR
(301) 492-1169
Charles R. Nichols, NRR
(301) 492-0854 Attachments:
1. Figure 1. Schematic Air Flow Path Diagram of Essential Control Room
Heating, Ventilating, and Air Conditioning System (ECP HVAC) at Vogtle.
Assumed Containment Isolation Signal for Unit 1 with Train B Failed.
2. List of Information Notices Related to Control Room Habitability Systems
3. List of Recently Issued NRC Information Notices
I OUTSIDE
L ,
AIR
OUTSIDE;
AIR% v vv
OUTSIDE AIR SUPPLY DUCT
(
(
cn
c
LA CO 0~
FIGURE 1. SCHEMATIC AIR FLOW PATH DIAGRAM OF ESSENTIAL CONTROL ROOM HEATING, VENTILATING, AND AIR > o =
CONDITIONING SYSTEM (ECR HVAC) AT VOGTLE. ASSUMED CONTAINMENT ISOLATION SIGNAL FOR
-C
UNIT 1 WITH TRAIN B FAILED.
0C
03
Attachment 2
IN 88-61 August 11,
1988 LIST OF INFORMATION NOTICES
RELATED TO CONTROL ROOM HABITABILITY SYSTEMS
NO.
86-76
85-89
83-62 TITLE
DATE
Problems Noted in Control Room
Emergency Ventilation Systems
Potential Loss of Solid-State
Instrumentation Following Failure
of Control Room Cooling
Failure of Redundant and Toxic Gas
Detectors Positioned at Control Room
Ventilation Air Intakes
August 28, 1986
November 19, 1985
September 26, 1983
'-
.dachment
3 IN 88-61
August 11. 4988
Page I of I
LIST OF RECENtLY
ISSUED
NRC INFORMIATION
NOTICES
InfTornation
Notice No.
Subject
88-60
Inadeouste Design and
Installation of Watertight
Penetration Seals
B8-04.
Inadecuate Qualifitation
Supplerent I
and Documentation of Fire
Barrier Penetration Seals
88-59
Kain Steam Isolation Valve
Guide Rail Failure at
Waterford Unit 3
88-58
88-57
88-56
88-55 B8-54
88-S-
Potential Probiems with
ASEA Brown Boveri
TE-S1L
Time-COercurrent Pelays
Potential Loss of Safe
Shutccwn Eoulprent Due to
Premature Siliccr Controllee
Rectifier Failure
Potential Prcblems wtth
Siliccre Foam Fire Barrier
Penetration Seals
Potential Problems Caused
by Sirgle Failure of an
Engineered Safety Feature
Swing Bus
Fajiure of Circuit Breaker
Following Installation of
Amptector Direct Trip
Attactrent
Licensee Violations of NRC
Reculations. Whicn Leo to
leoical Diagnostic
misaoministrations
Date of
Issuance
S/11B8
8/9/88
819/88
8/8/E8
8/8/88
8/4/88
8/3/18
7/28/68
7/28es
Issued to
All holders of OLs
or CPs for nuclear
power reactors.
All holders of MLs
or CPs for nuclear
power reactors.
All holders of OLs
or CFs for nuclear
power reactors.
All holders of OLs
or CPs 'or nuclear
power oeactors.
All holders of QLs
or CFs for nuclear
power reactors.
All holders of OLs
or CFs 'or nuclear
power reactors.
All holders of CIs
or CPs for nuclear
power reactors.
All holders of OLs
or CPs for nuclear
power reactors.
All manufacturers and
distributcrs of radio- ptarraceuticals for
huran use. nucledr
pharracies. ano
necical licensees.
-T
- Doeratino License
- Ccnstructicr. Permit
UNITED STATES
NUCLEAR REGULATORY COMMISSION
WASHINGTON, D.C. 20555
OFFICIAL BUSINESS
PENALTY FOR PRIVATE USE. $300
FIRST CLASS MAIL
POSTAGE & FEES PAID
USNAC
P£RMIT Ne.
S67
IN 88-61 August 11,
1988 No specific action or written response is required by this information notice.
If you have any questions about this matter, please contact one of the techni- cal contacts listed below or the Regional Administrator of the appropriate
regional office.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contacts:
Vern Hodge, NRR
(301) 492-1169
Charles R. Nichols, NRR
(301) 492-0854 Attachments:
1. Figure 1. Schematic Air Flow Path Diagram of Essential Control Room
Heating, Ventilating, and Air Conditioning System (ECR HVAC) at Vogtle.
Assumed Containment Isolation Signal for Unit 1 with Train B Failed.
2. List of Information Notices Related to Control Room Habitability Systems
3. List of Recently Issued NRC Information Notices
- SEE PREVIOUS CONCURRENCES
08/G /88 NRR *A C SPLB:DEST:NRR
JWCraig
05/06/88
- C/OGCB:DOEA:NRR
CHBerlinger
05/31/88
- SAD/DEST:NRR
AThadani
05/13/88
- PPMB:ARM
TechEd
04/05/88
- D/DEST:NRR
LCShao
05/16/88
- OGCB:DOEA:NRR
CVHodge
03/31/88
- SPLB:DEST:
CRNichols
03/31/88
IN 88-XX
May xx, 1988 habitability systems at 12 operating plants.
Numerous types of discrepancies
are described involving differences between (1) the design, construction, operation and/or testing of these systems and (2) corresponding technical
specifications when compared with the descriptions and analyses provided in
licensing basis documents, Including assumptions in the toxic gas and radiation
dose calculations.
No specific action or written response is required by this information notice.
If you have any questions about this matter, please contact the technical
contacts listed below or the Regional Administrator of the appropriate regional
office.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contacts:
Vern Hodge, NRR
(301) 492-1169
Charles R. Nichols, NRR
(301) 492-0854 Attachments:
1. Summaries of Recent Reports Concerning Control Room Habitability
2. Figure 1. Schematic Flow Path Diagram of Essential Control Room Heating, Ventilating, and Air Conditioning System at Vogtle 1 and 2
3. List of References
4. List of Recently Issued NRC Information Notices
- SEE PREVIOUS CONCURRENCES
- OGCB:DOEA:NRR
CVHodge
03/31/88
- SPLB:DEST:NRR
CRNichols
03/31/88 D/DOEA:NRR
CERoss i
05/ /88
- A/C/SPLB:DEST:NRR
JWCrai g
05/06/88 C¢6 C/OGCB:DOEA:NRR
CHBerl inger
O/n-/88 SAD/DEST:NyJSp
AThadani Al
0 5 /y 8 8
- PPMB:ARM
TechEd
04/05/88 D/DEST:N/I
LCShao
05//88 A
IN 88-XX
May xx, 1988 control room habitability systems at 12 operating plants. Numerous types of
discrepancies are described between the design, construction, operation and
testing of these systems and corresponding technical specifications compared
with the descriptions and analyses provided in licensing basis documents, including assumptions in the toxic gas and radiation dose calculations. The
NRC plans to distribute the report to all holders of operating licenses or
construction permits for nuclear power reactors.
No specific action or written response is required by this information notice.
If you have any questions about this matter, please contact the technical
contacts listed below or the Regional Administrator of the appropriate regional
office.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contacts:
Vern Hodge, NRR
(301) 492-1169
Charles R. Nichols, NRR
(301) 492-0854 Attachments:
1. Summaries of Recent Reports Concerning Control Room Habitability
2. Figure 1. Schematic Flow Path Diagram of Essential Control Room Heating, Ventilating, and Air Conditioning System at Vogtle 1 and 2
3. List of References
4. List of Recently Issued NRC Information Notices
- SEE PREVIOUS CONCURRENCES
- OGCB:DOEA:NRR
CVHodge
03/31/88 D/DOEA:NRR
CERoss i
5/ /88
- SPLB:DEST:NRR , /8PLB:DEST:NRR
CRNichols
{Craig
03/31/88 C/OGCB:DOEA:NRR
CHBerlinger
05/ /88 SAD/DEST:NRR
AThadani
05/ /88
- PPMB:ARM
TechEd
04/05/88 D/DEST:NRR
LCShao
05/ /88
IN 88-XX
March xx, 1988 No specific action or written response is required by this information notice.
If you have any questions about this matter, please contact the technical
contact below or the Regional Administrator of the appropriate regional office.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contacts:
Vern Hodge
(301) 492-1169
Charles R. Nichols, NRR
(301) 492-0854 Attachments:
1. Summaries of Recent Events Concerning Control Room Habitability
2. Figure 1. Schematic Flow Diagram of Control Room Essential Heating, Ventilating and Air Conditioning System at Vogtle 1 and 2
3. List of References
4. List of Recently Issued NRC Information Notices
OGCB:DOEA:NRR
CVHodge
03/31/88 D/DOEA:NRR
CERossi
03/ /88 A/C/SPLB:DEST:NRR
JWCraig
03/ /88 C/OGCB:DOEA:NRR
CHBerlinger
03/ /88 SAD/DEST:NRR
AThadani
03/ /88 SPLB:DEST:NRR
CRNichols
034X /88 PPMB:ARM
TechEd
03/ /88 D/DEST:NRR
LCShao
03/ /88