Transients 1

Question 1

What does 10 CFR 50.46 (ECCS (LOCA)) state?

Answer 1

• Peak Cladding Temp < 2200°F
• Max Cladding Oxidation - 17% of max cladding thickness prior to oxidation
• Max Hydrogen Generation < 1%
• Coolable Geometry
• Long-Term Cooling

Question 2

What is the ESF Performance Capability Criterion?

Answer 2

• Sufficient to accommodate the failure of any single active component without undue risk to the health and safety of the public
  1. Injection phase - one active failure
  2. Recirc phase - one active or passive failure
  3. Single Failure
  4. Redundant reactor shutdown capability

Question 3

Why the difference in failures between injection and recirculation phases and how long is long term cooling?

Answer 3

• 30 days, probability of a passive failure much greater and decay heat is much lower so are more able to recover to stay within analysis limits.

Question 4

What is the 10CFR100 def for exclusion area?

Answer 4

• Area surrounding the reactor, in which the reactor licensee has the authority to determine all activities including exclusion or removal of personnel and property from the area such that an individual located at any point on its boundary for two hours immediately following onset of the postulated fission product release would not receive a total radiation dose of > 25 REM Whole Body OR > 300 REM to the thyroid from iodine exposure

Question 5

What is the 10CFR100 def for Low Population zone?

Answer 5

• area immediately surrounding the exclusion area which contains residents, the total number and density of which are such that there is a reasonable probability that appropriate protective measures could be taken in their behalf in the event of a serious accident such that an individual located at any point on its outer boundary who is exposed to the radioactive cloud resulting from release during the entire period of its passage would not receive a total rad dose to the whole body > 25 rem or a total radiation dose > 300 rem to the thyroid from iodine exposure

Question 6

What is the 10CFR100 def for Population Center Distance?

Answer 6

• means the distance from the reactor to the nearest boundary of a densely populated center containing more than about 25,000 residents at least 1.33 times the distances from the reactor to the outer boundary of the low population zone

Question 7

What is DNB?

Answer 7

• Undesirable condition in core
• Predicted by experimental data
• DNB ratio defined as the local predicted heat flux necessary for DNB to occur (CHF) divided by actual local heat flux
• For a DNBR ≥ 1.3, 95% confidence level of 95% probability that DNB is not occurring anywhere in core

Question 8

What does the Overpower trip protect from?

Answer 8

• Protects fuel against excessive peak centerline temperatures (< 4700°F design limit would occur at high power)
• OPΔT is the backup trip

Question 9

What does the Loss of Flow Trip protect from?

Answer 9

• Provides DNB protection due to rapid core heat-up

Question 10

What does the SG Safeties protect from?

Answer 10

• Provide protection for slow reactivity addition accidents

Question 11

Why do we have S/G PORVs if we are not crediting them for transient analysis as we do the S/G safeties?

Answer 11

• Normal operational transients, (ANSI Condition I events) implicitly credit them and other design features that are not credited. Also there are design features of the plant (as described in UFSAR chapters other than Ch 14 that describe the facility and equipment features that preclude upsets that could result in higher ANSI condition events. Regulator would not have approved facility that was teetering on the verge of an upset.

Question 12

The RPS coupled with S/G safeties afford protection to which types of conditions?

Answer 12

• Condition I and II events (The RPS coupled with S/G safeties afford protection to prevent clad damage for all Cond. I and II Events (protective envelope))
• However, they cannot by themselves afford protection for Condition III and IV events

Question 13

What if S/G safeties were not available?

Answer 13

• Violation of TS, but Pressurizer safeties have sufficient capacity to prevent RCS over pressurization

Question 14

Operators should always assume that initial parameters are?

Answer 14

• within Tech Spec Limits

If outside TS limits, you may be in an unanalyzed condition

Question 15

Heat flux need to cause DNB is dependent on?

Answer 15

• Pressure
• Enthalpy
• Local flow

Question 16

What is DNBR?

Answer 16

Local Value of Critical Heat Flux (CHF)
______________________

Local actual Heat Flux

Question 17

What is the purpose of 10CFR50, Safety Analysis?

Answer 17

• Demonstrate that both units can be operated safely,
• During postulated highly unlikely occurrences,
• While ensuring the health and safety of the public.