ML20235L612
| ML20235L612 | |
| Person / Time | |
|---|---|
| Site: | Zion File:ZionSolutions icon.png |
| Issue date: | 07/10/1987 |
| From: | Gill C, Greger L NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | |
| Shared Package | |
| ML20235L610 | List: |
| References | |
| 50-295-87-05, 50-295-87-5, 50-304-87-05, 50-304-87-5, NUDOCS 8707160762 | |
| Download: ML20235L612 (18) | |
See also: IR 05000295/1987005
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U. S. NUCLEAR REGULATORY COMMISSION
REGION III
Reports No. 50-295/87005(ORSS); 50-304/87005(DRSS)
Docket Nos. 50-295; 50-304
Licenses No. DPR-39; No. DPR-48
Licensee:
Commonwealth Edison Company
P. O. Box 767
Chicago, IL 6G90
Facility Name:
Zion Nuclear Power Station, Units 1 and 2
Inspection At:
Zion, Illinois
Inspection Conducted:
March 2 through June 10, 1987
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Inspector:
C. F. Gill
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Dave ~
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Approved By:
L. R. Greger, Chief
7-4-87
Facilities Radiation Protection
Date
Section
Inspection Summary
Inspection on March 2 through June 10, 1987 (Inspection Reports
No. 50-295/87005(DRSS); No. 50-304/87005(DRSS))
Areas Inspected:
Special, announced inspection of licensee action following
an event involving the release of airborne radioactivity into the control
room and the technical support center (TSC).
Results:
The licensee's failure to have an operable control room makeup air
charcoal adsorber system (Section 5) violated regulatory requirements.
The
appropriate enforcement action for this failure will be determined and
communicated to the licensee by separate correspondence.
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DETAILS.
1.
Persons ' Contacted
@#S. Brzynski, Technical Staff Engineer
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@R..Cascarano, Technical Staff Supervisor
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@#+*P. LeBlond, Zion Nuclear' Licensing Administrator
@+*F. Lentine, Zion Project Engineer, SNED
@#+T. Printz,. Assistant Technical Staff Supervisor
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- J. Rappaport, QA Engineer
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-@#+T. Rieck, Technical Services Superintendent
- C. Schultz, Regulatory Assu'rance Supervisor
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@+M. Turbak, Operating Plant Licensing Director
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- P. Eng, NRC Resident Inspector
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+*L. Greger, NRC/ Region III, Chief, FRPS
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+J. Hayes,,NRC/NRR, Nuclear Engineer
- +*M. Holzmer, NRC Senior Resident Inspect'or
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+*W. Shafer, NRC/ Region III,. Chief, EPRPB
- R. Warnick, NRC/ Region III, Chief, PB No. 1
The inspector also contacted other licensee and contractor employees.
- Denotes those present at a meeting in the NRC/ Region III office on
March'2, 1987.
+ Denotes those present at a meeting in the NRC/ Region III' office on
March 13, 1987.
- Denotes those present at the exit meeting on March 25, 1987.
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@ Denotes those contacted by telephone between March 25 and June 10,_1987.
2.
General
This inspection which began at 12:30 p.m. on March 2,1987, was conducted
to review in depth the circumstances surrounding a September 11, 1986
event in which a release of airborne radioactivity into the auxiliary
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building resulted in noble gases entering both the control room and the
TSC.
The review concentrated on the adequacy the licensee's initial'
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corrective actions and whether the control room ventilation system was
built in accordance with design and met the design requirements of
General Design Criterion 19 of Appendix A to 10 CFR 50,
3.
,L_icensee Action on Previous Inspection Findings
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(0 pen) Unresolved Items (295/86028-01; 304/86028-01):
Control room'and
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TSC ventilation systems unable to meet design requirements.
The adequacy
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of the as-built ventilation. systems and the. licensee's initial corrective-
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actions following the incursion of noble gas into the~ control room and
TSC are discussed in Sections 5 and 6,.respectively.
Because this
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inspection concentrated on whether the as-built control room ventilation
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system met its design requirements, certain portions of this Unresolved
Item will be reviewed further during a future inspection, including:
(1) licensee long term corrective action in response to the September 11,
1986 event, regarding control room habitability, and (2) licensee
corrective action regarding the use of silicone sealant and other
temporary patching material during the 1983 control room emergency air
cleaning system modification and repair.
As discussed in Section 6,
further review of the acceptability of the TSC ventilation system will be
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tracked as a separate Unresolved Item (295/87005-02; 304/87005-02).
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4.
Licensee Event Reports (LER) Followup
Through direct observations, discussions with licensee personnel, and
review of records, the following event report was reviewed to determine
that deportability requirements were fulfilled, immediate corrective
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action was accomplished, and corrective action to prevent recurrence had
been accomplished in accordance with Technical Specifications.
The LER
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listed below is considered closed:
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Units 1 and 2
LER NO.
Description
86035
Minor Radioactive Release into Control
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Room Due to Control Room Relief Damper
Installation Deficiency.
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This LER was reviewed as part of the inspection into the apparent
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inability of the control room and TSC ventilation systems to meet their
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design requirements; these matters are discussed in Sections 5 and 6,
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respectively.
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5.
Inability of the Control Room Ventilation System to Perform Its
Design Requirements
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a.
Event Summary
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On September 11, 1986, while personnel were lowering the level in
the spent resin storage tank, a vent path was established into the
Auxiliary Building from the waste gas system.
Due to relief damper
installation deficiencies in the control room ventilation (PV)
system, low concentrations of airborne radioactivity entered the
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control room.
Because the control room ventilation system was
operating in the accident mode at the time, for reasons stated in
Section 5.b(4) below, the incursion of the noble gases into the
control room raised the question of the adequacy of this system to
meet its design requirements (GDC-19).
On September 15, 1986, as part of the licensee's investigation into
the cause of the event, the relief dampers in the two redundant
return-air fan trains of the PV system were identified as unfiltered
inleakage pathways; these relief dampers were promptly failed closed
and blanked off, thus correcting the problem with that system.
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On November 10, 1986, the licensee reported this event
(LER 86035-00) under 10 CFR 50.73(a:)(2)(v) as a condition which
could have prevented the fulfillment of the safety function of
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systems needed to shutdown the reactor and maintain a safe shutdown
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condition.
According to licensee representatives, the initial
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estimation of the control room unfiltered inleakage pathway was
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approximately 550 cfm, which the licensee initially assumed
indicated the control room emergency air cleanup did not meet its
design requirements (GDC-19).
b.
Event Causation
The following occurrences contributed to the incursion of the
radioactive gases into the control room:
(1) The spent resin storage tank level indication system improperly
showed a partially filled tank when the tank was actually
completely drained, creating the vent path into the auxiliary
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building from the waste gas system.
(2) The gas entered the control room ventilation (PV) system
because the PV system relief dampers were not installed as
designed.
Design drawings M-81 and M-318 showed one relief
damper to be located in discharge ductwork common to both PV
system return fans; however, the installation is such that each
return fan has its own relief damper in its own separate
discharge ductwork.
Whichever return fan is running, an
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unfiltered release pathway exists into PV system through the
common suction ductwork from the other train's relief damper.
The licensee identified relief damper inleakage as the
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predominant pathway of airborne radioactivity into the control
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room during the September 11, 1986 event.
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(3) Inasmuch as no record could be found showing an approved design
change, including field changes, the quality assurance program
implemented by the licensee during construction apparently
failed to identify the failure to construct the control room
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ventilation system in accordance with design documents.
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noted above, a single relief damper is shown on design drawings
M-81 and M-318, but two were installed.
Shortcomings ~in the
quality assurance program allowed this construction error to go
undetected until the licensee's review of the system subsequent
to the September 11, 1986 event.
(4) An opportunity existed for the licensee to discover the
construction error in connection with a review of the control
room ventilation system dictated by NUREG-0737, Item III.D.3.4,
" Control Room Habitability." However, NUREG-0737 allowed
licensees to reference their prior submittals in demonstrating
that their control room ventilation systems could assure
habitability in accordance with NRC design criteria (GDC-19),
as long as those prior submittals reflected current facility
design.
Since the licensee made no major system modification
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since' system installation-in 1971, it was assumed that the
original design drawings reflected the current facility
design. .Had the licensee conducted a detailed walkdown of the
PV system during'the 1981 review of control room habitability-
requirements, it is possible 'that the . relief. damper installation -
error could have been, identified and corrected.
In compliance
with commitments made to the NRC in' response to III.D.3.4, the
licensee made certain modifications and conducted-inleakage
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tests for.the PV system in 1983.
These tests, however, did not
identify the relief damper inleakage pathways.
Also in response to their NUREG-0737, III.D.3.4. commitment,
the licensee'had agreed, in part,.to modify the control room
ventilation system by. January 1, 1984, to tie the normal
outside air intake damper ciosure'to the Safety-Injection
Signal (SIS) from either unit.
Because the-licensee identified
in late December 1983 that'a portion'of the wiring associated-
with the SIS _ modification.did not conform to certain provisions
of IEEE Standard'279'regarding train separation, the-
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modification was disconnected and the control room ventilation
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system run in the accident mode since December 30, 1983'
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(outside air intake isolated and airflow routed through
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charcoal filters) pending' redesign of the modification.
The
control room ventilation system continues to be run in the
accident mode to date.
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(5) An IE Information Notice (86-76) was distributed to all power,
reactor licensees in August 1986.
The licensee's interr.al
response to IE IN 86-76 did not identify the PV relief damper
inleakage pathways.
The licensee's response addressed only
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those specific inleakage pathways addressed by the Information
Notice.
The Information Notice did not specifically address
redundant return air train relief dampers as potential
unfiltered inleakage pathways.
(6) The door between the control room and the TSC was propped open
on September 11, 1986.
The licensee stated that this
configuration was necessary in that outleakage from the control
room was needed to supply ventilation flow to the TSC.
(See
Section 6 for a discussion of TSC ventilation problems.)
The effect of the open door was to produce less than the FSAR
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specified + 0.25 inch wg air pressure, and less.than the
+ 0.125 inch wg air pressure specified by Section 6.4 of the
Standard Review Plan (NUREG-0800), in the control room.
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not expected that the reduced control room pressure had a
significant effect on the unfiltered .inleakage into the control
room in this event because of the large amount of unfiltered
inleakage through the relief. dampers.
However, if this
practice continues, its effect on the long term corrective
actions regarding control room habitability must be addressed.
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c.
Short Term Corrective Action
(1) On September 15, 1986, at about 0900 hours0.0104 days <br />0.25 hours <br />0.00149 weeks <br />3.4245e-4 months <br />, as part of the
ongoing investigation into the cause of the event, the licensee
identified the postulated inleakaje flow path into the control
room ventilation (PV) system via the relief damper in the
non-operating return-air train.
At about 1300 hours0.015 days <br />0.361 hours <br />0.00215 weeks <br />4.9465e-4 months <br />, the
postulated flow path was confirmed using a helium tracer gas
technique.
At about 1700 hours0.0197 days <br />0.472 hours <br />0.00281 weeks <br />6.4685e-4 months <br />, the PV relief dampers were
failed closed and blanked off by sheet-metal held in place by
set-screws and sealed with silicone sealant.
Licensee helium
tests confirmed leak-tightness of this inleakage pathway.
(2) On September 17, 1986, the licensee began a PV system walkdown
to identify any other system / installation discrepancies and
evaluate the effect on system safety function.
On October 30,
1986, the preliminary walkdown/ review reeched the following
conclusions:
Conclusions Regarding The September 11, 1987 Event
The following drawings indicate the PV system was not built
as designed:
M-81 and M-318.
No other PV system installation discrepancies would effect
safety system function.
Preliminary estimates of relief damper inleakage of
550 cfm, based on vendor supplied damper characteristics
without making plant specific flow measurements, led to the
licensee's preliminary conclusion that the control room
ventilation (PV) system could not have met GDC-19
requirement before the relief dampers were sealed.
Conclusions Regarding Other Control Room Habitability Concerns
Potential inleakage pathways exist via PV system drains in
the makeup air filter units and the air handling units.
The outside air intake for the PV and OV systems has two
isolation dampers in series, one of which is a non-bubble
tight damper of undetermined leakage. This configuration
may not conform to the requirements of Standard Review
Plan (SRP) 6.4, Sections II.2.a and II.2.b which are
referenced in NUkEG-0737, Item III.D.3.4.
SRP 6.4,
Section II.2.a, states that dampers used to isolate the
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control zone from adjacent zones or the outside should be
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leaktight.
SRP 6.4,Section II.2.b states that single
failure of an active component should not result in loss
of the system's functional performance.
Thus if the bubble
tight damper should' fail open, the non-bubble tight damper
would be an unfiltered inleakage pathway; however, SRP 6.4
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also details acceptance criteria for a damper repair
alternative which would allow the installation of a
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non-bubble tight damper if certain conditions are met.
The PV system was not adequately isolated from the OV
system.
An outside air duct connects the PV and OV air
handling units.
This path is isolated by a non-bubble
tight damper.
Another outside air path connects the
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PV air handling units to the OV lab hoods supply fan; this
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path is isolated downstream of the fan by a nor-bubble
tight damper.
Because of the licensee's failure to
adequately isolate the PV and OV systems, any fcilure
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which causes the 0V system to become contaminated will
subsequently contaminate the PV system and the control
room.
The PV system has been temporarily blanked off from
the OV system.
The hot and cold laboratory supply fan is designed to
continue operation when the PV and OV systems are failed
in the accident mode; this would create a negative
pressure in the normal intake duct for the PV and
OV systems, thus increasing the potential for unfiltered
inleakage into both the control room and TSC.
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The closing of the PV system relief dampers removes the
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capability of relieving excess air from the system; thus,
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the PV system should be modified from economizer systems
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to minimum outside air systems.
It appears that smoke
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purging of the control room would require that the doors
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to the turbine building be opened and portable purge fans
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be used.
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The pressure sensing instrunientation for the control room
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is inadequate.
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(During a plant tour on March 25, 1986, the inspector noted
the control room panel pressure gauge read + .05 inch wg
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and
.05 inch wg with the door between the control room
and the TSC closed and open, respectively.
The licensee
stated that the guage was in error, was to be corrected,
and that when the door between the control room and the
TSC was closed, independent measurements had demonstrated
that the control room was being maintained at a pressure
of, at least, + 1.25 inch wg with respect to surrounding
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areas (which would satisfy the criterion of Standard Review
Plan 6.4).
Tiie control room pressure is presently
specified to be + .25 inch wg, according to Section 9.10
of the FSAR.
An inadequate control room pressure
measurement system and a general misunderstanding of the
value of the required control room positive pressure inay
have contributed to the inadequate maintenance of the
control room gas-boundary.)
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With the door open between the control room and the TSC,
the PV system is unable to adequately pressurize the
control room.
The licensee has ensured that procedures
adequately specify the requirements to close the door
between the control room and TSC in the event of an
accident.
(3) On March 11, 1987, helium tracer gas leakage tests of the
PV system indicated, according to licensee personnel, that the
total system unfiltered inleakage values were 8.6 and 14.2 cfm
with the relief dampers sealed, depending on which return-air
fan was operating.
However, the helium tracer gas procedure
used by the licensee was previously found to be unacceptable by
the NRC.
The licensee had been informed of the unacceptability
of this test by the inspector.
d.
Long Term Corrective Action
(1) Based on the PV system walkdown/ review, the licensee is
considering several actions to enhance PV system performance,
including the addition of bubble-tight dampers (See Section 5.c,
Item (2)).
(2) The licensee is investigating the feasibility of permanent
modifications to separate the PV system from the OV system.
(3) Revision of the plant drawings to accurately reflect as-built
conditions of the PV system.
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(4) The licensee has committed to the NRC that a test will be
conducted which demonstrates GDC-19 requirements are met after
PV system modifications are completed and the NRC concurs on the
acceptability of the test procedure.
(5) Ensure that the control room gas control boundaries are, at
least, + .125 inch wg with respect to adjacent areas and proper
instrumentation is installed to verify that pressure
difference.
The acceptance criterion of the Standard Review
Plan (NUREG-0800), Section 6.4 is + .125 inch wg; the present
criterion of FSAR Section 9.10 is + .25 inch wg.
This
inconsistency will be reconciled by the licensee.
(6) The present blank-off of the PV relief dampers may not be the
final configuration.
The leak-tightness of the present
modification involves the use of sheet-metal, set-screws, and
silicone sealant; the NRC informed the licensee in August 1985
that the use of silicnne sealant and other temporary patching
material on the PV system is unacceptable.
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e.
Safety' Significance
(1) Radioactive Airborne Release of September 11,'1986
The licensee estimates'that 4500 cubic feet of. waste gas were
vented into the auxiliary building from the waste gas system on.
September 11, 1986, while personnel were lowering the level'in-
the spent. resin storage tank.
The licensee reported that-
approximately 8.2 curies.of noble gas were released during the-
event.
The maximum stack release rate reported by the licensee;
was 2.4 percent of Technical Specifications.
Due to design /
installation deficiencies in ventilation systems, the airborne-
radioactivity entered the TSC.and the control room.
There
were no contaminations of plant personnel or. building
evacuations due to this incident. . A release of this magnitude
does not represent a significant health.or'sefety hazard.
(2) PotentialEffectonControlRoomOperators'forDesignBasis,.
, Accident-
The control room ventilation (PV) system had been operating in
the accident mode since December 30, 1983; therefore, the
incursion of the noble gases into the control room on
September 11,'1986, raised the question of the' adequacy of this
system to meet its design requirements (GDC-19).under design
basis accident (DBA) conditions.
On September 15, 1986, as part of.the licensee's investigation
into the cause of the event, the relief dampers in the two
redundant return-air fan trains of the control room ventilation
system were identified as unfiltered inleakage pathways.
These relief dampers were promptly failed closed and blanked
off, thus correcting the problem with the relief dampers which
had existed since initial plant operation.
The licensee measured inleakage values of 154 cfm.and 236 cfm
for Train A and Train B, respectively, without the relief
dampers blanked off.
Based on the licensev s--1981 submittal
to the NRC for TMI Action Item III.D.3.4, performed for the
licensee by Entech, potential thyroid doses of 199 rem and
293 rem are predicted under DBA conditions for.the respective
measured unfiltered inleakages.
These values greatly exceed the-
GDC-19 thyroid dose limit (30 rem).
However, during the.
inspector's evaluation of the event the licensee informed him
that their 1981 Entech evaluation was' unnecessarily. conservative,
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and the licensee subsequently had Sargent & Lundy (S&L) perform
a " realistic" evaluation of control room operator' doses based
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on the measured inleakage values.
The evaluation eventually
resulted in calculated thyroid doses of 10.3 rem and 15.2 rem,
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which are within GDC-19 limits; these.results transmitted from
S&L to the licensee by a letter dated April 2, 1987 (attached).
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Later, by letter dated May 19, 1987 (attached), the licensee
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acknowledged to the NRC Region III Regional Administrator that
the previous calculation included a nonconservative assumption
which might increase the calculated dose by as much as 500%.
In that same letter, the licensee contended that (for
unspecified reasons) they still believed the as-built Zion
com rol room ventilation system met GDC-19 requirements.
By memorandum dated April 15, 1987, NRC Region III requested
assistance from NRR in evaluating the adequacy of the Zion
as-built control room air cleaning system, taking into account
the identified pathways for unfiltered inleakage of airborne
radioactivity.
Specifically, Region III asked NRR to evaluate
the acceptability of the licensee's " realistic" evaluation and,
if the evaluation was not acceptable, to determine the correct
accident doses.
NRR replied in a June 4, 1987 memorandum
(attached) which stated the following conclusions:
The " realistic" analysis is not consistent the Standard
Review Plan (SRP), and since the deviations from the SF.?
were not justified on a plant specific basis by the
licensee, the licensee analysis is unacceptable.
Based on the SRP criteria and the specified damper
leakages, the thyroid dose in the control room under
design basis accident conditions was calculated to be
about 380 rems using Train B and 270 rems using Train A.
The Zion control room ventilation system did not meet
GDC-19 prior to the relief dampers being failed closed and
blanked-off.
If the relief dampers were replaced with zero leakage
dampers, the thyroid dose would be 50 rems, and the
licensee's control room ventilation system still would not
meet GDC-19 (even with the relief dampers failed closed
and blanked-off).
The licensee and NRR are currently resolving the issue regarding
the apparent continuing failure of the current Zion control
room ventilation system to meet GDC-19.
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f.
Regulatory Requirements
Appendix B to 10 CFR 50 defines the required quality assurance
criteria for nuclear power plants to assure safe operation,
including quality assurance requirements for construction of systems
that mitigate the consequences of postulated accidents that could
cause undue risk to the health and safety of the public.
These
criteria require that changes to plant design be subject to design
control measures and be approved.
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Technical Specification 3.17.1-requires that the control' room makeup
air charcoal adsorber system be operable unless the system is
restored to_ operable status within seven days, or be.in'at least hot-
standby within the next six hours-and be.in cold shutdown within the
following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br /> from the date1that the system is made inoperable.
General Design Criterion 19 of Appendix A to 10 CFR 50 requires
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that the control room be provided with' adequate radiation protection
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.to permit access and occupancy.of.the control room under_ accident
conditions without personnel receiving radiation exposures.in excess
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of five tem whole body,.or its equivalent to any.part of the body,
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for the duration of the accident.
Standard Review Plan (NUREG-0800)
Section 6.4, " Control Room Habitability Review," states that a
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thyroid dose of.30 rem is compatible with the GDC-19 dose
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guideline.
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The basis for Techn'ical Specification'3.17 states that.the plant-
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ventilation systems are as described in FSAR Section 9.10.
In
response to FSAR Question 9.3 on Section 9.10, the licensee provided
an' evaluation which indicated that the control room ventilation
system design is such that LOCA thyroid doses will not exceed 30 rem'
to control room personne1'for the duration of the accident,
including. dose received during. ingress and' egress. As stated above,
a thyroid dose of 30 rem is compatible with the GDC-19 dose
guideline.
In violation of the above regulatory requirements, the control. room
makeup air charcoal adsorber system was apparently inoperable since
plant startup until September 15, 1986, because of the relief damper
arrangement in the system.
This arrangement, which was contrary to
plant design (unapproved change), would have resulted in unfiltered
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inleakage under design basis accident conditions in excess of.that
specified in GDC-19 (i.e. , thyroid doses of approximately,270 to
380 rem, which significantly exceed the specified 30 rem).
(295/87005-01; 304/87005-01)
6.
Inability of'the TSC Ventilation System to Perform Its Design Requirements
Design Requirements
a.
Event Summary
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On September 11, 1986, while personnel were lowering the level in
-the spent resin storage tank, a vent path was established into the
Auxiliary Building from the. waste gas system.
Due to damper
operational. deficiencies in the computer and miscellaneous rooms
ventilation (OV) system, low concentrations of airborne
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radioactivity entered the TSC.
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On. September 12, 1986, as'part of the licensee's investigation
into the cause of the event, the inleakage into the TSC was-
determined to be due to a partially open relief. damper in the
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OV system; this relief damper and an open bubble tight damper in
series with the relief damper were promptly failed closed, thus
correcting the problem with that system.
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On November 21, 1986, the licensee informed the resident inspector
that their computer and miscellaneous rooms ventilation (OV) system,
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which supplies ventilation air to the TSC, could not be demonstrated
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to meet its design criteria.
The licensee found that some of the
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rooms supplied by the OV system were not at a positive pressure with
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respect to adjoining areas, resulting in the potential for air
leakage into the OV system from the Auxiliary Building.
In the
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event of high airborne activity following an accident, the TSC could
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become uninhabitable.
b.
Event Causation
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The following occurrences contributed to the incursion of the
radioactive gases into the TSC:
(1) The spent resin storage tank level indication system improperly
showed a partially filled tank when the tank was actually
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completely drained, creating the vent path into the auxiliary
'
building from the waste gas system.
(2) The computer and miscellaneous rooms ventilation (OV) system
inleakage problem resulted when a partially completed
modification was not left in a condition that would fulfill the
design intent of the 0V system.
In late 1982, an isolation
(bubble-tight) damper was installed in series with the OV
relief damper, but through inadequate administrative control
over the partially completed modification, the OV relief damper
and the isolation damper were not failed closed.
During the
September 11, 1986 event, the OV system was being operated in a
configuration which created a negative pressure in the relief
damper ductwork, thus creating an unfiltered inleakage pathway
into the TSC.
(3) Insufficient leak-tightness of the TSC gas-control boundary also
contributed to lack of an adequate positive pressure in the
TSC.
Discussion with appropriate plant personnel indicated
that before the evaluation of the OV system after the
September 11, 1986 event, they were unaware that, under DBA
conditions, the TSC habitability requirement necessitates an
adequate positive pressure TSC gas-control envelope.
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c.
Short Term Corrective Action
(1) On September 12, 1986, at about 1200 hours0.0139 days <br />0.333 hours <br />0.00198 weeks <br />4.566e-4 months <br />, a postulated
flow path between the auxiliary building and the TSC
ventilation (OV) system was verified to exist via the TSC
pressure relief damper flow path.
At about 1600 hours0.0185 days <br />0.444 hours <br />0.00265 weeks <br />6.088e-4 months <br />, this
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inleakage pathway was eliminated by failing closed the
appropriate dampers.
Licensee helium tracer gas tests
reportedly confirmed leak-tightness of this inleakage pathway.
(2) On September 17, 1985, the licensee began an OV system walkdown
to identify other system / installation discrepancies and
evaluate the effect on system safety function.
On October 30,
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1986, the preliminary walkdown/ review reached the following
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conclusion:
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Although acceptance testing of the TSC construction
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modification began on September 8, 1986, the TSC HVAC
performance criteria were not adequately communicated to
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the field.
Specifically, it was not identified by the
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station personnel that the TSC was to be maintained at a
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positive pressure by the OV system.
By design, the
section of the OV ductwork containing the relief damper,
,
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should have been under positive pressure.
On September 11, 1986, the OV system relief damper was in
a partially open position which allowed between 5700
and 9600 cfm of unfiltered auxiliary building air to enter
the OV system.
Also on that date, the bubble-tight
isolation damper in series with the relief damper was
open. With the ductwork under positive pressure, both
dampers should have been failed closed.
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Potential inleakage pathways exist via 0V system drains in
the makeup air filter units and the air handling units.
Insufficient leak-tightness of the TSC gas-control
boundary contributed to the lack of a positive pressure in
the TSC.
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The installed OV system pressurized boundary isolation
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dampers may not be acceptable with regards to current
licensing requirements.
The hot and cold laboratory supply fan is designed
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to continue operation when the PV and OV systems are
failed in the accident mode; this would create a
negative pressure in the normal intake duct for the PV
and OV systems, thus increasing the potential for
unfiltered inleakage into both the control room and TSC.
The closing of the 0V system relief damper removes the
capability of relieving excess air from the system; thus,
the OV system should be modified from economizer systems
to minimum outside air systems.
The OV system is unable to pressurize the TSC.
13
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,
,
The following drawings indicate the 0V system was not
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built as designed: .M-77 and M-316.
(3) On November 18, 1986,- Sargent & Lundy presented the licensee.
with the report of the. preliminary results of.their OV system.
walkdown/ review effort.' .This process ~ identified positive
pressure.as a.TSC requirement.
(4) On November 21, 1986, OV system flow / testing modeling was
initiated to determine the feasibility and identify. actions to
achieve' positive pressure within the TSC.
Also.the. licensee
informed the' resident inspector that the OV system could not be
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demonstrated to' meet its design criteria; in the event of high
!
-airborne radioactivity following an accident, the TSC could
become uninhabitable (Inspection Reports No. 50-295/86028(DRP);
No. 59-304/86028(DRP)).
.(5) On December 3, 1986, the licensee sent to all GSEP. Recovery
Managers a memorandum.which stated the. Zion TSC cannot be
maintained at a positive pressureand Zion Procedure
No. EPIP 410-1, "On-Site Support Centers," addresses. actions to,
be taken if the TSC becomes uninhabitable.
(6) On March 3, 1987, Sargent & Lundy provided the licensee with.
the results of the OV HVACLtesting. computer'modeling effort.
Included in this report is a preliminary list of recommended.
actions to increase TSC pressure.
(7)' Between March 3 and 11, 1987, work packages were initiated on--
twelve OV system short term items; seven additional items were-
also evaluated, including the possibility of increasing TSC
makeup air flow.
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d.
Long Term Corrective Action
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(1) Based on the OV system walkdown/ review, the licensee is
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considering several actions to enhance OV system performance,
including the addition of bubble-tight dampers (See Section 6.c,
Item (2)).
(2) The licensee is investigating the feasibility of permanent
modifications to separate the PV system from the-0V. system.
(3) Revision of the plant drawings to accurately reflect as-built
conditions of the OV systems.
(4) On January 19, 1987, the licensee committed to NRR to construct
a new TSC for the Zion Station.- The licensee expects to
provide NRR with the construction schedule for the new TSC by-
July 1, 1987.
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e.
Safety Significance
(1) Radioactive Airborne Release of September 11, 1986
As stated in Section 5.e, a release of this magnitude does not
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represent a significant health and safety hazard.
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(2) Potential Effect on TSC Personnel for Design Basis Accident
Because the TSC modifications were not completed on
September 11, 1986, and the licensee has committed to the NRC to
build a new TSC, the requirements of GCD-19 apparently are not
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currently applicable.
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f.
Conclusions
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The modification of the OV system.and the sealing of the current TSC
gas-control envelope will be reviewed further during future
,
inspections, in part, to ensure that the completed modifications
{
meet GDC-19.
The new proposed TSC will also be reviewed during
future inspections to ensure that all regulatory requirements and
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licensee commitments are met.
This matter is considered an
Unresolved Item (295/87005-02; 304/87005-02).
7.
Exit Meeting
The inspector met with licensee representatives (denoted in Section 1) in
the NRC Region III office on March 2 and 13, 1987, at the conclusion of
the site inspection on March 25, 1987, and by telephone through June 10,
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1987.
The inspector summarized the scope and findings of the inspection,
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including the unresolved item and the apparent violation.
The inspector
also discussed the likely informational content of the inspection report
with regard to documents or processes reviewed by the inspector during
the inspection.
The licensee did not identify any such documents /
processes as proprietary.
Attachments:
1.
Ltr dtd 04/02/87 from
B. Schwartz to F. G. Lentine
2.
Ltr dtd 05/19/87 from
P. C. LeBlond to A. B. Davis
3.
Ltr dtd 06/04/87 from
F. J. Congel to J. A. Hind
.
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SARGENT & LUMDT
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ENGINEE343
rovNOcc ie ,e-
55 CAST MONROE STRECT
CHICAOO, lLLINOIS 60603
(3823 269 2000
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TwX 9fOa28t*2607
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April 2, 1987
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Project No. 7897-00
Commonwealth Edison Company
Zion Nuclear Power Station - Units 1&2-
Best Estimate Control Room
Habitability Analysis
Revision 1
Reference:
r etter B. C. Schwartz (S& L) to
F. G. Lentine (CECO) dated March 12,
1987 "Best Estimate Control Room
Habitability Analysis"
Mr.
F. G.
Lentine
Station Nuclear Engineering Division
Commonwealth Edison Company
P.O. Box 767 - 35 FNW
Chicago, IL
60690
Dear Mr. Lentine:
At your request Sargent & Lundy has recalculated the best
estimate control room habitability calculation under the
_
following additional conditions and assumptions:
Primary Containment spray in operation for 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> which
o
depleted the organic and particulate iodine species in that.
period
Zion specific occupancy factors related to 8. hours per day
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for 7 days with 2 days of f for 30 days
The maximum measured integrated leak' rate for either unit,-
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over the last 14 years of .035%/ day for-the first 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />s-
and .0175% for'the duration, a total of.30 days was used.
the following conditions and assumptions were previously stated
.n the referenced letter and have also been used in the
- alculation:
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SARGENT& LUNDY
E N GIN E E MS
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CHICAGO
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Mr. F. G.
Lentine
April,2, 1987
' Commonwealth Edison Company
Page 2
Primary Containment forced circulation = 1.9
5
PrimaryContainmentfreevolume=2.715x10gx30
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cfm
e
ft
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Primary Containment: sprayed volume fraction _=__.3239__-
_
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Operating power is'102% of 3250 MWth
Initial airborne, iodine = 100% of the adjusted gap activity
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as defined in FSAR Table A.2-2
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Iodine species 95.5% elemental, 24 particulate and 2.5%
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organic
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Spray decontamination factor - 200 elemental
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Basic dose modeling for the turbine and auxiliary'bu'ilding
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is the same as that in the FSAR Question 9.3, Amendment 17
- 1971
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154 and 236 cfm of unfiltered inleakage from A&B train
auxiliary building' dampers respectively
Murphy Campe wind direction factors
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9
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Gamma whole. body-and beta skin doses were not recalculated as the
values stated in the reference letter were well within regulatory
3
limits.
Tables 1 and 2 show calculated thyroid doses for
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containment leakage of .1% and .035% per day for the first day
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and 50% of that for the duration, 30 days total.
From Table 2,
with the above stated conditions and assumptions, the calculated
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thyroid doses are below the GDC 19 limit of 30 rem.
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Yours very truly,
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B. Schwartz
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Senior Shielding
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'C.
Project Engineer
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!lg!
BS:lrg
In duplicate
Enclosure - All Recipients
Copies:
P. C.
LeBlond
R. J. Mazza
J.
S.
Loomis
J. C. Daum
D.
N.
Diotallevi
J. Gering
!
R.
A.
Hameetman
G.
P.
Lahti
J.
M. Rich
NSLD File 4C4-Al
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TABLE 1
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Control 1<oom 30 Day Dose Summary Using Zion
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Control Room Occupancy Murphy Campe Wind Direction Factors and'
)
Design Containment Leakage
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Control
. Control Room
Control
Control Room 30 Day'
. Room
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Infiltration
Room
Dose, Rem,
30 Day
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Rate, cfm, from
Filter
Contributions from the
Tetal
Aux.
Efficiency,
Aux.
Turbine
Dose,.-
Bldg.
Percent
Dose Type
Bldg.
Bldg.
154
99.99
Thyroid
29.4
.01
_29.4
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236
99.99
Thyroid
43.3
0.0
43.3
TABLE 2
Control Room 30 Day Dose Summary Using Zion Control
Room Occupancy Murphy Camoe Wind Direction'and 14 Year
Maximum Integrated Containment Leak Rate
Control
.
Control Room
Control
Control Room 30 Day'
Room
Infiltration
Room
Dose, Rem,
30 Day
Rate, cfm, from
Filter
Contributions from the
Total
Aux.
Efficiency,
Aux.
Turbine
Dose,
Bldo.
Percent
Dose Type
Bldg.
Bldg.
154
99.99
Thyroid
10.3
.01
10.3
-1
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236
99.99
Thyroid
15.2
0.0
15 '. 2 '
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Commonwealth Edison
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One First National Plaza. CNeago. !!hnois
7;
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Address Reply to. Post Offca Box 767
s'%j CNeago, Ithnois 60690 0767
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PRf02in tourtro
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Q"
gruul
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May 19, 1987
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G V) * I MR. b
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Mr. A. Bert Davis
mg
Regional Administrator
U.S. Nuclear Regulatory Commission
Region III
~799 Roosevelt Road
Glen Ellyn, IL 60137
Subject: Zion Nuclear power Station Units 1 and 2
i
Main Control Room HVAC
NRC Docket Nos. 50-295 and 50-304
Dear Mr. Davis:
Copies of four calculations involving the Zini Control Room
ventilation system were provided to V.D. Shafer on April 6, 1987, as part of
the ongoing inspection regarding the September 11, 1986, radioactive release
at Zion Station. These calculations were performed at the request of C.F.
Gill of your office.
Specifically, calculation No. ZI-6-87 was performed to estimate the
postulated 30-day Main Control Room doses that might have been received had
a LOCA occurred at Zion Station prior to the September 11, 1986 event.
This
calculation, when adjusted for the maximum integrated containment leak rate,
yielded a maximum 30-day Control Room dose of 15.2 Rem. This is well below
the 10 CFR 50, Appendix A, GDC 19 limit of 30 Rem. This dose projection is
intended to be a conservative, but realistic estimate of the actual doses
that control room personnel could have received.
This calculation also assumed the operation of a single Auxiliary
Building Supply Fan.
This condition is representative of approximately 50%
of Zion's operating history. The remainder typically involved operation
with no supply fans running, resulting in no active air supply to the
Auxiliary building.
This results in roughly a factor of six reduction in
Auxiliary Building flowrate.
An internal Commonwealth Edison Company technical review has
identified that the dose model being utilized is highly sensitive to changes
in auxiliary building flow rate. This model yields total doses that are
inversely proportional to Auxiliary Building air flowrate. Thus, the model
would predict a six-fold increase in the total control room doses received
in response to a six-fold reduction in air flow.
.h
gSMW
g
MAY 2 0198n
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A.B. Davis
-2-
May 19, 1987
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This situation has been carefully reviewed by Commonwealth Edison
1
personnel and their consultants. Commonwealth Edison company believes that
the dose model's sensitivity to auxiliary building flowrate does not
represent an actual physical effect. Thus, it would not yield an accurate
I
estimate of the actual doses that could have been received during the
I
low-flow conditions.
In addition, the postulated effects of the airflow reduction on the
calculation could be compensated for by the removal of additional,
unnecessary conservatism and through the use of more advanced computer
modelling techniques. This information provides confidence that the
,
previously supplied 30-day dose estimate of 15.2 rem remains a realistic,
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but yet conservative estimate of the actual doses that could have been
received during a postulated LOCA.
J
Based upon the above information, commonwealth Ediaan has no
further plans to refine the control room dose calculations in support of the
september 11, 1986, event. The estimate of 15.2 rem received over a 30-day
time period provides a reasonable assessment of the safety significance of
the ventilation discrepancies discovered on September 11, 1986.
This information was discussed with W.D. Shafer on April 14, 1987.
If any further questions arise regarding this matter, please direct them to
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this office.
very truly yours,
h
$<
P.C. LeBlond
Nuclear Licensing Administrator
cc: Resident Inspector
J.A. Norris - NRR
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3068K
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