ML20235N148
| ML20235N148 | |
| Person / Time | |
|---|---|
| Site: | Zion File:ZionSolutions icon.png |
| Issue date: | 10/02/1987 |
| From: | Davis A NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | |
| Shared Package | |
| ML20235N058 | List: |
| References | |
| 50-295-87-5, 50-304-87-5, EA-87-105, NUDOCS 8710060405 | |
| Download: ML20235N148 (2) | |
Text
_ _ _ _ _ _ _ _ _ _
AND PROPOSED IMPOSITION OF CIVIL PENALTY Commonwealth Edison Company Docket Nos. 50-295; 50-304 Zion Generating Station Licenses No. DPR-39; No. DPR-48 Units 1 and 2 EA 87-105 As a result of an NRC inspection conducted during the period March 2 through June 10, 1987, a violation of NRC requirements was identified.
In accordance with the " General Statement of Policy and Procedure for NRC Enforcement Actions,"
l 10 CFR Part 2, Appendix C (1987), the Nuclear Regulatory Commission proposes to impose a civil penalty pursuant to Section 234 of the Atomic Energy Act of 1954, as amended (Act), 42 U.S.C. 2282, and 10 CFR 2.205.
The particular violation and associated civil penalty are set forth below:
10 CFR 50.34(b) requires, in part, that the licensee submit a final safety analysis report that describes the facility.
10 CFR 50.59 requires, in part, that changes made to the facility as described in the final safety analysis report be evaluated in accordance with 50.59(a) to determine, in part, if an unreviewed safety question exists.
Figure 9.10.2-1 of the Zion Station Updated Final Safety Analysis Report (UFSAR) 7'.:
illustrates the design configuration of the control room sent!1ation system.
o Contrary to the above, the control room ventilation system as described in Figure 9.10.2-1 of the UFSAR did not reflect the as-built system as required by 10 CFR 50.34(b).
The system as-built contained a different damper configuration than that described in the UFSAR which resulted in unfiltered inleakage pathways.
The deviation between the UFSAR and the as-built system was not evaluated in accordance with 10 CFR 50.59.
This is a Severity Level III violation (Supplement I).
Civil Penalty - 550,000.
Pursuant to the provisions of 10 CFR 2.201, Commonwealth Edison Company (Licensee),
is hereby required to submit a written statement or explanation to the Director, Office of Enforcement, U.S. Nuclear Regulatory Commission, within 30 days of the date of this Notice.
This reply should be clearly marked as a " Reply to a Notice of Violation" and should include:
(1) admission or denial of the alleged violation, (2) the reasons for the violation if admitted, (3) the corrective steps that have been taken and the results achieved, (4) the corrective steps that will be taken to avcid further violations, and (5) the date when full compliance will be achieved.
If an adequate reply is not received within the time specified in this Notice, an order may be issued to show cause why the license should not be modified, suspended, or revoked or why such other action as may be proper should not be taken.
Consideration may be given to extending the response time for good cause shown.
Under the authority of Section 182 of the Act, 42 U.S.C. 2232, this response shall be submitted under oath or affirmation.
8710060405 871002 DR ADOCK 05000295 PDR
OCT 2 1987 Within the same time as provided for the response required above under 10 CFR 2.201, the Licensee may pay the civil penalty by letter to the Director, Office of Enforcement, U.S. Nuclear Regulatory Commission, with a check, draft, or money order payable to the Treasurer of the United States in the amount of civil penalty proposed above, or may protest imposition of the civil penalty l
o-in whole or in part by a written answer addressed to the Director, Office of Enforcement, U.S. Nuclear Regulatory Commission.
Should the Licensee fail to j
answer within the time specified, an order imposing.the civil penalty will be l
1ssued.
Should the Licensee elect to file an answer in accordance with 10 CFR 2.205 protesting the civil penalty, in whole or in part, such answer should be clearly marked as an " Answer to a Notice of Violation" and may:
(1) deny the violation listed in this Notice in whole or in part, (2) demonstrate extenuating circumstances, (3) show error in this Notice, or (4) show other reasons why the penalty should not be imposed.
In addition to protesting the-civil penalty, such answer may request remission or mitigation of the penalty.
In requesting mitigation of the proposed penalty, the five factors addressed in Section V.B of 10 CFR Part 2, Appendix C (1987), should be addressed. Any written answer in accordance with 10 CFR 2.205 should be set forth separately from the statement or explanation in reply pursuant to 10 CFR 2.201, but may incorporate parts of the 10 CFR 2.201 reply by specific reference (e.g., citing page and paragraph numbers) to avoid repetition.
The attention of the Licensee is directed to the other provisions of 10 CFR 2.205, regarding the procedure for imposing a civil penalty.
Upon failure to pay any civil penalty due which subsequently has been determined in accordance with the applicable provisions of 10 CFR 2.205, this matter may be referred to the Attorney General, and the penalty, unless compromised, remitted, or mitigated, may be collected by civil action pursuant to Section 234c of the Act, 42 U.S.C. 2282c.
The responses to the Director, Office of Enforcement, noted above (Reply to a Notice of Violation, letter with payment of civil penalty, and answer to a Notice of Violation) should be addressed to:
Director, Office of Enforcement, U.S. Nuclear Regulatory Commission, ATTN:
Document Control Desk, Washington, DC 20555 with a copy to the Regional Administrator, U.S. Nuclear Regulatory Commission, 799 Roosevelt Road, Glen Ellyn, Illinois, 60137, and a copy to the NRC Resfdent Inspector at Zion.
FOR THE NUCLEAR REGULATORY COMMISSION (2y 500%
A. Bert Davis Regional Administrator Dated a Glen Ellyn, Illinois this day of.0ctober 1987
1 U. S. NUCLEAR REGULATORY COMMISSION REGION III Reports No. 50-295/87005(DRSS); 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 60690 Facility Name:
Zion Nuclear Power Station, Units 1 and 2 Inspection At:
Zion, Illinois Inspection Conducted:
March 2 through June 10, 1987 Inspector:
C. F. Gill
/0 c[7 DaYe Approved By:
L. R. Greger, Chief 7-M -8 7 Facilities Radiation Protection Date Section Inspection Summary Inspection on March 2 throuDb June 10, 1987 (Inspection Reports No. 50-295/87005(DR55); 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 supp?rt 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 cor.vnunicated to the licensee by separate correspondence.
W}.:. & '
< r s5 hk
DETAILS l
l 1.
Persons Contacted 1
i NS. Brzynski,' Technical Staff. Engineer
- R. Cascarano, Technical Staff Supervisor N+*P. LeBlond, Zion Nuclear Licensing Administrator
@+*F. Lentine, Zion Project Engineer, SNED N+T. Printz, Assistant Technical Staff Supervisor
- J. Rappaport, QA Engineer l
W+T. Rieck, Technical Services Superintendent
- C. Schultz, Regulatory Assurance Supervisor
@+M. Turbak, Operating Plant Licensing Director.
i
- P. Eng, NRC Resident Inspector
+*L. Greger, NRC/ Region III, Chief, FRPS i
+J. Hayes, NRC/NRR, Nuclear Engineer
- +*M. Holzmer, NRC Senior Resident Inspector I
+*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.
1
+ 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.
9 Denotes those contacted by telephone between March 25 and June 10, 1987.
2.
General This inspection which began at 12:30 p.m. on Marcb 2,1987, was conducted to review in depth the circumstances surrounding t ieptember 11, 1986 event in which a release of airborne radioactivity into the auxiliary building resulted in noble gases entering both the control room and the TSC.
The review concentrated on the adequacy the licensee's initial corrective actions and whether the control room ventilation system was built in accordance with design and met the design requirements of i
General Design Criterion 19 of Appendix A to 10 CFR 50.
3.
Licensee Action on Previous Inspection Findings (0 pen) Unresolved Items (295/86028-01; 304/86028-01):
Control room and
'ISC ventilation systems unable to meet design requirements.
The adequacy of the as-built ventilation systems and the licensee's initial corrective l
actions following the incursion of noble gas into the control room and TSC are discussed in Sections 5 and 6, respectively.
Because this inspection concentrated on whether the as-built control room ventilation 2
e e
Lj' 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 II, 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 l
cleaning system modification and repair.
As discussed in Sectinn 6, further review of the acceptability of the TSC ventilation system will be tracked as a separate Unresolved Item (295/87005-02; 304/87005-02).
4.
Licensee Event Reports (LER) Followup Through direct _ observations, discussions with licensee personnel, and review of. records, the following even,t report was reviewed to dettraine that deportability requirements were fulfilled, immediate corrective
-action was accomplished, and corrective action to prevent recurrence had been accomplished in accordance with Technical Specifications.
The LER listed below is considered closed:
Units 1 and 2 LER NO.
Description 86035 Minor Radioactive Release into Control Room Due to Control Room Relief Damper Installation Deficiency.
This LER was reviewed as part of the inspection into the apparent inability of the control room and TSC ventilation systems.to meet their design requirements; these matters are discussed in Sections 5 and 6, respectively.
5.
Inability of the Control Room Ventilation System to Perform Its Design Requirements a.
Event Summary 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 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) telow, 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.
3
On November 10, 1986, the. licensee reported this event (LER 86035-00) under 10 CFR 50.73(a)(2)(v) as a condition which coulo have prevented the fulfillment of the safety function of systems needed to shutdown the reactor and maintain a safe. shutdown condition. According to licensee representatives, the initial estimation of the control room unfiltered inleakage pathway was 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 fo11owing 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 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 itt, own separate discharge ductwork.
Whichever return fan is running, an 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 predominant pathway of airborne radioactivity into the control l
room during the September 11, 1986 event.
(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 ventilation system in accordance with design documents.
As 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 1
4 J
(
0 i
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 bee.. 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 tests for the PV system in 1983.
These tests, however, did not ident fy the relief damper inleakage pathways.
Alsojin response to their NUREG-0737, III.D.3.4. commitment, the licensee had egreed, in part, to modify the control room ventilation system by January 1, 1984, to tie the normal outside air intake damper closure to the Safety-Injectiori 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 modification was disconnected and the control room ventilation system run in the accident mode since December 30, 1983 (outside air intake isolated and airflow routed through charcoal filters) pending redesign of the modification.
The control room ventilation system continues to be run in the accident mode to date.
(5) 'An IE Information Notice (86-76) was distributed to all power reactor licensees in August 1986.
The licensee's internal response to IE IN 86-76 did not identify the PV relief damper inleakage pathways.
The licensee's response addressed only 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, 1985.
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 specified + 0.25 inch wg air pressure, and less than the 0.125 inch wp air pressure specified by Section 6.4 of the 4
Standard Review Plan (NUREG-0800), in the control room.
It is not expected that the reduced control room pressure had a 1
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 l
actions regarding control room habitability must be addressed.
l l
i l
5
)
- ..F l
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 inleakage flow-path into the control room ventilation (PV) system via the relief darcper 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 helim 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 9etal held in place by 1
set-screws and 4e41ed with silicone sealant.
Licenree he'iium
(
tests confirmed 'ieak-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 reached the following conclusions:
I Conclusions Regarding The September II, 1987 Event j
The following drawings indicate the PV system was not built I
as designed:
M-81 and M-318.
I No other PV system installation discrepancies would effect safety s3/ stem function.
Prehmiriary 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.
)
)
Concludens Regarding Other Control Room Habitability Concerns Potential inleakage pathwnys e<ist via PV system drains in
)
the makeup air filter units and the air handling units.
r 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, Sutions II.2.a and II.2.b which are referenced in NUREG-0737, Item III.D.3.4.
SRP 6.4,Section II.2.a, states that dampers used to isolate the control zone from tidjacent zones or the outside should be i
leaktight.
SFP 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 1
"s 6
i J
also details acceptance criteria for a damper repair alternative which would allow the installation of a non-bubble tight damper if certain conditions are met.
The PV dstem was not adequately isolated from the OV system.
An outside air duct connects the PV and OV air handling units.
Thir, path is isolated by a non-bubble tight damper.
Another outside air path connects the PV air handMng units to the OV lab hoods supply fan; this path is isolated downstream of the fan by a non-bubble tight damper.
Because of the licensee's failure tc adequately isolate the PV and OV systems, any failure which causes the OV system to become contaminated will i
subsequently contaminate the PV system artd'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 i. riegative f
pressure in the normal intake duct for the PV cnd i
OV systems, thus increasing the potential for unfiltered inleakage into both the control room and TSC..
The closing of the PV system relief dampers removes the capability of relieving excess air from the system; thus, the PV system should be modified from economizer systems to minimum outside air systems.
It appears that smoke purging of the control room would require that the doors to the turbine building be opened and portable porge fans be used.
The pressure sensing instrumentation for the control room is inadequate.
(
(During a plant tour on March 25, 1986, the inspector noted I
the control room panol pressure gauge read +.05 inch wg
)
and
.05 inch wg with the door between the control room f
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 men and the TSC was closed, independent measurements had demer.strated that the control room was being maintained at a pressure
~
of, at least, + 1.25 inch wg with respect to surrounding creas (which would satisfy the criterion of Standard Review Plan 6.4).
The 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 may have contributed to the inadequate maintenance of the control room gas-boundary.)
7
l y
)
f.
Oth the door open between the control' room and the TSC,
]
the PV system is unable to adequately pressurire the j
l control room..The licensee has ensured that procedures I
adequately specify the requirements to close the door between the control room and TSC in the event of an c
accident.
,W d
(3) On March 11,198'/, helbmi 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 WC.
The licensee had been informed of the unacceptability of this test by the inspector.
j i
d.
Long Term Corrective Action
{
J (1) Based on the PV system walkdown/ review, the licensee is I
considering several actions to enhance PV system performance, including the addition of bubble-tight dampers (See Section 5.c, Item (2)).
3 (2) The licensee is investigating the feasibility of permanent
^
modifications'to separate the PV system from the OV system.
J l
(3) Revision of the plant drawings to accurately reflect as-built conditions of the PV system.
(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 precedure, t
(5) Ensure that the control rooin gas control boundaries are, at l
1 east, +.125 inch wg with respect to adjacent areas and proper I
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 j
that the use of silicone sealant and other temporary patching 1
material on the PV system is unacceptable.
l 8
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 l
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 safety hazard.
(2) Potential Effect on Control Room Operators for Design Basis 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 licensee'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, dcring the inspector's evaluation of the event the licensee informed him that their 1981 Entech evaluation was unnecessarily conservative, and the licensee subsequently had Sargent & Lundy (S&L) perform a " realistic" evaluation of control room operator doses based on the measured inleakage values.
The evaluatioa eventually resulted in calculated thyroid doses of 10.3 rem and 15.2 rem, which are within GDC-19 limits; these results transmitted from S&L to the licensee by a letter dated April 2,1987 (attached).
Later, by letter dated May 19, 1987 (attached), the licensee 9
)
l 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 Lion controi 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 unfilterad inleakage of airborne radioactivity.
Specifically, Region III asked NRR to evaluate the acceptability of the licensee's " realistic evaluation and, a
if the evaluation was not acceptable, to determine the correct accident doses.
NRR replied in a June 4, 1987 menorandum I
-(attached) which stated the following conclusions:
The " realistic" analysis is not consistent the Standard Review Plan (SRP), and since the deviations from the SRP 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 8 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).
l 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.
f.
Reoulatory 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.
1 l
10
G
'4-
' Technical Specification 3.17.1 requires that the control room makeup air charcoal adsorber system be operable unless the system is L
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 date that the system is made inoperable.
General Design Criterion 19 of Appendix A to 10 CFR 50 requires that the control room be provided.with adequate radiation protection to permit access and occupancy of the control room under accident conditions without' personnel receiving radiation exposures in excess of five rem whole body, or its equivalent to any part of the body, for the duration of the accident.
Standard Review Plan (NUREG-0800)
Section 6.4, " Control Room Habitability Review," states that a thyroid dose of 30 rem is compatible with the GDC-19 dose guideline.
The basis for Technical Specification 3.17 states that the plant 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 personnel 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 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; 304/67005-01) 6.
Inability of the TSC Ventilation System to Perform Its Desion Requirements Design Requirements a.
Event Summary 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 radioactivity entered the TSC.
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 11
O 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.
On November 21, 1986, the licensee informed the resident inspector that their computer and miscellaneous rooms ventilation (OV) system, which supplies ventilation air to the TSC, could not be demonstrated to meet its design criteria.
The licensee found that some of the rooms supplied by the OV system were not at a positive pressure with respect to adjoining areas, resulting in the potential for air leakage into the OV system from the Auxiliary Building.
In the event of high airborne activity following an accident, the TSC could I
become uninhabitable.
b.
Event Causation 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 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 OV 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.
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 12
.O 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, 1986, the licensee began an OV system walkdown to identify other system / installation discrepancies and evaluate the effect on system safety function. On October 30, 1986, the preliminary walkdown/ review reached the following conclusion:
Although acceptance testing of the TSC construction modification began on September 8,1986, the TSC HVAC performance criteria were not adequately communicated to the field.
Specifically, it was not identified by the station personnel that the TSC was to be maintained at a positive pressure by the OV system.
By design, the section of the OV ductwork containing the relief damper, 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.
Potential inleakage pathways exist via OV 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.
The installed OV system pressurized boundary isolation dampers may not be acceptable with regards to current licensing requirements.
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.
The closing of the OV 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
0 4
'L l
0 The following drawings indicate the 0V system was not built as designed: M-77 and M-316.
l (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.
l (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 0V system could not be demonstrated to meet its design criteria; in the event of high airborne radioactivity following an accident, the TSC could become uninhabitable (Inspection Repo'rts No. 50-295/86028(DRP);
No. 59-304/86028(DRP)).
(5) On December 3, 1986, the licensee sent to all GSEP Recovery i
Managers a memorandum which stated the Zion TSC cannot be L
maintained at a positive pressure and Zion Procedure i
No. EPIP 410-1, "On-Site Support Centers, addresses actions to
]
be taken if the TSC becomes uninhabitable.
l l
(6) On March 3,1987, Sargent & Lundy provided the licensee with the results of the OV HVAC testing 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.
d.
Long Term Corrective Action (1) Based on the OV system walkdown/ review, the licensee is considering several actions to enhance OV system performance, including the addition of bubble-tight dampers (See Section 6.c, Item (2)).
l (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 OV systems.
(4) On January 19,19d7, 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.
14
l 6
e.
Safety Significance (1) Radioactive Airborne R'elease of September 11, 1986 As stated in Section 5.e, a release of this magnitude does not represent a significant health and safety hazard.
(2) Potential Effect on TSC,&ersonnel for Desion 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 currently applicable.
f.
Conclusions 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 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, 1987.
The inspector summarized the scope and findings of the inspection, 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 06/04/67 from F. J. Congel to J. A. Hind l
1 15 w_____-_______________