Text

Insp Repts 50-295/87-05 & 50-304/87-05 on 870302-0610.No Violations Noted.Major Areas Inspected:Licensee Action Following Release of Airborne Radioactivity Into Control Room Technical Support Ctr
	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: ML20235L607; ML20235L612; ML20245B345;
References
	50-295-87-05, 50-295-87-5, 50-304-87-05, 50-304-87-5, NUDOCS 8707160762
	Download: ML20235L612 (18)
	v • d • e

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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

Inspector: C. F. Gill

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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 I

@R..Cascarano, Technical Staff Supervisor j

@#+*P. LeBlond, Zion Nuclear' Licensing Administrator

@+*F. Lentine, Zion Project Engineer, SNED

@#+T. Printz,. Assistant Technical Staff Supervisor l

J. Rappaport, QA Engineer

-@#+T. Rieck, Technical Services Superintendent <

C. Schultz, Regulatory Assu'rance Supervisor i

@+M. Turbak, Operating Plant Licensing Director 4

P. Eng, NRC Resident Inspector

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+*L. Greger, NRC/ Region III, Chief, FRPS ..

l +J. Hayes,,NRC/NRR, Nuclear Engineer

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+*M. Holzmer, NRC Senior Resident Inspect'or

+*W. Shafer, NRC/ Region III,. Chief, EPRPB .j

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. 1

@ 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' !

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 i

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(0 pen) Unresolved Items (295/86028-01; 304/86028-01): Control room'and 1

TSC ventilation systems unable to meet design requirements. The adequacy l'

of the as-built ventilation. systems and the. licensee's initial corrective-

actions following the incursion of noble gas into the~ control room and ;

TSC are discussed in Sections 5 and 6,.respectively. Because this H

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 1

tracked as a separate Unresolved Item (295/87005-02; 304/87005-02). j

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Licensee Event Reports (LER) Followup

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4.

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 3

action was accomplished, and corrective action to prevent recurrence had

been accomplished in accordance with Technical Specifications. The LER

l listed below is considered closed:

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l Units 1 and 2

LER NO. Description

86035 Minor Radioactive Release into Control l

Room Due to Control Room Relief Damper

Installation Deficiency.

l This LER was reviewed as part of the inspection into the apparent I

inability of the control room and TSC ventilation systems to meet their l

design requirements; these matters are discussed in Sections 5 and 6, I

respectively. I

5. Inability of the Control Room Ventilation System to Perform Its

Design Requirements

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a. Event Summary

I 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) 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 3

systems needed to shutdown the reactor and maintain a safe shutdown i

condition. According to licensee representatives, the initial i

estimation of the control room unfiltered inleakage pathway was I

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 j

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 .

unfiltered release pathway exists into PV system through the

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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.

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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. 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

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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 f

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- !

modification was disconnected and the control room ventilation .q

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.

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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

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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, 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. It is '

L 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 0.25 hours 0.00149 weeks 3.4245e-4 months , 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 0.361 hours 0.00215 weeks 4.9465e-4 months , the

postulated flow path was confirmed using a helium tracer gas

technique. At about 1700 hours0.0197 days 0.472 hours 0.00281 weeks 6.4685e-4 months , 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 1

control zone from adjacent zones or the outside should be i

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 j

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 !

PV air handling units to the OV lab hoods supply fan; this 1

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 j

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 l

capability of relieving excess air from the system; thus, l

the PV system should be modified from economizer systems l

to minimum outside air systems. It appears that smoke J

purging of the control room would require that the doors 1

to the turbine building be opened and portable purge fans {

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The pressure sensing instrunientation for the control room j

is inadequate. i

(During a plant tour on March 25, 1986, the inspector noted

the control room panel pressure gauge read + .05 inch wg !

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 i

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. ,

(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, 1

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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 evaluation eventually

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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). i

Later, by letter dated May 19, 1987 (attached), the licensee l

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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. ,

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. i

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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 0.00833 hours 4.960317e-5 weeks 1.1415e-5 months from the date1that the system is made inoperable.

General Design Criterion 19 of Appendix A to 10 CFR 50 requires

i that the control room be provided with' adequate radiation protection

.to permit access and occupancy.of.the control room under_ accident

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conditions without personnel receiving radiation exposures.in excess

[. of five tem whole body,.or its equivalent to any.part of the body,

L for the duration of the accident. Standard Review Plan (NUREG-0800)

Section 6.4, " Control Room Habitability Review," states that a

l 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-

I 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 !

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 -

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. i

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L 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, i

which supplies ventilation air to the TSC, could not be demonstrated i

to meet its design criteria. The licensee found that some of the i

rooms supplied by the OV system were not at a positive pressure with 1

respect to adjoining areas, resulting in the potential for air '

leakage into the OV system from the Auxiliary Building. In the I

event of high airborne activity following an accident, the TSC could l

become uninhabitable.

b. Event Causation l

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

l completely drained, creating the vent path into the auxiliary

building from the waste gas system.

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(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.

i c. Short Term Corrective Action

(1) On September 12, 1986, at about 1200 hours0.0139 days 0.333 hours 0.00198 weeks 4.566e-4 months , 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 0.444 hours 0.00265 weeks 6.088e-4 months , 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, i '

1986, the preliminary walkdown/ review reached the following

conclusion:

l

Although acceptance testing of the TSC construction '

modification began on September 8, 1986, the TSC HVAC

performance criteria were not adequately communicated to j

the field. Specifically, it was not identified by the j

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,

i 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.

l

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. ;

l l

l * The installed OV system pressurized boundary isolation l

dampers may not be acceptable with regards to current

licensing requirements.

The hot and cold laboratory supply fan is designed

l 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

= _ - - _ _ _ _ _ -

. . ,

,

- The following drawings indicate the 0V system was not

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

~

L 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.

l d. Long Term Corrective Action

l

(1) Based on the OV system walkdown/ review, the licensee is l

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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i

,

e. Safety Significance

(1) Radioactive Airborne Release of September 11, 1986

As stated in Section 5.e, a release of this magnitude does not i

represent a significant health and safety hazard. j

1

(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 1

currently applicable. 1

f. Conclusions >

l'

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 '

i

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, i

1987. The inspector summarized the scope and findings of the inspection, i

including the unresolved item and the apparent violation. The inspector l

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

.

15

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SARGENT & LUMDT

ENGINEE343

rovNOcc ie ,e-

55 CAST MONROE STRECT

CHICAOO, lLLINOIS 60603

(3823 269 2000 1

TwX 9fOa28t*2607

1

April 2, 1987 I '

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:

o Primary Containment spray in operation for 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months which

depleted

period

the organic and particulate iodine species in that. I

e j

Zion specific occupancy factors related to 8. hours per day

for 7 days with 2 days of f for 30 days

e

The maximum measured integrated leak' rate for either unit,- ,

i

over the last 14 years of .035%/ day for-the first 24 hour2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months 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: j

'

i

l

d

- - - - _ _. _ _ _ _ - _ _ _ _ _ _ __.

SARGENT& LUNDY

.

E N GIN E E MS l

CHICAGO . I

.

Mr. F. G. Lentine April,2, 1987

' Commonwealth Edison Company Page 2

e Primary Containment forced circulation = 1.9 5

cfm

o PrimaryContainmentfreevolume=2.715x10gx30 ft l

e Primary Containment: sprayed volume fraction _=__.3239__- _

I

e Operating power is'102% of 3250 MWth

e Initial airborne, iodine = 100% of the adjusted gap activity

as defined in FSAR Table A.2-2 1

e Iodine species 95.5% elemental, 24 particulate and 2.5% l

organic j

e Spray decontamination factor - 200 elemental j

e Basic dose modeling for the turbine and auxiliary'bu'ilding '

is the same as that in the FSAR Question 9.3, Amendment 17

- 1971

l e 154 and 236 cfm of unfiltered inleakage from A&B train

auxiliary building' dampers respectively

l e Murphy Campe wind direction factors

l 9

l 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 1

containment leakage of .1% and .035% per day for the first day

and 50% of that for the duration, 30 days total. From Table 2, i

with the above stated conditions and assumptions, the calculated j

thyroid doses are below the GDC 19 limit of 30 rem. j

Yours very truly,

1

B. Schwartz i

Senior Shielding 1

'C.

!lg! Project Engineer l

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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..

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l

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TABLE 1

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Control 1<oom 30 Day Dose Summary Using Zion i

l

Control Room Occupancy Murphy Campe Wind Direction Factors and' )

Design Containment Leakage

1

Control !

. Control Room Control Control Room 30 Day' . Room l

Infiltration Room Dose, Rem, 30 Day j

Rate, cfm, from Filter Contributions from the Tetal

Aux. Efficiency, Aux. Turbine Dose,.-

Bldg. Percent Dose Type Bldg. Bldg. Rem

154 99.99 Thyroid 29.4 .01 _29.4 i

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. Rem

154 99.99 Thyroid 10.3 .01 10.3

-1

l

236 99.99 Thyroid 15.2 0.0 15 '. 2 ' j

i

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,m

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/ Commonwealth Edison !

!

s

7;

~~'

i)7One First National Plaza. CNeago. !!hnois

Address Reply to. Post Offca Box 767

'%j CNeago, Ithnois 60690 0767 ,

1

.

PRf02in tourtro l

Q"

'

gruul '

May 19, 1987 y f$

~

3R5 ,[ ~ '

I

MR. b

-

G V) * u

-

a

Mr. A. Bert Davis mg

Regional Administrator

U.S. Nuclear Regulatory Commission

Region III

~799 Roosevelt Road

Glen Ellyn, IL 60137

l

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 l

at Zion Station. These calculations were performed at the request of C.F.

Gill of your office. l

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

. .

,

.

,

..

A.B. Davis -2- May 19, 1987

l

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, l

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 l

'

this office.

very truly yours,

hP.C. LeBlond

$<

Nuclear Licensing Administrator

cc: Resident Inspector

J.A. Norris - NRR

l

3068K

-

)

ML20235L612

Text

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