ML17139C753

Safety Evaluation Supporting Exemption from 10CFR50.44 Re Containment Inerting

ML17139C753
Person / Time
Site:	Susquehanna
Issue date:	12/19/1984
From:	Office of Nuclear Reactor Regulation
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ML17139C752	List: ML17139C751 ML17139C753 ML17139C754
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NUDOCS 8412260104
Download: ML17139C753 (9)

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':;r SW>'c>Tax, c C. r"OSS SAFETY EVALUATION BY THE OFFICE OF NUCLEAR PEACTOR REGULATION SUPPORT EXEMPTION FROM 10 CFR 50.44 FACILITY OPERATING LICENSE NO.

NPF-22 PENNSYLVANIA POWER AND LIGHT COMPANY LUZERNE COUNTY, PENNSYLVANIA SUS(}UEHANNA STEAM ELECTRIC STATION UNIT 2 (SSES-2)

DOCKET NO. 50-388 Introduction I

, Inerting the containment for the SSES-2 plant is required by 10 CFR 50.44 (revised).

In 10 CFR 50 '4, "Standards for Combustible Gas Control System in Light Water Cooled Power Reactors,"

Section 50.44 (c).{3).(i) states in part that, "Effective May 4, 1982 or 6 months after initial criticality, whichever is later, an inerted atmosphere shall be provided for each boiling light-water nuclear power reactor with a Mark I or Mark II type containment."

Evaluation Since SSES-2 achieved its initial criticality on May 7, 1984, the plant is required to be inerted by November 8, 1984, per the 10 CFR 50.44 requirement set forth above.

On October 27, 1984 SSES-2 shut-down for the precommercial outage scheduled to last through the end of December, 1984.

Prior to start-up in January 1985, the licensee needs the exemption in order to complete about 2-3 weeks of the power ascension testing program (PATP).

This requires that the licensee receive a temporary exemption from the requirement of 10 CFR 50.44 so that it may continue operating the plant with a non-inerted containment during the balance of the initial startup test program as originally planned.

The proposed exemption from the regulation is required in order to complete the balance of the PATP in accordance with the licensee's test plan.

The licensee's test plan is based on maintaining the containment in a non-inerted condition until after completing the 100% rated thermal trip test, a condition which normally would be expected to occur within about 120 effective full power days of core burn-up.

No changes are being made in maximum'full power days of core burn-up normally expected be ore inerting is required.

In fact to assure this, the maximum expected value of 120.effective full power days is made part of the proposed action.

The licensee's PATP schedule has not been maintained as originally planned.

This has resulted in a simple stretch out to the time required to complete all poCt criticality PATP tests.

It is advantageous to operate the reactor without inerting during the

PATP, as an uninerted containment would permit unscheduled inspections or identi-84i2260i04 84i2i9 PDR ADaCX 05OOOS88 PDR

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fication of possible problems important to safety =during this period.

The anticipated high frequency of containment entries during the PATP period and the required deinerting and re-inerting time (about 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />) would tend to discourage early and frequer t containment entries for identifying and correcting any potential sa ety problems before they become serious safety problems.

Further, the NRC staff believes, that to now require inerting before the PATP tests have been completed could result in less assurance of safety, because of the added time and/or decreased ability to directly examine and evaluate components and systems inside containment while the PATP tests are under way.

Completing the PATP tests with an uninerted containment

'(exemption granted) then would reduce the likelihood of development of an event requiring protec-tive safety actions both during the period of exemption and later.

Because of the low level of fission product inventory during the PATP period, (less than 42 ef ective full power days at present increasing to'he maximum of only 120 FPD) and the short duration anticipated for the exemption (about 2-3 weeks after start-up),

there is an extremely low likelihood that the inerting system would be required.

Based on the information provided by the licensee and the staff's assurance that the remainder of the PATP tests will be performed in essentially the same manner as originally planned with respect to the magnitude and duration of power levels for each remaining PATP test, the NRC staff concludes that there will be no increase in the risks of operation through completion of the PATP tests with the proposed limited exemption regarding initial inerting over the risks that were contemplated for the duration of the PATP tests at the time the plant was licensed.

Therefore, since there is no perceived increase in risk by the mere fact of extending the time allowed for completion of the PATP tests under uninerted conditions, the NRC staff finds that operation would be as safe under the conditions proposed by the exemptiori as it would have been had the test been completed in the shorter calendar time of six months after initial criticality..

After the containment has once been inerted, inspection personnel entering the containment after it has then been deinerted may be in some danger, because of the possibility that non-breathable nitrogen pockets may remain if the operator fails to initiate the mixing system.

These risks are minimized during normal plant operation.

However, during PATP, the risk is greater due to the large number of personnel entries into the containment.

The inerting requirement resulted from a staff judgement that the safety benefits attributable to having an inerted containment during normal opera-tions outweighed the associated disadvantages.

This judgement does not prevail during the PATP because of the need for frequent containment entries for inspection and surveillance purposes.

The staff finds that the proposed exemption from 10 CFR 50.44, paragraph (c)(3)(i) is acceptable.

With regard to the stage of the facility's life, SSES-2 construction is complete and the PATP is in progress.

Absent. the exemption and consequent authorization to continue the PATP with deinerted containment atmosphere, access to containment will be severely restricted.

Frequent containment entries are required during PATP to adjust control

systems, calibrate instruments and monitor containment conditions as the plant ascends in power.

Without the requested exemption, considerable delay to deinert and reinert before and after containment entries will be encountered.

At this point in the PATP, to require inerting would significantly extend the time to complete the PATP, and, therefore, delay commercial operation.

The stage of the facility's life would appear to favor issuance of the exemption.

I I

The regulatory requirement from which the exemption is sought anticipated that-power ascension test programs could be completed within six months and consequently the core fission product inventory that would build up over the life of the program was acceptable.

While the regulation contemplated a

six month period, typical BWR programs have proven to actually require an average of 330 days.

With this simple stretch in time, no significant increase in core inventory occurs and the same effective core history is experienced.

Accordingly, for the reasons stated

above, frequent containment

entries, and the potential danger to the health and safety of plant operators, the staff finds that the containment should remain deinerted until completion of the PATP.

Therefore, the equities lie in favor of granting the exemption.

Finally, while the public interest favors adherence to the Commission's regulations, the staff has concluded that in this instance an exemp-tion from compliance with 10 CFR 50.44 for containment inerting has no adverse safety significance (as noted above).

Therefore, the granting of this exemption will have no effect on the public health and safety and will also promote efficient and expeditious testing of facility components and

systems, and should therefore be granted.

The staff has concluded that the exemption from the requirements of 10 CFR 50.44 paragraph (c).(3).(i) as discussed above is authorized by law, will not endanger life or property or the common defense and security and is other-wise in the public interest.

This involves an exemption from the requirement of 10 CFR 50.44.

Because an exemption is involved, pursuant to 10 CFR 51.21, an environmental assessment and finding of no significant impact was prepared in connection with the issuance of this exemption.

Conclusion Based on the considerations discussed

above, we have concluded that the proposed temporary exemption from 10 CFR 50.44(c)(3)(i) is authorized by law, will not endanger life or property or the common defense and is otherwise in the public interest and should be granted.

Dated:

December 19, 1984 Previous concurrences concurred on by*:

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Without the requested exemption, considerable delay to deinert and reinert before and after containment entries will be encountered.

At this point in the PATP, to require inerting would significantly extend the time to complete the PATP and, therefore, delay commercial operation.

The stage of the facility's life would appear to favor issuance of the exemption.

The regulatory requirement from which the exemption is sought anticipated that power ascension test programs could be completed within six months and consequently the core fission product inventory that would build up over the life of the program was acceptable.

While the regulation contemplated a

six month period, typical BWR programs have proven to actually require an average of 330 days.

With this simple stretch in time, no significant increase in core inventory occurs and the same effective core history is experienced.

Accordingly, for the reasons stated above, frequent containment

entries, and the potential danger to the health and safety of plant operators, the staff finds that the containment should remain deinerted until completion of the PATP.

Therefore, the equities lie in favor of granting the exemption.

Finally, while the public interest favors adherence to the Commission's regulations, the staff has concluded that in this instance an exemp-tion from compliance with 10 CFR 50.44 for containment inerting has no adverse safety significance (as noted above).

Therefore, the granting of this exemption will have no effect on the public health and safety and will also promote efficient and expeditious testing of facility components and

systems, and should therefore be granted.

The staff has concluded that the exemption from the requirements of 10 CFR 50.44 paragraph (c).(3).(i) as discussed above is authorized by law, will not endanger life or property or the common defense and security and is other-wise in the public interest.

This involves an exemption from the requirement of 10 CFR 50.44.

Because an exemption is involved, pursuant to 10 CFR 51.21, an environmental assessment and finding of no significant impact was prepared in connection with the, issuance of this exemption.

Conclusion With respect to this e emption, we have

oncluded, based on~the considerations discu sed above,'that, there is reasonabl assurance that th+health and safety of the ublic wil ot b e

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d security of the health and safety of the public.

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instruments and monitor containment conditions as the plant ascends in power.

Without the requested exemption, considerable delay to deinert and reinert before and after containment entries will be encountered.

At this point in the PATP, to require inerting would significantly extend the time to complete the PATP and, therefore, delay commercial operation.

The stage of the facility's life would appear to favor issuance of the exemption.

No internal inconsistencies in the regulation are apparent and in this

instance, this factor appears to weigh neither in favor or nor against a

finding of exigent circumstances and issuance of the exemption.

The regulatory requirement form which the exemption is sought anticipated that power ascension test programs could be completed within six months and consequently the core fission product inventory that would build up over the life of the program was acceptable.

While the regulation contemplated a

six month period, typical BWR programs have proven to actually require an average of 330 days.

With this sample stretch in time, no significant increase in core inventory occurs and the same effective core';,history is experienced.

Accordingly, for the reasons stated above, frequent containment

entries, and the potential danger to the health and safety of plant operators, the staff finds that the containment should remain deinerted until completion of the PATP.

Therefore, the equities lie in favor of granting the exemption.

Finally, while the public interest favors adherence to the Commission's regulations, the staff has concluded that in this instance, where an exemp-tion from compliance with 10 CFR 50.44 for containment inerting has no adverse safety significance (as noted above).

Therefore, the granting of this exemption will have no effect on the public health and safety and will also efficient and expeditious testing of facility components and

systems, and should therefore be granted.

The staff has.concluded that the exemption form the requirements of 10 CFR 50.44 paragraph (c).(3).(i) as discussed above is authorized by law, will not endanger life or property or the common defense and security and is other-wise in the public interest.

This involves an exemption form the requirement of 10 CFR 50.44.

Because an exemption is involved, pursuant to 10 CFR 51.21, an environmental assessment and finding of no, significant impact was prepared in connection with the issuance of this exemption.

Conclusion With respect to this exemption, we 'have concluded, based on he considerations discus ed above, tha

'there is reasonabl assurance that the health and safety of the ublic will not be endangered by op ration in the propo d manner, and such act vitiescijiiTi'h'e"o'nducted in'oiiipli ce with the'c'oiiimtss on's n~ul>- p

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